| 1 | /* |
| 2 | * Copyright 2006-2009 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 | |
| 17 | package org.springframework.batch.core.step.item; |
| 18 | |
| 19 | import org.apache.commons.logging.Log; |
| 20 | import org.apache.commons.logging.LogFactory; |
| 21 | import org.springframework.batch.core.StepContribution; |
| 22 | import org.springframework.batch.core.scope.context.ChunkContext; |
| 23 | import org.springframework.batch.core.step.tasklet.Tasklet; |
| 24 | import org.springframework.batch.repeat.RepeatStatus; |
| 25 | |
| 26 | /** |
| 27 | * A {@link Tasklet} implementing variations on read-process-write item |
| 28 | * handling. |
| 29 | * |
| 30 | * @author Dave Syer |
| 31 | * |
| 32 | * @param <I> input item type |
| 33 | */ |
| 34 | public class ChunkOrientedTasklet<I> implements Tasklet { |
| 35 | |
| 36 | private static final String INPUTS_KEY = "INPUTS"; |
| 37 | |
| 38 | private final ChunkProcessor<I> chunkProcessor; |
| 39 | |
| 40 | private final ChunkProvider<I> chunkProvider; |
| 41 | |
| 42 | private boolean buffering = true; |
| 43 | |
| 44 | private static Log logger = LogFactory.getLog(ChunkOrientedTasklet.class); |
| 45 | |
| 46 | public ChunkOrientedTasklet(ChunkProvider<I> chunkProvider, ChunkProcessor<I> chunkProcessor) { |
| 47 | this.chunkProvider = chunkProvider; |
| 48 | this.chunkProcessor = chunkProcessor; |
| 49 | } |
| 50 | |
| 51 | /** |
| 52 | * Flag to indicate that items should be buffered once read. Defaults to |
| 53 | * true, which is appropriate for forward-only, non-transactional item |
| 54 | * readers. Main (or only) use case for setting this flag to false is a |
| 55 | * transactional JMS item reader. |
| 56 | * |
| 57 | * @param buffering |
| 58 | */ |
| 59 | public void setBuffering(boolean buffering) { |
| 60 | this.buffering = buffering; |
| 61 | } |
| 62 | |
| 63 | public RepeatStatus execute(StepContribution contribution, ChunkContext chunkContext) throws Exception { |
| 64 | |
| 65 | @SuppressWarnings("unchecked") |
| 66 | Chunk<I> inputs = (Chunk<I>) chunkContext.getAttribute(INPUTS_KEY); |
| 67 | if (inputs == null) { |
| 68 | inputs = chunkProvider.provide(contribution); |
| 69 | if (buffering) { |
| 70 | chunkContext.setAttribute(INPUTS_KEY, inputs); |
| 71 | } |
| 72 | } |
| 73 | |
| 74 | chunkProcessor.process(contribution, inputs); |
| 75 | chunkProvider.postProcess(contribution, inputs); |
| 76 | |
| 77 | // Allow a message coming back from the processor to say that we |
| 78 | // are not done yet |
| 79 | if (inputs.isBusy()) { |
| 80 | logger.debug("Inputs still busy"); |
| 81 | return RepeatStatus.CONTINUABLE; |
| 82 | } |
| 83 | |
| 84 | chunkContext.removeAttribute(INPUTS_KEY); |
| 85 | chunkContext.setComplete(); |
| 86 | |
| 87 | logger.debug("Inputs not busy, ended: " + inputs.isEnd()); |
| 88 | return RepeatStatus.continueIf(!inputs.isEnd()); |
| 89 | |
| 90 | } |
| 91 | |
| 92 | } |