nfsantos commented on code in PR #860:
URL: https://github.com/apache/jackrabbit-oak/pull/860#discussion_r1124641325


##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene

Review Comment:
   ```suggestion
    * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from Lucene
   ```



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }

Review Comment:
   Similar here using `Map.of()`



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))
+                    )));
+                }
+                return builder;
+            }
+        }
+        return null;
+    }
+
+    @NotNull
+    private static TokenizerDefinition loadTokenizer(NodeState state) {
+        String name = 
normalize(Objects.requireNonNull(state.getString(FulltextIndexConstants.ANL_NAME)));
+        Map<String, Object> args = convertNodeState(state);
+        args.put(ANALYZER_TYPE, name);
+        return new TokenizerDefinition(name, JsonData.of(args));
+    }
+
+    private static <FD> LinkedHashMap<String, FD> loadFilters(NodeState state,
+                                                              Function<String, 
Class<? extends AbstractAnalysisFactory>> lookup,
+                                                              
BiFunction<String, JsonData, FD> factory) {
+        LinkedHashMap<String, FD> filters = new LinkedHashMap<>();
+        int i = 0;
+        Tree tree = TreeFactory.createReadOnlyTree(state);
+        for (Tree t : tree.getChildren()) {
+            NodeState child = state.getChildNode(t.getName());
+            Class<? extends AbstractAnalysisFactory> tff = 
lookup.apply(t.getName());
+            String name;
+            try {
+                name = normalize((String) tff.getField("NAME").get(null));
+            } catch (Exception e) {
+                LOG.warn("unable to get the filter name using reflection. Try 
using the normalized node name", e);
+                name = normalize(t.getName());
+            }
+            Optional<Map<String, String>> mappingOpt =
+                    CONFIGURATION_MAPPING.entrySet().stream().filter(k -> 
k.getKey().isAssignableFrom(tff)).map(Map.Entry::getValue).findFirst();
+            Map<String, Object> args = convertNodeState(child, 
mappingOpt.orElseGet(Collections::emptyMap));
+
+            args.put(ANALYZER_TYPE, name);
+
+            filters.put(name + "_" + i++, factory.apply(name, 
JsonData.of(args)));

Review Comment:
   Nitpick: I find the usage of the i++ increment operator inside the string 
concatenation confusing and error-prone. Suggest moving the increment to a 
separate line after the `.put` call. 



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))
+                    )));
+                }
+                return builder;
+            }
+        }
+        return null;
+    }
+
+    @NotNull
+    private static TokenizerDefinition loadTokenizer(NodeState state) {
+        String name = 
normalize(Objects.requireNonNull(state.getString(FulltextIndexConstants.ANL_NAME)));
+        Map<String, Object> args = convertNodeState(state);
+        args.put(ANALYZER_TYPE, name);
+        return new TokenizerDefinition(name, JsonData.of(args));
+    }
+
+    private static <FD> LinkedHashMap<String, FD> loadFilters(NodeState state,
+                                                              Function<String, 
Class<? extends AbstractAnalysisFactory>> lookup,
+                                                              
BiFunction<String, JsonData, FD> factory) {
+        LinkedHashMap<String, FD> filters = new LinkedHashMap<>();
+        int i = 0;
+        Tree tree = TreeFactory.createReadOnlyTree(state);
+        for (Tree t : tree.getChildren()) {
+            NodeState child = state.getChildNode(t.getName());
+            Class<? extends AbstractAnalysisFactory> tff = 
lookup.apply(t.getName());
+            String name;
+            try {
+                name = normalize((String) tff.getField("NAME").get(null));
+            } catch (Exception e) {
+                LOG.warn("unable to get the filter name using reflection. Try 
using the normalized node name", e);
+                name = normalize(t.getName());
+            }
+            Optional<Map<String, String>> mappingOpt =
+                    CONFIGURATION_MAPPING.entrySet().stream().filter(k -> 
k.getKey().isAssignableFrom(tff)).map(Map.Entry::getValue).findFirst();

Review Comment:
   Break up this line to make it more legible.



