Github user mattyb149 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2307#discussion_r154498501
--- Diff:
nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/FlattenJson.java
---
@@ -0,0 +1,134 @@
+/*
+ * 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.nifi.processors.standard;
+
+import com.github.wnameless.json.flattener.FlattenMode;
+import com.github.wnameless.json.flattener.JsonFlattener;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.components.PropertyDescriptor;
+import org.apache.nifi.components.ValidationResult;
+import org.apache.nifi.flowfile.FlowFile;
+import org.apache.nifi.processor.AbstractProcessor;
+import org.apache.nifi.processor.ProcessContext;
+import org.apache.nifi.processor.ProcessSession;
+import org.apache.nifi.processor.ProcessorInitializationContext;
+import org.apache.nifi.processor.Relationship;
+import org.apache.nifi.processor.exception.ProcessException;
+
+import java.io.ByteArrayOutputStream;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+@Tags({ "json", "flatten" })
+@CapabilityDescription(
+ "Provides the user with the ability to take a nested JSON document
and flatten it into a simple key/value pair " +
+ "document. The keys are combined at each level with a user-defined
separator that defaults to '.'"
+)
+public class FlattenJson extends AbstractProcessor {
+ static final Relationship REL_SUCCESS = new Relationship.Builder()
+ .description("Successfully flattened files go to this
relationship.")
+ .name("success")
+ .build();
+ static final Relationship REL_FAILURE = new Relationship.Builder()
+ .description("Files that cannot be flattened go to this
relationship.")
+ .name("failure")
+ .build();
+ static final Relationship REL_ORIGINAL = new Relationship.Builder()
+ .description("The original files are copied to this
relationship; autoterminated by default.")
+ .autoTerminateDefault(true)
+ .name("original")
+ .build();
+
+ static final PropertyDescriptor SEPARATOR = new
PropertyDescriptor.Builder()
+ .name("flatten-json-separator")
+ .displayName("Separator")
+ .defaultValue(".")
+ .description("The separator character used for joining keys.
Must be a JSON-legal character.")
+ .addValidator((subject, input, context) -> {
+ boolean valid = input != null && input.length() == 1;
+ String message = !valid ? "The separator must be a single
character in length." : "";
+
+ return new
ValidationResult.Builder().subject(subject).input(input).valid(valid).explanation(message).build();
+ })
+ .expressionLanguageSupported(true)
+ .build();
+
+ private List<PropertyDescriptor> properties;
+ private Set<Relationship> relationships;
+
+ @Override
+ protected void init(final ProcessorInitializationContext context) {
+ List<PropertyDescriptor> props = new ArrayList<>();
+ props.add(SEPARATOR);
+ properties = Collections.unmodifiableList(props);
+
+ Set<Relationship> rels = new HashSet<>();
+ rels.add(REL_SUCCESS);
+ rels.add(REL_FAILURE);
+ rels.add(REL_ORIGINAL);
+
+ relationships = Collections.unmodifiableSet(rels);
+ }
+
+ @Override
+ protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
+ return properties;
+ }
+
+ @Override
+ public Set<Relationship> getRelationships() {
+ return relationships;
+ }
+
+ @Override
+ public void onTrigger(final ProcessContext context, final
ProcessSession session) throws ProcessException {
+ FlowFile flowFile = session.get();
+ if (flowFile == null) {
+ return;
+ }
+
+ FlowFile cloned = session.clone(flowFile);
+ String separator =
context.getProperty(SEPARATOR).evaluateAttributeExpressions(flowFile).getValue();
+
+ try {
+ ByteArrayOutputStream bos = new ByteArrayOutputStream();
+ session.exportTo(flowFile, bos);
+ bos.close();
+
+ String raw = new String(bos.toByteArray());
+ final String flattened = new JsonFlattener(raw)
+ .withFlattenMode(FlattenMode.KEEP_ARRAYS)
+ .withSeparator(separator.charAt(0))
+ .flatten();
+
+ flowFile = session.write(flowFile, os ->
os.write(flattened.getBytes()));
+
+ session.transfer(flowFile, REL_SUCCESS);
+ } catch (Exception ex) {
+ session.transfer(flowFile, REL_FAILURE);
+ } finally {
+ session.transfer(cloned, REL_ORIGINAL);
+ }
+
+ session.commit();
--- End diff --
When subclassing from AbstractProcessor, you don't need the commit here,
AbstractProcessor will call it for you after your onTrigger() returns.
---
