| 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 | |
| 17 | package org.springframework.batch.core.step.item; |
| 18 | |
| 19 | import java.util.List; |
| 20 | |
| 21 | import org.apache.commons.logging.Log; |
| 22 | import org.apache.commons.logging.LogFactory; |
| 23 | import org.springframework.batch.core.StepContribution; |
| 24 | import org.springframework.batch.core.StepListener; |
| 25 | import org.springframework.batch.core.listener.MulticasterBatchListener; |
| 26 | import org.springframework.batch.item.ItemReader; |
| 27 | import org.springframework.batch.repeat.RepeatCallback; |
| 28 | import org.springframework.batch.repeat.RepeatContext; |
| 29 | import org.springframework.batch.repeat.RepeatOperations; |
| 30 | import org.springframework.batch.repeat.RepeatStatus; |
| 31 | |
| 32 | /** |
| 33 | * Simple implementation of the ChunkProvider interface that does basic chunk |
| 34 | * providing from an {@link ItemReader}. |
| 35 | * |
| 36 | * @author Dave Syer |
| 37 | * @see ChunkOrientedTasklet |
| 38 | */ |
| 39 | public class SimpleChunkProvider<I> implements ChunkProvider<I> { |
| 40 | |
| 41 | protected final Log logger = LogFactory.getLog(getClass()); |
| 42 | |
| 43 | protected final ItemReader<? extends I> itemReader; |
| 44 | |
| 45 | private final MulticasterBatchListener<I, ?> listener = new MulticasterBatchListener<I, Object>(); |
| 46 | |
| 47 | private final RepeatOperations repeatOperations; |
| 48 | |
| 49 | public SimpleChunkProvider(ItemReader<? extends I> itemReader, RepeatOperations repeatOperations) { |
| 50 | this.itemReader = itemReader; |
| 51 | this.repeatOperations = repeatOperations; |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * Register some {@link StepListener}s with the handler. Each will get the |
| 56 | * callbacks in the order specified at the correct stage. |
| 57 | * |
| 58 | * @param listeners |
| 59 | */ |
| 60 | public void setListeners(List<? extends StepListener> listeners) { |
| 61 | for (StepListener listener : listeners) { |
| 62 | registerListener(listener); |
| 63 | } |
| 64 | } |
| 65 | |
| 66 | /** |
| 67 | * Register a listener for callbacks at the appropriate stages in a process. |
| 68 | * |
| 69 | * @param listener a {@link StepListener} |
| 70 | */ |
| 71 | public void registerListener(StepListener listener) { |
| 72 | this.listener.register(listener); |
| 73 | } |
| 74 | |
| 75 | /** |
| 76 | * @return the listener |
| 77 | */ |
| 78 | protected MulticasterBatchListener<I, ?> getListener() { |
| 79 | return listener; |
| 80 | } |
| 81 | |
| 82 | /** |
| 83 | * Surrounds the read call with listener callbacks. |
| 84 | * @return item |
| 85 | * @throws Exception |
| 86 | */ |
| 87 | protected final I doRead() throws Exception { |
| 88 | try { |
| 89 | listener.beforeRead(); |
| 90 | I item = itemReader.read(); |
| 91 | if(item != null) { |
| 92 | listener.afterRead(item); |
| 93 | } |
| 94 | return item; |
| 95 | } |
| 96 | catch (Exception e) { |
| 97 | listener.onReadError(e); |
| 98 | throw e; |
| 99 | } |
| 100 | } |
| 101 | |
| 102 | public Chunk<I> provide(final StepContribution contribution) throws Exception { |
| 103 | |
| 104 | final Chunk<I> inputs = new Chunk<I>(); |
| 105 | repeatOperations.iterate(new RepeatCallback() { |
| 106 | |
| 107 | public RepeatStatus doInIteration(final RepeatContext context) throws Exception { |
| 108 | I item = null; |
| 109 | try { |
| 110 | item = read(contribution, inputs); |
| 111 | } |
| 112 | catch (SkipOverflowException e) { |
| 113 | // read() tells us about an excess of skips by throwing an |
| 114 | // exception |
| 115 | return RepeatStatus.FINISHED; |
| 116 | } |
| 117 | if (item == null) { |
| 118 | inputs.setEnd(); |
| 119 | return RepeatStatus.FINISHED; |
| 120 | } |
| 121 | inputs.add(item); |
| 122 | contribution.incrementReadCount(); |
| 123 | return RepeatStatus.CONTINUABLE; |
| 124 | } |
| 125 | |
| 126 | }); |
| 127 | |
| 128 | return inputs; |
| 129 | |
| 130 | } |
| 131 | |
| 132 | public void postProcess(StepContribution contribution, Chunk<I> chunk) { |
| 133 | // do nothing |
| 134 | } |
| 135 | |
| 136 | /** |
| 137 | * Delegates to {@link #doRead()}. Subclasses can add additional behaviour |
| 138 | * (e.g. exception handling). |
| 139 | * |
| 140 | * @param contribution the current step execution contribution |
| 141 | * @param chunk the current chunk |
| 142 | * @return a new item for processing |
| 143 | * |
| 144 | * @throws SkipOverflowException if specifically the chunk is accumulating |
| 145 | * too much data (e.g. skips) and it wants to force a commit. |
| 146 | * |
| 147 | * @throws Exception if there is a generic issue |
| 148 | */ |
| 149 | protected I read(StepContribution contribution, Chunk<I> chunk) throws SkipOverflowException, Exception { |
| 150 | return doRead(); |
| 151 | } |
| 152 | |
| 153 | } |