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))
+                    )));
+                }
+                return builder;
+            }
+        }
+        return null;
+    }
+
+    @NotNull
+    private static TokenizerDefinition loadTokenizer(NodeState state) {
+        String name = 
normalize(Objects.requireNonNull(state.getString(FulltextIndexConstants.ANL_NAME)));
+        Map<String, Object> args = convertNodeState(state);
+        args.put(ANALYZER_TYPE, name);
+        return new TokenizerDefinition(name, JsonData.of(args));
+    }
+
+    private static <FD> LinkedHashMap<String, FD> loadFilters(NodeState state,
+                                                              Function<String, 
Class<? extends AbstractAnalysisFactory>> lookup,
+                                                              
BiFunction<String, JsonData, FD> factory) {
+        LinkedHashMap<String, FD> filters = new LinkedHashMap<>();
+        int i = 0;
+        Tree tree = TreeFactory.createReadOnlyTree(state);
+        for (Tree t : tree.getChildren()) {
+            NodeState child = state.getChildNode(t.getName());
+            Class<? extends AbstractAnalysisFactory> tff = 
lookup.apply(t.getName());
+            String name;
+            try {
+                name = normalize((String) tff.getField("NAME").get(null));
+            } catch (Exception e) {
+                LOG.warn("unable to get the filter name using reflection. Try 
using the normalized node name", e);
+                name = normalize(t.getName());
+            }
+            Optional<Map<String, String>> mappingOpt =
+                    CONFIGURATION_MAPPING.entrySet().stream().filter(k -> 
k.getKey().isAssignableFrom(tff)).map(Map.Entry::getValue).findFirst();
+            Map<String, Object> args = convertNodeState(child, 
mappingOpt.orElseGet(Collections::emptyMap));

Review Comment:
   Move the `orElseGet` to be the last operation in the chain in the line 
above. I think it conveys better the intention of the code.



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))
+                    )));
+                }
+                return builder;
+            }
+        }
+        return null;
+    }
+
+    @NotNull
+    private static TokenizerDefinition loadTokenizer(NodeState state) {
+        String name = 
normalize(Objects.requireNonNull(state.getString(FulltextIndexConstants.ANL_NAME)));
+        Map<String, Object> args = convertNodeState(state);
+        args.put(ANALYZER_TYPE, name);
+        return new TokenizerDefinition(name, JsonData.of(args));
+    }
+
+    private static <FD> LinkedHashMap<String, FD> loadFilters(NodeState state,
+                                                              Function<String, 
Class<? extends AbstractAnalysisFactory>> lookup,
+                                                              
BiFunction<String, JsonData, FD> factory) {
+        LinkedHashMap<String, FD> filters = new LinkedHashMap<>();
+        int i = 0;
+        Tree tree = TreeFactory.createReadOnlyTree(state);
+        for (Tree t : tree.getChildren()) {
+            NodeState child = state.getChildNode(t.getName());
+            Class<? extends AbstractAnalysisFactory> tff = 
lookup.apply(t.getName());
+            String name;
+            try {
+                name = normalize((String) tff.getField("NAME").get(null));
+            } catch (Exception e) {
+                LOG.warn("unable to get the filter name using reflection. Try 
using the normalized node name", e);
+                name = normalize(t.getName());
+            }
+            Optional<Map<String, String>> mappingOpt =
+                    CONFIGURATION_MAPPING.entrySet().stream().filter(k -> 
k.getKey().isAssignableFrom(tff)).map(Map.Entry::getValue).findFirst();
+            Map<String, Object> args = convertNodeState(child, 
mappingOpt.orElseGet(Collections::emptyMap));
+
+            args.put(ANALYZER_TYPE, name);
+
+            filters.put(name + "_" + i++, factory.apply(name, 
JsonData.of(args)));
+        }
+        return filters;
+    }
+
+    private static List<String> loadContent(NodeState file, String name) 
throws IOException {
+        List<String> result = new ArrayList<>();
+        Blob blob = ConfigUtil.getBlob(file, name);
+        Reader content = null;
+        try {
+            content = new 
InputStreamReader(Objects.requireNonNull(blob).getNewStream(), 
StandardCharsets.UTF_8);
+            BufferedReader br = null;
+            try {
+                br = new BufferedReader(content);
+                String word;
+                while ((word = br.readLine()) != null) {
+                    result.add(word.trim());
+                }
+            } finally {
+                IOUtils.close(br);
+            }
+            return result;
+        } finally {
+            IOUtils.close(content);
+        }

