Github user mattyb149 commented on a diff in the pull request:
https://github.com/apache/nifi/pull/254#discussion_r71981046
--- Diff:
nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/ConvertJSONtoCSV.java
---
@@ -0,0 +1,360 @@
+/*
+ * 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 org.apache.commons.io.IOUtils;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.nifi.annotation.behavior.InputRequirement;
+import org.apache.nifi.annotation.behavior.WritesAttribute;
+import org.apache.nifi.annotation.documentation.CapabilityDescription;
+import org.apache.nifi.annotation.documentation.Tags;
+import org.apache.nifi.annotation.lifecycle.OnScheduled;
+import org.apache.nifi.components.AllowableValue;
+import org.apache.nifi.components.PropertyDescriptor;
+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 org.apache.nifi.processor.io.StreamCallback;
+import org.apache.nifi.processor.util.StandardValidators;
+import org.json.JSONArray;
+import org.json.JSONException;
+import org.json.JSONObject;
+import org.json.JSONTokener;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+import java.util.TreeSet;
+
+@Tags({"JSON, CSV, convert"})
+@InputRequirement(InputRequirement.Requirement.INPUT_REQUIRED)
+@WritesAttribute(attribute="mime.type", description="Sets the mime type to
application/csv")
+@CapabilityDescription("Converts a JSON document to CSV. This processor
reads the entire content " +
+ "of incoming FlowFiles into memory in order to perform the
conversion. The processor will parse JSON Arrays, JSON Objects " +
+ "and the combination of the two regardless of the level of nesting
in the JSON document.")
+public class ConvertJSONtoCSV extends AbstractProcessor {
+ volatile String delimiter;
+ volatile String removeFields;
+ volatile String emptyFields = "";
+
+ public static final AllowableValue INCLUDE_HEADER_TRUE = new
AllowableValue(
+ "True", "True", "Creates headers for each JSON file.");
+ public static final AllowableValue INCLUDE_HEADER_FALSE = new
AllowableValue(
+ "False", "False", "Only parses the JSON fields and does not
include headers");
+
+
+ public static final PropertyDescriptor DELIMITER = new
PropertyDescriptor
+ .Builder().name("CSV Delimiter")
+ .description("Delimiter used for the generated CSV output
(Example: , | -)")
+ .required(true)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor REMOVE_FIELDS = new
PropertyDescriptor
+ .Builder().name("Remove JSON Fields/Columns")
+ .description("Comma delimited list of columns that should be
removed when parsing JSON and building the CSV. " +
+ "This includes all top level and most granular nested
fields/columns. By default with nothing specified every field " +
+ "will be parsed.")
+ .required(false)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor EMPTY_FIELDS = new
PropertyDescriptor
+ .Builder().name("Empty field value")
+ .description("During denormalization/flattening of the JSON
the value that will be substituted for empty fields values " +
+ "(Example: NULL). Defaults to empty string if not
specified.")
+ .required(false)
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final PropertyDescriptor INCLUDE_HEADERS = new
PropertyDescriptor
+ .Builder().name("Include Headers")
+ .description("Whether or not to include headers in the CSV
output")
+ .required(true)
+ .allowableValues(INCLUDE_HEADER_TRUE, INCLUDE_HEADER_FALSE)
+ .defaultValue(INCLUDE_HEADER_TRUE.getValue())
+ .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
+ .build();
+
+ public static final Relationship RELATIONSHIP_SUCCESS = new
Relationship.Builder()
+ .name("success")
+ .description("Successfully parsing the JSON file to CSV ")
+ .build();
+
+ public static final Relationship RELATIONSHIP_FAILURE = new
Relationship.Builder()
+ .name("failure")
+ .description("Failed parsing the JSON file to CSV ")
+ .build();
+
+ private List<PropertyDescriptor> descriptors;
+
+ private Set<Relationship> relationships;
+
+ @Override
+ protected void init(final ProcessorInitializationContext context) {
+ final List<PropertyDescriptor> descriptors = new
ArrayList<PropertyDescriptor>();
+ descriptors.add(DELIMITER);
+ descriptors.add(REMOVE_FIELDS);
+ descriptors.add(EMPTY_FIELDS);
+ descriptors.add(INCLUDE_HEADERS);
+ this.descriptors = Collections.unmodifiableList(descriptors);
+
+ final Set<Relationship> relationships = new
HashSet<Relationship>();
