| 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.item.file; |
| 18 | |
| 19 | import java.util.Arrays; |
| 20 | import java.util.Comparator; |
| 21 | |
| 22 | import org.apache.commons.logging.Log; |
| 23 | import org.apache.commons.logging.LogFactory; |
| 24 | import org.springframework.batch.item.ExecutionContext; |
| 25 | import org.springframework.batch.item.ItemReader; |
| 26 | import org.springframework.batch.item.ItemStream; |
| 27 | import org.springframework.batch.item.ItemStreamException; |
| 28 | import org.springframework.batch.item.ParseException; |
| 29 | import org.springframework.batch.item.UnexpectedInputException; |
| 30 | import org.springframework.batch.item.util.ExecutionContextUserSupport; |
| 31 | import org.springframework.core.io.Resource; |
| 32 | import org.springframework.util.Assert; |
| 33 | import org.springframework.util.ClassUtils; |
| 34 | |
| 35 | /** |
| 36 | * Reads items from multiple resources sequentially - resource list is given by {@link #setResources(Resource[])}, the |
| 37 | * actual reading is delegated to {@link #setDelegate(ResourceAwareItemReaderItemStream)}. |
| 38 | * |
| 39 | * Input resources are ordered using {@link #setComparator(Comparator)} to make sure resource ordering is preserved |
| 40 | * between job runs in restart scenario. |
| 41 | * |
| 42 | * |
| 43 | * @author Robert Kasanicky |
| 44 | * @author Lucas Ward |
| 45 | */ |
| 46 | public class MultiResourceItemReader<T> implements ItemReader<T>, ItemStream { |
| 47 | |
| 48 | private static final Log logger = LogFactory.getLog(MultiResourceItemReader.class); |
| 49 | |
| 50 | private static final String RESOURCE_KEY = "resourceIndex"; |
| 51 | |
| 52 | private final ExecutionContextUserSupport executionContextUserSupport = new ExecutionContextUserSupport(); |
| 53 | |
| 54 | private ResourceAwareItemReaderItemStream<? extends T> delegate; |
| 55 | |
| 56 | private Resource[] resources; |
| 57 | |
| 58 | private boolean saveState = true; |
| 59 | |
| 60 | private int currentResource = -1; |
| 61 | |
| 62 | // signals there are no resources to read -> just return null on first read |
| 63 | private boolean noInput; |
| 64 | |
| 65 | private boolean strict = false; |
| 66 | |
| 67 | /** |
| 68 | * In strict mode the reader will throw an exception on |
| 69 | * {@link #open(org.springframework.batch.item.ExecutionContext)} if there are no resources to read. |
| 70 | * @param strict false by default |
| 71 | */ |
| 72 | public void setStrict(boolean strict) { |
| 73 | this.strict = strict; |
| 74 | } |
| 75 | |
| 76 | private Comparator<Resource> comparator = new Comparator<Resource>() { |
| 77 | |
| 78 | /** |
| 79 | * Compares resource filenames. |
| 80 | */ |
| 81 | public int compare(Resource r1, Resource r2) { |
| 82 | return r1.getFilename().compareTo(r2.getFilename()); |
| 83 | } |
| 84 | |
| 85 | }; |
| 86 | |
| 87 | public MultiResourceItemReader() { |
| 88 | executionContextUserSupport.setName(ClassUtils.getShortName(MultiResourceItemReader.class)); |
| 89 | } |
| 90 | |
| 91 | /** |
| 92 | * Reads the next item, jumping to next resource if necessary. |
| 93 | */ |
| 94 | public T read() throws Exception, UnexpectedInputException, ParseException { |
| 95 | |
| 96 | if (noInput) { |
| 97 | return null; |
| 98 | } |
| 99 | |
| 100 | // If there is no resource, then this is the first item, set the current |
| 101 | // resource to 0 and open the first delegate. |
| 102 | if (currentResource == -1) { |
| 103 | currentResource = 0; |
| 104 | delegate.setResource(resources[currentResource]); |
| 105 | delegate.open(new ExecutionContext()); |
| 106 | } |
| 107 | |
| 108 | return readNextItem(); |
| 109 | } |
| 110 | |
| 111 | /** |
| 112 | * Use the delegate to read the next item, jump to next resource if current one is exhausted. Items are appended to |
| 113 | * the buffer. |
| 114 | * |
| 115 | * @return next item from input |
| 116 | */ |
| 117 | private T readNextItem() throws Exception { |
| 118 | |