Review Comment:
   Any reason for not using try-with-resources?
   
   `BufferedReader.lines()` could be a simpler alternative the while loop.



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))
+                    )));
+                }
+                return builder;
+            }
+        }
+        return null;
+    }
+
+    @NotNull
+    private static TokenizerDefinition loadTokenizer(NodeState state) {
+        String name = 
normalize(Objects.requireNonNull(state.getString(FulltextIndexConstants.ANL_NAME)));
+        Map<String, Object> args = convertNodeState(state);
+        args.put(ANALYZER_TYPE, name);
+        return new TokenizerDefinition(name, JsonData.of(args));
+    }
+
+    private static <FD> LinkedHashMap<String, FD> loadFilters(NodeState state,
+                                                              Function<String, 
Class<? extends AbstractAnalysisFactory>> lookup,
+                                                              
BiFunction<String, JsonData, FD> factory) {
+        LinkedHashMap<String, FD> filters = new LinkedHashMap<>();
+        int i = 0;
+        Tree tree = TreeFactory.createReadOnlyTree(state);
+        for (Tree t : tree.getChildren()) {
+            NodeState child = state.getChildNode(t.getName());
+            Class<? extends AbstractAnalysisFactory> tff = 
lookup.apply(t.getName());
+            String name;
+            try {
+                name = normalize((String) tff.getField("NAME").get(null));
+            } catch (Exception e) {
+                LOG.warn("unable to get the filter name using reflection. Try 
using the normalized node name", e);
+                name = normalize(t.getName());
+            }
+            Optional<Map<String, String>> mappingOpt =
+                    CONFIGURATION_MAPPING.entrySet().stream().filter(k -> 
k.getKey().isAssignableFrom(tff)).map(Map.Entry::getValue).findFirst();
+            Map<String, Object> args = convertNodeState(child, 
mappingOpt.orElseGet(Collections::emptyMap));
+
+            args.put(ANALYZER_TYPE, name);
+
+            filters.put(name + "_" + i++, factory.apply(name, 
JsonData.of(args)));
+        }
+        return filters;
+    }
+
+    private static List<String> loadContent(NodeState file, String name) 
throws IOException {
+        List<String> result = new ArrayList<>();
+        Blob blob = ConfigUtil.getBlob(file, name);
+        Reader content = null;
+        try {
+            content = new 
InputStreamReader(Objects.requireNonNull(blob).getNewStream(), 
StandardCharsets.UTF_8);
+            BufferedReader br = null;
+            try {
+                br = new BufferedReader(content);
+                String word;
+                while ((word = br.readLine()) != null) {
+                    result.add(word.trim());
+                }
+            } finally {
+                IOUtils.close(br);
+            }
+            return result;
+        } finally {
+            IOUtils.close(content);
+        }
+    }
+
+    /**
+     * Normalizes one of the following values:
+     * - lucene class (eg: org.apache.lucene.analysis.en.EnglishAnalyzer -> 
english)
+     * - lucene name (eg: Standard -> standard)
+     * into the elasticsearch compatible value
+     */
+    private static String normalize(String value) {
+        // this might be a full class, let's tokenize the value
+        String[] anlClassTokens = value.split("\\.");
+        // and take the last part
+        String name = anlClassTokens[anlClassTokens.length - 1];
+        // all options in elastic are in snake case
+        name = CaseFormat.UPPER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, name);
+        // if it ends with analyzer we need to get rid of it
+        if (name.endsWith("_analyzer")) {
+            name = name.replace("_analyzer", "");

Review Comment:
   ```suggestion
          name = name.substring(0, name.length() - "_analyzer".length());
   ```
   It is safer, just in case name contains `_analyzer` more than once.



