| 1 | /* |
| 2 | * Copyright 2006-2007 the original author or authors. |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | package org.springframework.batch.core.scope.context; |
| 17 | |
| 18 | import java.util.Queue; |
| 19 | import java.util.concurrent.LinkedBlockingQueue; |
| 20 | |
| 21 | import org.apache.commons.logging.Log; |
| 22 | import org.apache.commons.logging.LogFactory; |
| 23 | import org.springframework.batch.core.Step; |
| 24 | import org.springframework.batch.core.StepExecution; |
| 25 | import org.springframework.batch.repeat.RepeatCallback; |
| 26 | import org.springframework.batch.repeat.RepeatContext; |
| 27 | import org.springframework.batch.repeat.RepeatStatus; |
| 28 | import org.springframework.util.ObjectUtils; |
| 29 | |
| 30 | /** |
| 31 | * Convenient base class for clients who need to do something in a repeat |
| 32 | * callback inside a {@link Step}. |
| 33 | * |
| 34 | * @author Dave Syer |
| 35 | * |
| 36 | */ |
| 37 | public abstract class StepContextRepeatCallback implements RepeatCallback { |
| 38 | |
| 39 | private final Queue<ChunkContext> attributeQueue = new LinkedBlockingQueue<ChunkContext>(); |
| 40 | |
| 41 | private final StepExecution stepExecution; |
| 42 | |
| 43 | private final Log logger = LogFactory.getLog(StepContextRepeatCallback.class); |
| 44 | |
| 45 | /** |
| 46 | * @param stepExecution |
| 47 | */ |
| 48 | public StepContextRepeatCallback(StepExecution stepExecution) { |
| 49 | this.stepExecution = stepExecution; |
| 50 | } |
| 51 | |
| 52 | /** |
| 53 | * Manage the {@link StepContext} lifecycle. Business processing should be |
| 54 | * delegated to {@link #doInChunkContext(RepeatContext, ChunkContext)}. This |
| 55 | * is to ensure that the current thread has a reference to the context, even |
| 56 | * if the callback is executed in a pooled thread. Handles the registration |
| 57 | * and de-registration of the step context, so clients should not duplicate |
| 58 | * those calls. |
| 59 | * |
| 60 | * @see RepeatCallback#doInIteration(RepeatContext) |
| 61 | */ |
| 62 | public RepeatStatus doInIteration(RepeatContext context) throws Exception { |
| 63 | |
| 64 | // The StepContext has to be the same for all chunks, |
| 65 | // otherwise step-scoped beans will be re-initialised for each chunk. |
| 66 | StepContext stepContext = StepSynchronizationManager.register(stepExecution); |
| 67 | logger.debug("Preparing chunk execution for StepContext: "+ObjectUtils.identityToString(stepContext)); |
| 68 | |
| 69 | ChunkContext chunkContext = attributeQueue.poll(); |
| 70 | if (chunkContext == null) { |
| 71 | chunkContext = new ChunkContext(stepContext); |
| 72 | } |
| 73 | |
| 74 | try { |
| 75 | logger.debug("Chunk execution starting: queue size="+attributeQueue.size()); |
| 76 | return doInChunkContext(context, chunkContext); |
| 77 | } |
| 78 | finally { |
| 79 | // Still some stuff to do with the data in this chunk, |
| 80 | // pass it back. |
| 81 | if (!chunkContext.isComplete()) { |
| 82 | attributeQueue.add(chunkContext); |
| 83 | } |
| 84 | StepSynchronizationManager.close(); |
| 85 | } |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Do the work required for this chunk of the step. The {@link ChunkContext} |
| 90 | * provided is managed by the base class, so that if there is still work to |
| 91 | * do for the task in hand state can be stored here. In a multi-threaded |
| 92 | * client, the base class ensures that only one thread at a time can be |
| 93 | * working on each instance of {@link ChunkContext}. Workers should signal |
| 94 | * that they are finished with a context by removing all the attributes they |
| 95 | * have added. If a worker does not remove them another thread might see |
| 96 | * stale state. |
| 97 | * |
| 98 | * @param context the current {@link RepeatContext} |
| 99 | * @param chunkContext the chunk context in which to carry out the work |
| 100 | * @return the repeat status from the execution |
| 101 | * @throws Exception implementations can throw an exception if anything goes |
| 102 | * wrong |
| 103 | */ |
| 104 | public abstract RepeatStatus doInChunkContext(RepeatContext context, ChunkContext chunkContext) throws Exception; |
| 105 | |
| 106 | } |