| 119 | T item = delegate.read(); |
| 120 | |
| 121 | while (item == null) { |
| 122 | |
| 123 | currentResource++; |
| 124 | |
| 125 | if (currentResource >= resources.length) { |
| 126 | return null; |
| 127 | } |
| 128 | |
| 129 | delegate.close(); |
| 130 | delegate.setResource(resources[currentResource]); |
| 131 | delegate.open(new ExecutionContext()); |
| 132 | |
| 133 | item = delegate.read(); |
| 134 | } |
| 135 | |
| 136 | return item; |
| 137 | } |
| 138 | |
| 139 | /** |
| 140 | * Close the {@link #setDelegate(ResourceAwareItemReaderItemStream)} reader and reset instance variable values. |
| 141 | */ |
| 142 | public void close() throws ItemStreamException { |
| 143 | delegate.close(); |
| 144 | noInput = false; |
| 145 | } |
| 146 | |
| 147 | /** |
| 148 | * Figure out which resource to start with in case of restart, open the delegate and restore delegate's position in |
| 149 | * the resource. |
| 150 | */ |
| 151 | public void open(ExecutionContext executionContext) throws ItemStreamException { |
| 152 | |
| 153 | Assert.notNull(resources, "Resources must be set"); |
| 154 | |
| 155 | noInput = false; |
| 156 | if (resources.length == 0) { |
| 157 | if (strict) { |
| 158 | throw new IllegalStateException( |
| 159 | "No resources to read. Set strict=false if this is not an error condition."); |
| 160 | } |
| 161 | else { |
| 162 | logger.warn("No resources to read. Set strict=true if this should be an error condition."); |
| 163 | noInput = true; |
| 164 | return; |
| 165 | } |
| 166 | } |
| 167 | |
| 168 | Arrays.sort(resources, comparator); |
| 169 | |
| 170 | if (executionContext.containsKey(executionContextUserSupport.getKey(RESOURCE_KEY))) { |
| 171 | currentResource = executionContext.getInt(executionContextUserSupport.getKey(RESOURCE_KEY)); |
| 172 | |
| 173 | // context could have been saved before reading anything |
| 174 | if (currentResource == -1) { |
| 175 | currentResource = 0; |
| 176 | } |
| 177 | |
| 178 | delegate.setResource(resources[currentResource]); |
| 179 | delegate.open(executionContext); |
| 180 | } |
| 181 | else { |
| 182 | currentResource = -1; |
| 183 | } |
| 184 | } |
| 185 | |
| 186 | /** |
| 187 | * Store the current resource index and position in the resource. |
| 188 | */ |
| 189 | public void update(ExecutionContext executionContext) throws ItemStreamException { |
| 190 | if (saveState) { |
| 191 | executionContext.putInt(executionContextUserSupport.getKey(RESOURCE_KEY), currentResource); |
| 192 | delegate.update(executionContext); |
| 193 | } |
| 194 | } |
| 195 | |
| 196 | /** |
| 197 | * @param delegate reads items from single {@link Resource}. |
| 198 | */ |
| 199 | public void setDelegate(ResourceAwareItemReaderItemStream<? extends T> delegate) { |
| 200 | this.delegate = delegate; |
| 201 | } |
| 202 | |
| 203 | /** |
| 204 | * Set the boolean indicating whether or not state should be saved in the provided {@link ExecutionContext} during |
| 205 | * the {@link ItemStream} call to update. |
| 206 | * |
| 207 | * @param saveState |
| 208 | */ |
| 209 | public void setSaveState(boolean saveState) { |
| 210 | this.saveState = saveState; |
| 211 | } |
| 212 | |
| 213 | /** |
| 214 | * @param comparator used to order the injected resources, by default compares {@link Resource#getFilename()} |
| 215 | * values. |
| 216 | */ |
| 217 | public void setComparator(Comparator<Resource> comparator) { |
| 218 | this.comparator = comparator; |
| 219 | } |
| 220 | |
| 221 | /** |
| 222 | * @param resources input resources |
| 223 | */ |
| 224 | public void setResources(Resource[] resources) { |
| 225 | Assert.notNull(resources, "The resources must not be null"); |
| 226 | this.resources = Arrays.asList(resources).toArray(new Resource[resources.length]); |
| 227 | } |
| 228 | |
| 229 | public Resource getCurrentResource() { |
| 230 | if (currentResource >= resources.length || currentResource < 0) { |
| 231 | return null; |
| 232 | } |
| 233 | return resources[currentResource]; |
| 234 | } |
| 235 | |
| 236 | } |