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticIndexHelper.java:
##########
@@ -123,41 +124,48 @@ private static ObjectBuilder<IndexSettings> 
loadSettings(@NotNull IndexSettings.
         if (indexDefinition.getSimilarityProperties().size() > 0) {
             builder.otherSettings(ElasticIndexDefinition.ELASTIKNN, 
JsonData.of(true));
         }
+
+        // collect analyzer settings
+        IndexSettingsAnalysis.Builder analyzerBuilder =
+                
ElasticCustomAnalyzer.buildCustomAnalyzers(indexDefinition.getAnalyzersNodeState(),
 "oak_analyzer");
+        if (analyzerBuilder == null) {
+            analyzerBuilder = new IndexSettingsAnalysis.Builder()
+                    .filter("oak_word_delimiter_graph_filter",

Review Comment:
   Create a constant for this string, it is used in other parts of the code.



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))

Review Comment:
   ```suggestion
                                       
.filter(List.copyOf(tokenFilters.keySet()))
                                       
.charFilter(List.copyOf(charFilters.keySet()))
   ```



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.

Review Comment:
   ```suggestion
    * to Elasticsearch configuration options.
   ```



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))
+                    )));
+                }
+                return builder;
+            }
+        }
+        return null;
+    }
+
+    @NotNull
+    private static TokenizerDefinition loadTokenizer(NodeState state) {
+        String name = 
normalize(Objects.requireNonNull(state.getString(FulltextIndexConstants.ANL_NAME)));
+        Map<String, Object> args = convertNodeState(state);
+        args.put(ANALYZER_TYPE, name);
+        return new TokenizerDefinition(name, JsonData.of(args));
+    }
+
+    private static <FD> LinkedHashMap<String, FD> loadFilters(NodeState state,
+                                                              Function<String, 
Class<? extends AbstractAnalysisFactory>> lookup,
+                                                              
BiFunction<String, JsonData, FD> factory) {
+        LinkedHashMap<String, FD> filters = new LinkedHashMap<>();
+        int i = 0;
+        Tree tree = TreeFactory.createReadOnlyTree(state);
+        for (Tree t : tree.getChildren()) {
+            NodeState child = state.getChildNode(t.getName());
+            Class<? extends AbstractAnalysisFactory> tff = 
lookup.apply(t.getName());
+            String name;
+            try {
+                name = normalize((String) tff.getField("NAME").get(null));
+            } catch (Exception e) {
+                LOG.warn("unable to get the filter name using reflection. Try 
using the normalized node name", e);
+                name = normalize(t.getName());
+            }
+            Optional<Map<String, String>> mappingOpt =
+                    CONFIGURATION_MAPPING.entrySet().stream().filter(k -> 
k.getKey().isAssignableFrom(tff)).map(Map.Entry::getValue).findFirst();
+            Map<String, Object> args = convertNodeState(child, 
mappingOpt.orElseGet(Collections::emptyMap));
+
+            args.put(ANALYZER_TYPE, name);
+
+            filters.put(name + "_" + i++, factory.apply(name, 
JsonData.of(args)));
+        }
+        return filters;
+    }
+
+    private static List<String> loadContent(NodeState file, String name) 
throws IOException {
+        List<String> result = new ArrayList<>();
+        Blob blob = ConfigUtil.getBlob(file, name);
+        Reader content = null;
+        try {
+            content = new 
InputStreamReader(Objects.requireNonNull(blob).getNewStream(), 
StandardCharsets.UTF_8);
+            BufferedReader br = null;
+            try {
+                br = new BufferedReader(content);
+                String word;
+                while ((word = br.readLine()) != null) {
+                    result.add(word.trim());
+                }
+            } finally {
+                IOUtils.close(br);
+            }
+            return result;
+        } finally {
+            IOUtils.close(content);
+        }
+    }
+
+    /**
+     * Normalizes one of the following values:
+     * - lucene class (eg: org.apache.lucene.analysis.en.EnglishAnalyzer -> 
english)
+     * - lucene name (eg: Standard -> standard)
+     * into the elasticsearch compatible value
+     */
+    private static String normalize(String value) {
+        // this might be a full class, let's tokenize the value
+        String[] anlClassTokens = value.split("\\.");
+        // and take the last part
+        String name = anlClassTokens[anlClassTokens.length - 1];

