Github user mattyb149 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/2307#discussion_r154498488
--- 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);
--- End diff --
All of the processors I checked that have an "original" relationship will
only output the original flow file on successful transformation (i.e. not
transferred to failure), and usually only when an incoming flow file can
generate multiple output flow files. Are you sure you need/want an "original"
relationship? Perhaps instead you can just overwrite the incoming flow file,
sending the changed contents to success, or the original to failure depending
on the outcome of the operation. If you do want an "original", I recommend only
sending the flow file to original if successful, as the original flow file's
contents will be the contents of the one on the "failure" relationship, right?
---
