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 it.ecubecenter.processors.zookeeper; import com.fasterxml.jackson.databind.ObjectMapper; import it.ecubecenter.processors.zookeeper.utils.ThreadsafeZookeeperClient; import org.apache.nifi.annotation.behavior.WritesAttribute; 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.annotation.lifecycle.OnScheduled; import org.apache.nifi.components.PropertyDescriptor; import org.apache.nifi.flowfile.FlowFile; import org.apache.nifi.flowfile.attributes.CoreAttributes; import org.apache.nifi.processor.*; import org.apache.nifi.processor.exception.ProcessException; import org.apache.nifi.processor.io.OutputStreamCallback; import org.apache.nifi.processor.util.StandardValidators; import org.apache.nifi.stream.io.BufferedOutputStream; import java.io.IOException; import java.io.InvalidClassException; import java.io.OutputStream; import java.util.*; @Tags({ "zookeeper", "list", "znode" }) @CapabilityDescription("The processor lists the content of the provided zNode and returns the list of the children in the content of the FlowFile.") @SeeAlso({ ZookeeperWriter.class, ZookeeperDelete.class, ZookeeperReader.class }) @WritesAttribute(attribute = ZookeeperList.ATTIRUBTE_NAME, description = "The attribute in which the result is stored if the chosen destination is " + ZookeeperList.DESTINATION_CONTENT) public class ZookeeperList extends AbstractZookeeperProcessor { public static final String DESTINATION_ATTRIBUTE = "flowfile-attribute"; public static final String DESTINATION_CONTENT = "flowfile-content"; public static final String ATTIRUBTE_NAME = "zookeeper.list"; private static final ObjectMapper objMapper = new ObjectMapper(); private static Map<String, String> MIME_TYPE_MAP; static { MIME_TYPE_MAP = new HashMap<String, String>(); MIME_TYPE_MAP.put("csv", "application/csv"); MIME_TYPE_MAP.put("json", "application/json"); } public static final PropertyDescriptor ZNODE_NAME = new PropertyDescriptor.Builder().name("ZNode") .description("The ZNode to be listed").required(true).expressionLanguageSupported(true) .addValidator(StandardValidators.NON_EMPTY_VALIDATOR).build(); public static final PropertyDescriptor DESTINATION = new PropertyDescriptor.Builder().name("Destination") .description("Control if value is written as a new flowfile attribute '" + ATTIRUBTE_NAME + "' " + "or written in the flowfile content. Writing to flowfile content will overwrite any " + "existing flowfile content.") .required(true).allowableValues(DESTINATION_ATTRIBUTE, DESTINATION_CONTENT) .addValidator(StandardValidators.NON_EMPTY_VALIDATOR).build(); public static final PropertyDescriptor OUTPUT_FORMAT = new PropertyDescriptor.Builder().name("Output format") .description("The format of the output of the operation.").required(true).allowableValues("csv", "json") .addValidator(StandardValidators.NON_EMPTY_VALIDATOR).build(); public static final Relationship SUCCESS = new Relationship.Builder().name("success") .description("Success relationship").build(); public static final Relationship ZNODE_NOT_FOUND = new Relationship.Builder().name("znode_not_found") .description("When the ZNode does not exists the flow file is routed via this relationship.").build(); public static final Relationship FAILURE = new Relationship.Builder().name("failure") .description("Failure relationship").build(); private Set<Relationship> relationships; @Override protected void init(final ProcessorInitializationContext context) { super.init(context); final List<PropertyDescriptor> descriptors = new ArrayList<PropertyDescriptor>(); descriptors.add(ZNODE_NAME); descriptors.add(OUTPUT_FORMAT); descriptors.add(DESTINATION); descriptors.addAll(properties); this.properties = Collections.unmodifiableList(descriptors); final Set<Relationship> relationships = new HashSet<Relationship>(); relationships.add(SUCCESS); relationships.add(ZNODE_NOT_FOUND); relationships.add(FAILURE); this.relationships = Collections.unmodifiableSet(relationships); } @Override public Set<Relationship> getRelationships() { return this.relationships; } @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 String outputFormat = context.getProperty(OUTPUT_FORMAT).getValue(); renewKerberosAuthenticationIfNeeded(context); String zookeeperURL = context.getProperty(ZOOKEEPER_URL).getValue(); ThreadsafeZookeeperClient conn = ThreadsafeZookeeperClient.getConnection(zookeeperURL); int trials = 3; while (trials > 0) { try { String zNode = context.getProperty(ZNODE_NAME).evaluateAttributeExpressions(flowFile).getValue(); List<String> list = conn.listZNode(zNode); if (list == null) { session.getProvenanceReporter().route(flowFile, ZNODE_NOT_FOUND); session.transfer(flowFile, ZNODE_NOT_FOUND); } else { switch (context.getProperty(DESTINATION).getValue()) { case DESTINATION_CONTENT: flowFile = session.write(flowFile, new OutputStreamCallback() { @Override public void process(OutputStream outputStream) throws IOException { switch (outputFormat) { case "csv": StringBuilder sb = new StringBuilder(); boolean firstLine = true; for (String zNode : list) { if (!firstLine) { sb.append(System.lineSeparator()); } sb.append(zNode); firstLine = false; } outputStream.write(sb.toString().getBytes()); break; case "json": outputStream.write(objMapper.writeValueAsBytes(list)); break; default: throw new InvalidClassException("Unrecognized output format."); } } }); session.getProvenanceReporter().fetch(flowFile, zookeeperURL + zNode); flowFile = session.putAttribute(flowFile, CoreAttributes.MIME_TYPE.key(), MIME_TYPE_MAP.get(outputFormat)); break; case DESTINATION_ATTRIBUTE: switch (outputFormat) { case "csv": StringBuilder sb = new StringBuilder(); boolean firstLine = true; for (String zN : list) { if (!firstLine) { sb.append(","); } sb.append(zN); firstLine = false; } flowFile = session.putAttribute(flowFile, ATTIRUBTE_NAME, sb.toString()); break; case "json": flowFile = session.putAttribute(flowFile, ATTIRUBTE_NAME, objMapper.writeValueAsString(list)); break; default: throw new InvalidClassException("Unrecognized output format."); } session.getProvenanceReporter().modifyAttributes(flowFile); break; default: throw new InvalidClassException("Unrecognized destination."); } session.transfer(flowFile, SUCCESS); } break; } catch (Exception e) { try { conn.close(); } catch (InterruptedException e1) { getLogger().warn("Unable to close connection to Zookeeper.", e); } getLogger().warn("Error while listing from Zookeeper", e); } trials--; } if (trials == 0) { getLogger().error("Zookeeper operation failed 3 times"); session.transfer(flowFile, FAILURE); } } }