Review Comment:
   Check if `anlClassTokens` is not empty and raise an exception with a clear 
message, to avoid an ArrayOutOfBoundsException in case of bad input to this 
method.



##########
oak-search-elastic/src/main/java/org/apache/jackrabbit/oak/plugins/index/elastic/index/ElasticCustomAnalyzer.java:
##########
@@ -0,0 +1,254 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.jackrabbit.oak.plugins.index.elastic.index;
+
+import co.elastic.clients.elasticsearch._types.analysis.Analyzer;
+import co.elastic.clients.elasticsearch._types.analysis.CharFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.CustomAnalyzer;
+import co.elastic.clients.elasticsearch._types.analysis.TokenFilterDefinition;
+import co.elastic.clients.elasticsearch._types.analysis.TokenizerDefinition;
+import co.elastic.clients.elasticsearch.indices.IndexSettingsAnalysis;
+import co.elastic.clients.json.JsonData;
+import com.google.common.base.CaseFormat;
+import org.apache.commons.io.IOUtils;
+import org.apache.jackrabbit.JcrConstants;
+import org.apache.jackrabbit.oak.api.Blob;
+import org.apache.jackrabbit.oak.api.Tree;
+import org.apache.jackrabbit.oak.api.Type;
+import org.apache.jackrabbit.oak.plugins.index.search.FulltextIndexConstants;
+import org.apache.jackrabbit.oak.plugins.index.search.util.ConfigUtil;
+import org.apache.jackrabbit.oak.plugins.tree.factories.TreeFactory;
+import org.apache.jackrabbit.oak.spi.state.ChildNodeEntry;
+import org.apache.jackrabbit.oak.spi.state.NodeState;
+import org.apache.jackrabbit.oak.spi.state.NodeStateUtils;
+import org.apache.lucene.analysis.charfilter.MappingCharFilterFactory;
+import org.apache.lucene.analysis.en.AbstractWordsFileFilterFactory;
+import org.apache.lucene.analysis.util.AbstractAnalysisFactory;
+import org.apache.lucene.analysis.util.CharFilterFactory;
+import org.apache.lucene.analysis.util.TokenFilterFactory;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.Set;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * Loads custom analysis index settings from a JCR NodeState. It also takes 
care of required transformations from lucene
+ * to elasticsearch configuration options.
+ */
+public class ElasticCustomAnalyzer {
+
+    private static final Logger LOG = 
LoggerFactory.getLogger(ElasticCustomAnalyzer.class);
+
+    private static final String ANALYZER_TYPE = "type";
+
+    private static final Set<String> IGNORE_PROP_NAMES = new 
HashSet<>(Arrays.asList(
+            AbstractAnalysisFactory.LUCENE_MATCH_VERSION_PARAM,
+            FulltextIndexConstants.ANL_CLASS,
+            FulltextIndexConstants.ANL_NAME,
+            JcrConstants.JCR_PRIMARYTYPE)
+    );
+
+    /*
+     * Mappings for lucene options not available anymore to supported elastic 
counterparts
+     */
+    private static final Map<Class<? extends AbstractAnalysisFactory>, 
Map<String, String>> CONFIGURATION_MAPPING;
+
+    static {
+        CONFIGURATION_MAPPING = new LinkedHashMap<>();
+        CONFIGURATION_MAPPING.put(AbstractWordsFileFilterFactory.class, 
Collections.singletonMap("words", "stopwords"));
+        CONFIGURATION_MAPPING.put(MappingCharFilterFactory.class, 
Collections.singletonMap("mapping", "mappings"));
+    }
+
+    @Nullable
+    public static IndexSettingsAnalysis.Builder buildCustomAnalyzers(NodeState 
state, String analyzerName) {
+        if (state != null) {
+            NodeState defaultAnalyzer = 
state.getChildNode(FulltextIndexConstants.ANL_DEFAULT);
+            if (defaultAnalyzer.exists()) {
+                IndexSettingsAnalysis.Builder builder = new 
IndexSettingsAnalysis.Builder();
