Java tutorial
/* * 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.msgpack; import java.io.*; import java.util.List; import java.util.ArrayList; import java.util.Set; import java.util.HashSet; import java.util.Collections; import java.io.InputStream; import java.io.OutputStream; import java.io.BufferedOutputStream; import java.io.IOException; import java.nio.charset.StandardCharsets; import java.util.concurrent.atomic.AtomicBoolean; import org.apache.commons.io.IOUtils; import com.fasterxml.jackson.databind.ObjectMapper; import com.fasterxml.jackson.databind.JsonNode; import com.fasterxml.jackson.core.JsonProcessingException; import org.msgpack.jackson.dataformat.MessagePackFactory; import org.msgpack.jackson.dataformat.JsonArrayFormat; import org.apache.nifi.components.PropertyDescriptor; import org.apache.nifi.components.PropertyValue; import org.apache.nifi.flowfile.FlowFile; import org.apache.nifi.flowfile.attributes.CoreAttributes; import org.apache.nifi.processor.*; import org.apache.nifi.annotation.behavior.ReadsAttribute; import org.apache.nifi.annotation.behavior.ReadsAttributes; import org.apache.nifi.annotation.behavior.WritesAttribute; import org.apache.nifi.annotation.behavior.WritesAttributes; import org.apache.nifi.annotation.lifecycle.OnScheduled; import org.apache.nifi.annotation.documentation.CapabilityDescription; import org.apache.nifi.annotation.documentation.SeeAlso; import org.apache.nifi.annotation.documentation.Tags; import org.apache.nifi.processor.exception.ProcessException; import org.apache.nifi.processor.util.StandardValidators; import org.apache.nifi.processor.io.StreamCallback; @Tags({ "msgpack", "messagepack", "json", "serialization" }) @CapabilityDescription("Serialize JSON in MessagePack format") @SeeAlso({}) @ReadsAttribute(attribute = "mime.type", description = "If the input format is set to use mime.type attribute, " + "this attribute is used to determine the input type. Otherwise, this " + "attribute is ignored.") @WritesAttribute(attribute = "mime.type", description = "If the FlowFile is successfully converted, the MIME type " + "will be updated to application/msgpack") public class MessagePackPack extends AbstractProcessor { private static final String USE_MIME_TYPE = "use mime.type attribute"; private static final String JSON = "JSON"; private static final String XML = "XML"; private static final String MIME_TYPE = "application/msgpack"; private static final String MIME_EXT = ".msgpack"; private static final String MIME_EXT_KEY = "mime.extension"; public static final PropertyDescriptor INPUT_FORMAT = new PropertyDescriptor.Builder().name("input-format") .displayName("Input Format").description("").required(true).defaultValue(USE_MIME_TYPE) .allowableValues(USE_MIME_TYPE, JSON, XML).addValidator(StandardValidators.NON_EMPTY_VALIDATOR).build(); public static final Relationship REL_SUCCESS = new Relationship.Builder().name("success") .description("Any FlowFile that is successfully converted is routed to " + "this relationship").build(); public static final Relationship REL_FAILURE = new Relationship.Builder().name("failure") .description("Any FlowFile that fails to be converted is routed to " + "this relationship").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(INPUT_FORMAT); this.descriptors = Collections.unmodifiableList(descriptors); final Set<Relationship> relationships = new HashSet<Relationship>(); relationships.add(REL_SUCCESS); relationships.add(REL_FAILURE); this.relationships = Collections.unmodifiableSet(relationships); } @Override public Set<Relationship> getRelationships() { return relationships; } @Override public final List<PropertyDescriptor> getSupportedPropertyDescriptors() { return descriptors; } @OnScheduled public void onScheduled(final ProcessContext context) { } @Override public void onTrigger(final ProcessContext context, final ProcessSession session) throws ProcessException { FlowFile flowFile = session.get(); if (flowFile == null) { return; } final ObjectMapper reader = new ObjectMapper(); final ObjectMapper writer = new ObjectMapper(new MessagePackFactory()); writer.setAnnotationIntrospector(new JsonArrayFormat()); final AtomicBoolean failed = new AtomicBoolean(false); flowFile = session.write(flowFile, new StreamCallback() { @Override public void process(InputStream is, OutputStream os) throws IOException { try (final OutputStream msgpack = new BufferedOutputStream(os)) { final JsonNode json = reader.readTree(is); final byte[] bytes = writer.writeValueAsBytes(json); msgpack.write(bytes); msgpack.flush(); } catch (JsonProcessingException e) { getLogger().error(e.getMessage(), e); failed.set(true); } } }); if (failed.get()) { session.transfer(flowFile, REL_FAILURE); return; } flowFile = session.putAttribute(flowFile, CoreAttributes.MIME_TYPE.key(), MIME_TYPE); flowFile = session.putAttribute(flowFile, MIME_EXT_KEY, MIME_EXT); session.transfer(flowFile, REL_SUCCESS); } }