+ relationships.add(RELATIONSHIP_SUCCESS);
+ relationships.add(RELATIONSHIP_FAILURE);
+ this.relationships = Collections.unmodifiableSet(relationships);
+ }
+
+ @Override
+ public Set<Relationship> getRelationships() {
+
+ return this.relationships;
+ }
+
+ @Override
+ public final List<PropertyDescriptor>
getSupportedPropertyDescriptors() {
+
+ return descriptors;
+ }
+
+ @OnScheduled
+ public void onScheduled(final ProcessContext context) {
+
+ delimiter = context.getProperty(DELIMITER).getValue();
+ removeFields = context.getProperty(REMOVE_FIELDS).getValue() ==
null ? "" : context.getProperty(REMOVE_FIELDS).getValue();
+ emptyFields = context.getProperty(EMPTY_FIELDS).getValue();
+ }
+
+ @Override
+ public void onTrigger(final ProcessContext context, final
ProcessSession session) throws ProcessException {
+ final String includeHeaders =
context.getProperty(INCLUDE_HEADERS).getValue();
+
+ FlowFile flowFile = session.get();
+ if ( flowFile == null ) {
+ return;
+ }
+
+ try {
+ flowFile = session.write(flowFile, new StreamCallback() {
+ @Override
+ public void process(final InputStream inputStream, final
OutputStream outputStream) throws IOException {
+ List<Map<String, String>> flatJson;
+ try {
+ flatJson =
JSONParser.parseJSON(IOUtils.toString(inputStream, "UTF-8"), getRemoveKeySet());
+ if (flatJson == null) {
+ throw new IOException("Unable to parse JSON
file. Please check the file contains valid JSON structure");
+ }
+ } catch (JSONException ex) {
+ throw new JSONException("Unable to parse as JSON
appears to be malformed: " + ex);
+ }
+ outputStream.write(CSVGenerator.generateCSV(flatJson,
delimiter, emptyFields, includeHeaders).toString().getBytes());
+ }
+ });
+
+ session.transfer(flowFile, RELATIONSHIP_SUCCESS);
+ } catch (ProcessException | JSONException ex) {
+ getLogger().error("Error converting FlowFile to CSV due to
{}", new Object[] {ex.getMessage()}, ex);
+ session.transfer(flowFile, RELATIONSHIP_FAILURE);
+ }
+
+ }
+
+ private Set<String> getRemoveKeySet() {
+ Set<String> setRemove = new HashSet<>();
+
+ final String[] fields = removeFields.split(",");
+ for (String field : fields) {
+ setRemove.add(field);
+ }
+ return setRemove;
+ }
+
+ private static class JSONParser {
+
+ private static final Class<?> JSON_OBJECT = JSONObject.class;
+
+ private static final Class<?> JSON_ARRAY = JSONArray.class;
+
+ private static Set<String> removeKeySet = new HashSet<>();
+
+ public static List<Map<String, String>> parseJSON(String json,
Set<String> removeKeys) throws JSONException {
+ List<Map<String, String>> flatJson = null;
+ removeKeySet = removeKeys;
+
+ // we don't know if we are dealing with a JSON object or an
array
+ // not handling this properly causes un-necessary exception to
be thrown
+ // instantiate to a generic object and check what we are
dealing with
+ Object objJSON = new JSONTokener(json).nextValue();
+
+ try {
+ if (objJSON instanceof JSONObject) {
+ JSONObject jsonObject = new JSONObject(json);
+ flatJson = new ArrayList<Map<String, String>>();
+ flatJson.add(parse(jsonObject));
+ } else if (objJSON instanceof JSONArray) {
+ flatJson = handleAsArray(json);
+ }
+ } catch (JSONException ex) {
+ throw new JSONException("JSON might be malformed, please
check and make sure it is valid JSON format: " + ex);
+ }
+
+ return flatJson;
+ }
+
+ public static Map<String, String> parse(JSONObject jsonObject) {
+ Map<String, String> flatJson = new LinkedHashMap<String,
String>();
+ try {
+ denormalize(jsonObject, flatJson, "");
+ } catch (Exception ex) {
+ throw ex;
+ }
+ return flatJson;
+ }
+
+ public static List<Map<String, String>> parse(JSONArray jsonArray)
{
+ JSONObject jsonObject = null;
+ List<Map<String, String>> flatJson = new ArrayList<Map<String,
String>>();
+ int length = jsonArray.length();
+
+ for (int i = 0; i < length; i++) {
+ jsonObject = jsonArray.getJSONObject(i);
+ Map<String, String> stringMap = parse(jsonObject);
+ flatJson.add(stringMap);
+ }
+
+ return flatJson;
+ }
+
+ private static List<Map<String, String>> handleAsArray(String
json) throws JSONException {
+ List<Map<String, String>> flatJson = null;
+
+ try {
+ JSONArray jsonArray = new JSONArray(json);
+ flatJson = parse(jsonArray);
--- End diff --
Can this be parallelized somehow? Fork/Join or whatever? Not sure about
overhead, just asking :)
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