001/* 002 * Copyright 2006-2018 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016package org.springframework.batch.core.scope.context; 017 018import java.util.Queue; 019import java.util.concurrent.LinkedBlockingQueue; 020 021import org.apache.commons.logging.Log; 022import org.apache.commons.logging.LogFactory; 023import org.springframework.batch.core.Step; 024import org.springframework.batch.core.StepExecution; 025import org.springframework.batch.repeat.RepeatCallback; 026import org.springframework.batch.repeat.RepeatContext; 027import org.springframework.batch.repeat.RepeatStatus; 028import org.springframework.util.ObjectUtils; 029 030/** 031 * Convenient base class for clients who need to do something in a repeat 032 * callback inside a {@link Step}. 033 * 034 * @author Dave Syer 035 * @author Mahmoud Ben Hassine 036 * 037 */ 038public abstract class StepContextRepeatCallback implements RepeatCallback { 039 040 private final Queue<ChunkContext> attributeQueue = new LinkedBlockingQueue<ChunkContext>(); 041 042 private final StepExecution stepExecution; 043 044 private final Log logger = LogFactory.getLog(StepContextRepeatCallback.class); 045 046 /** 047 * @param stepExecution instance of {@link StepExecution} to be used by StepContextRepeatCallback. 048 */ 049 public StepContextRepeatCallback(StepExecution stepExecution) { 050 this.stepExecution = stepExecution; 051 } 052 053 /** 054 * Manage the {@link StepContext} lifecycle. Business processing should be 055 * delegated to {@link #doInChunkContext(RepeatContext, ChunkContext)}. This 056 * is to ensure that the current thread has a reference to the context, even 057 * if the callback is executed in a pooled thread. Handles the registration 058 * and unregistration of the step context, so clients should not duplicate 059 * those calls. 060 * 061 * @see RepeatCallback#doInIteration(RepeatContext) 062 */ 063 @Override 064 public RepeatStatus doInIteration(RepeatContext context) throws Exception { 065 066 // The StepContext has to be the same for all chunks, 067 // otherwise step-scoped beans will be re-initialised for each chunk. 068 StepContext stepContext = StepSynchronizationManager.register(stepExecution); 069 if (logger.isDebugEnabled()) { 070 logger.debug("Preparing chunk execution for StepContext: "+ObjectUtils.identityToString(stepContext)); 071 } 072 073 ChunkContext chunkContext = attributeQueue.poll(); 074 if (chunkContext == null) { 075 chunkContext = new ChunkContext(stepContext); 076 } 077 078 try { 079 if (logger.isDebugEnabled()) { 080 logger.debug("Chunk execution starting: queue size="+attributeQueue.size()); 081 } 082 return doInChunkContext(context, chunkContext); 083 } 084 finally { 085 // Still some stuff to do with the data in this chunk, 086 // pass it back. 087 if (!chunkContext.isComplete()) { 088 attributeQueue.add(chunkContext); 089 } 090 StepSynchronizationManager.close(); 091 } 092 } 093 094 /** 095 * Do the work required for this chunk of the step. The {@link ChunkContext} 096 * provided is managed by the base class, so that if there is still work to 097 * do for the task in hand state can be stored here. In a multi-threaded 098 * client, the base class ensures that only one thread at a time can be 099 * working on each instance of {@link ChunkContext}. Workers should signal 100 * that they are finished with a context by removing all the attributes they 101 * have added. If a worker does not remove them another thread might see 102 * stale state. 103 * 104 * @param context the current {@link RepeatContext} 105 * @param chunkContext the chunk context in which to carry out the work 106 * @return the repeat status from the execution 107 * @throws Exception implementations can throw an exception if anything goes 108 * wrong 109 */ 110 public abstract RepeatStatus doInChunkContext(RepeatContext context, ChunkContext chunkContext) throws Exception; 111 112}