org.springframework.batch.item.file.MultiResourceItemReader Maven / Gradle / Ivy
/*
* Copyright 2006-2018 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.batch.item.file;
import java.util.Arrays;
import java.util.Comparator;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.batch.item.ExecutionContext;
import org.springframework.batch.item.ItemStream;
import org.springframework.batch.item.ItemStreamException;
import org.springframework.batch.item.ParseException;
import org.springframework.batch.item.ResourceAware;
import org.springframework.batch.item.UnexpectedInputException;
import org.springframework.batch.item.support.AbstractItemStreamItemReader;
import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
/**
* Reads items from multiple resources sequentially - resource list is given by {@link #setResources(Resource[])}, the
* actual reading is delegated to {@link #setDelegate(ResourceAwareItemReaderItemStream)}.
*
* Input resources are ordered using {@link #setComparator(Comparator)} to make sure resource ordering is preserved
* between job runs in restart scenario.
*
*
* @author Robert Kasanicky
* @author Lucas Ward
* @author Mahmoud Ben Hassine
*/
public class MultiResourceItemReader extends AbstractItemStreamItemReader {
private static final Log logger = LogFactory.getLog(MultiResourceItemReader.class);
private static final String RESOURCE_KEY = "resourceIndex";
private ResourceAwareItemReaderItemStream delegate;
private Resource[] resources;
private boolean saveState = true;
private int currentResource = -1;
// signals there are no resources to read -> just return null on first read
private boolean noInput;
private boolean strict = false;
/**
* In strict mode the reader will throw an exception on
* {@link #open(org.springframework.batch.item.ExecutionContext)} if there are no resources to read.
* @param strict false by default
*/
public void setStrict(boolean strict) {
this.strict = strict;
}
private Comparator comparator = new Comparator() {
/**
* Compares resource filenames.
*/
@Override
public int compare(Resource r1, Resource r2) {
return r1.getFilename().compareTo(r2.getFilename());
}
};
public MultiResourceItemReader() {
this.setExecutionContextName(ClassUtils.getShortName(MultiResourceItemReader.class));
}
/**
* Reads the next item, jumping to next resource if necessary.
*/
@Override
public T read() throws Exception, UnexpectedInputException, ParseException {
if (noInput) {
return null;
}
// If there is no resource, then this is the first item, set the current
// resource to 0 and open the first delegate.
if (currentResource == -1) {
currentResource = 0;
delegate.setResource(resources[currentResource]);
delegate.open(new ExecutionContext());
}
return readNextItem();
}
/**
* Use the delegate to read the next item, jump to next resource if current one is exhausted. Items are appended to
* the buffer.
*
* @return next item from input
*/
private T readNextItem() throws Exception {
T item = readFromDelegate();
while (item == null) {
currentResource++;
if (currentResource >= resources.length) {
return null;
}
delegate.close();
delegate.setResource(resources[currentResource]);
delegate.open(new ExecutionContext());
item = readFromDelegate();
}
return item;
}
private T readFromDelegate() throws Exception {
T item = delegate.read();
if(item instanceof ResourceAware){
((ResourceAware) item).setResource(getCurrentResource());
}
return item;
}
/**
* Close the {@link #setDelegate(ResourceAwareItemReaderItemStream)} reader and reset instance variable values.
*/
@Override
public void close() throws ItemStreamException {
super.close();
if(!this.noInput) {
delegate.close();
}
noInput = false;
}
/**
* Figure out which resource to start with in case of restart, open the delegate and restore delegate's position in
* the resource.
*/
@Override
public void open(ExecutionContext executionContext) throws ItemStreamException {
super.open(executionContext);
Assert.notNull(resources, "Resources must be set");
noInput = false;
if (resources.length == 0) {
if (strict) {
throw new IllegalStateException(
"No resources to read. Set strict=false if this is not an error condition.");
}
else {
logger.warn("No resources to read. Set strict=true if this should be an error condition.");
noInput = true;
return;
}
}
Arrays.sort(resources, comparator);
if (executionContext.containsKey(getExecutionContextKey(RESOURCE_KEY))) {
currentResource = executionContext.getInt(getExecutionContextKey(RESOURCE_KEY));
// context could have been saved before reading anything
if (currentResource == -1) {
currentResource = 0;
}
delegate.setResource(resources[currentResource]);
delegate.open(executionContext);
}
else {
currentResource = -1;
}
}
/**
* Store the current resource index and position in the resource.
*/
@Override
public void update(ExecutionContext executionContext) throws ItemStreamException {
super.update(executionContext);
if (saveState) {
executionContext.putInt(getExecutionContextKey(RESOURCE_KEY), currentResource);
delegate.update(executionContext);
}
}
/**
* @param delegate reads items from single {@link Resource}.
*/
public void setDelegate(ResourceAwareItemReaderItemStream delegate) {
this.delegate = delegate;
}
/**
* Set the boolean indicating whether or not state should be saved in the provided {@link ExecutionContext} during
* the {@link ItemStream} call to update.
*
* @param saveState true to update ExecutionContext. False do not update
* ExecutionContext.
*/
public void setSaveState(boolean saveState) {
this.saveState = saveState;
}
/**
* @param comparator used to order the injected resources, by default compares {@link Resource#getFilename()}
* values.
*/
public void setComparator(Comparator comparator) {
this.comparator = comparator;
}
/**
* @param resources input resources
*/
public void setResources(Resource[] resources) {
Assert.notNull(resources, "The resources must not be null");
this.resources = Arrays.asList(resources).toArray(new Resource[resources.length]);
}
/**
* Getter for the current resource.
* @return the current resource or {@code null} if all resources have been
* processed or the first resource has not been assigned yet.
*/
@Nullable
public Resource getCurrentResource() {
if (currentResource >= resources.length || currentResource < 0) {
return null;
}
return resources[currentResource];
}
}