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1   /*
2    * Copyright 2006-2013 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.partition.support;
17  
18  import java.util.Collection;
19  import java.util.Set;
20  
21  import org.springframework.batch.core.StepExecution;
22  import org.springframework.batch.core.partition.PartitionHandler;
23  import org.springframework.batch.core.partition.StepExecutionSplitter;
24  
25  /**
26   * Base {@link PartitionHandler} implementation providing common base
27   * features. Subclasses are expected to implement only the
28   * {@link #doHandle(org.springframework.batch.core.StepExecution, java.util.Set)}
29   * method which returns with the result of the execution(s) or an exception if
30   * the step failed to process.
31   *
32   * @author Sebastien Gerard
33   * @author Dave Syer
34   */
35  public abstract class AbstractPartitionHandler implements PartitionHandler {
36  
37  	private int gridSize = 1;
38  
39  	/**
40  	 * Executes the specified {@link StepExecution} instances and returns an updated
41  	 * view of them. Throws an {@link Exception} if anything goes wrong.
42  	 *
43  	 * @param masterStepExecution the whole partition execution
44  	 * @param partitionStepExecutions the {@link StepExecution} instances to execute
45  	 * @return an updated view of these completed {@link StepExecution} instances
46  	 * @throws Exception if anything goes wrong. This allows implementations to
47  	 * be liberal and rely on the caller to translate an exception into a step
48  	 * failure as necessary.
49  	 */
50  	protected abstract Set<StepExecution> doHandle(StepExecution masterStepExecution,
51  			Set<StepExecution> partitionStepExecutions) throws Exception;
52  
53  	/**
54  	 * @see PartitionHandler#handle(StepExecutionSplitter, StepExecution)
55  	 */
56  	@Override
57  	public Collection<StepExecution> handle(final StepExecutionSplitter stepSplitter,
58  			final StepExecution masterStepExecution) throws Exception {
59  		final Set<StepExecution> stepExecutions = stepSplitter.split(masterStepExecution, gridSize);
60  
61  		return doHandle(masterStepExecution, stepExecutions);
62  	}
63  
64  	/**
65  	 * Returns the number of step executions.
66  	 *
67  	 * @return the number of step executions
68  	 */
69  	public int getGridSize() {
70  		return gridSize;
71  	}
72  
73  	/**
74  	 * Passed to the {@link StepExecutionSplitter} in the
75  	 * {@link #handle(StepExecutionSplitter, StepExecution)} method, instructing
76  	 * it how many {@link StepExecution} instances are required, ideally. The
77  	 * {@link StepExecutionSplitter} is allowed to ignore the grid size in the
78  	 * case of a restart, since the input data partitions must be preserved.
79  	 *
80  	 * @param gridSize the number of step executions that will be created
81  	 */
82  	public void setGridSize(int gridSize) {
83  		this.gridSize = gridSize;
84  	}
85  
86  }
87