+                Map<String, Object> analyzer = 
convertNodeState(defaultAnalyzer);
+                String builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_CLASS);
+                if (builtIn == null) {
+                    builtIn = 
defaultAnalyzer.getString(FulltextIndexConstants.ANL_NAME);
+                }
+                if (builtIn != null) {
+                    analyzer.put(ANALYZER_TYPE, normalize(builtIn));
+
+                    // content params, usually stop words
+                    for (ChildNodeEntry nodeEntry : 
defaultAnalyzer.getChildNodeEntries()) {
+                        try {
+                            analyzer.put(normalize(nodeEntry.getName()), 
loadContent(nodeEntry.getNodeState(), nodeEntry.getName()));
+                        } catch (IOException e) {
+                            throw new IllegalStateException("Unable to load 
content for node entry " + nodeEntry.getName(), e);
+                        }
+                    }
+
+                    builder.analyzer(analyzerName, new Analyzer(null, 
JsonData.of(analyzer)));
+                } else { // try to compose the analyzer
+                    builder.tokenizer("custom_tokenizer", tb ->
+                            
tb.definition(loadTokenizer(defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_TOKENIZER))));
+
+                    LinkedHashMap<String, TokenFilterDefinition> tokenFilters 
= loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_FILTERS),
+                            TokenFilterFactory::lookupClass, 
TokenFilterDefinition::new
+                    );
+                    tokenFilters.forEach((key, value) -> builder.filter(key, 
fn -> fn.definition(value)));
+
+                    LinkedHashMap<String, CharFilterDefinition> charFilters = 
loadFilters(
+                            
defaultAnalyzer.getChildNode(FulltextIndexConstants.ANL_CHAR_FILTERS),
+                            CharFilterFactory::lookupClass, 
CharFilterDefinition::new
+                    );
+                    charFilters.forEach((key, value) -> 
builder.charFilter(key, fn -> fn.definition(value)));
+
+                    builder.analyzer(analyzerName, bf -> 
bf.custom(CustomAnalyzer.of(cab ->
+                            cab.tokenizer("custom_tokenizer")
+                                    .filter(new 
ArrayList<>(tokenFilters.keySet()))
+                                    .charFilter(new 
ArrayList<>(charFilters.keySet()))
+                    )));
+                }
+                return builder;
+            }
+        }
+        return null;
+    }
+
+    @NotNull
+    private static TokenizerDefinition loadTokenizer(NodeState state) {
+        String name = 
normalize(Objects.requireNonNull(state.getString(FulltextIndexConstants.ANL_NAME)));
+        Map<String, Object> args = convertNodeState(state);
+        args.put(ANALYZER_TYPE, name);
+        return new TokenizerDefinition(name, JsonData.of(args));
+    }
+
+    private static <FD> LinkedHashMap<String, FD> loadFilters(NodeState state,
+                                                              Function<String, 
Class<? extends AbstractAnalysisFactory>> lookup,
+                                                              
BiFunction<String, JsonData, FD> factory) {
+        LinkedHashMap<String, FD> filters = new LinkedHashMap<>();
+        int i = 0;
+        Tree tree = TreeFactory.createReadOnlyTree(state);
+        for (Tree t : tree.getChildren()) {
+            NodeState child = state.getChildNode(t.getName());
+            Class<? extends AbstractAnalysisFactory> tff = 
lookup.apply(t.getName());
+            String name;
+            try {
+                name = normalize((String) tff.getField("NAME").get(null));
+            } catch (Exception e) {
+                LOG.warn("unable to get the filter name using reflection. Try 
using the normalized node name", e);
+                name = normalize(t.getName());
+            }
+            Optional<Map<String, String>> mappingOpt =
+                    CONFIGURATION_MAPPING.entrySet().stream().filter(k -> 
k.getKey().isAssignableFrom(tff)).map(Map.Entry::getValue).findFirst();
+            Map<String, Object> args = convertNodeState(child, 
mappingOpt.orElseGet(Collections::emptyMap));
+
+            args.put(ANALYZER_TYPE, name);
+
+            filters.put(name + "_" + i++, factory.apply(name, 
JsonData.of(args)));
+        }
+        return filters;
+    }
+
+    private static List<String> loadContent(NodeState file, String name) 
throws IOException {
+        List<String> result = new ArrayList<>();
+        Blob blob = ConfigUtil.getBlob(file, name);
+        Reader content = null;
+        try {
+            content = new 
InputStreamReader(Objects.requireNonNull(blob).getNewStream(), 
StandardCharsets.UTF_8);
+            BufferedReader br = null;
+            try {
+                br = new BufferedReader(content);
+                String word;
+                while ((word = br.readLine()) != null) {
+                    result.add(word.trim());
+                }
+            } finally {
+                IOUtils.close(br);
+            }
+            return result;
+        } finally {
+            IOUtils.close(content);
+        }
+    }
+
+    /**
+     * Normalizes one of the following values:
+     * - lucene class (eg: org.apache.lucene.analysis.en.EnglishAnalyzer -> 
english)
+     * - lucene name (eg: Standard -> standard)
+     * into the elasticsearch compatible value
+     */
+    private static String normalize(String value) {
+        // this might be a full class, let's tokenize the value
+        String[] anlClassTokens = value.split("\\.");
+        // and take the last part
+        String name = anlClassTokens[anlClassTokens.length - 1];
+        // all options in elastic are in snake case
+        name = CaseFormat.UPPER_CAMEL.to(CaseFormat.LOWER_UNDERSCORE, name);
+        // if it ends with analyzer we need to get rid of it
+        if (name.endsWith("_analyzer")) {
+            name = name.replace("_analyzer", "");
+        }
+        return name;
+    }
+
+    private static Map<String, Object> convertNodeState(NodeState state) {
+        return convertNodeState(state, Collections.emptyMap());
+    }
+
+    private static Map<String, Object> convertNodeState(NodeState state, 
Map<String, String> mapping) {
+        return 
StreamSupport.stream(Spliterators.spliteratorUnknownSize(state.getProperties().iterator(),
 Spliterator.ORDERED), false)
+                .filter(ps -> ps.getType() != Type.BINARY)
+                .filter(ps -> !ps.isArray())
+                .filter(ps -> !NodeStateUtils.isHidden(ps.getName()))
+                .filter(ps -> !IGNORE_PROP_NAMES.contains(ps.getName()))

Review Comment:
   Nitpick: this could be transformed into a single filter and series of &&. It 
would generate less bytecode and be more efficient. In this case, it's not too 
important, but in general, I think it is as legible as having multiple chained 
filters, so there is not much to lose in grouping into a single filter.    



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