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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.repeat.policy;
18  
19  import org.springframework.batch.repeat.RepeatContext;
20  import org.springframework.batch.repeat.context.RepeatContextCounter;
21  import org.springframework.batch.repeat.context.RepeatContextSupport;
22  
23  /**
24   * Abstract base class for policies that need to count the number of occurrences
25   * of some event (e.g. an exception type in the context), and terminate based on
26   * a limit for the counter. The value of the counter can be stored between
27   * batches in a nested context, so that the termination decision is based on the
28   * aggregate of a number of sibling batches.
29   * 
30   * @author Dave Syer
31   * 
32   */
33  public abstract class CountingCompletionPolicy extends DefaultResultCompletionPolicy {
34  
35  	/**
36  	 * Session key for global counter.
37  	 */
38  	public static final String COUNT = CountingCompletionPolicy.class.getName() + ".COUNT";
39  
40  	private boolean useParent = false;
41  
42  	private int maxCount = 0;
43  
44  	/**
45  	 * Flag to indicate whether the count is at the level of the parent context,
46  	 * or just local to the context. If true then the count is aggregated among
47  	 * siblings in a nested batch.
48  	 * 
49  	 * @param useParent whether to use the parent context to cache the total
50  	 * count. Default value is false.
51  	 */
52  	public void setUseParent(boolean useParent) {
53  		this.useParent = useParent;
54  	}
55  
56  	/**
57  	 * Setter for maximum value of count before termination.
58  	 * 
59  	 * @param maxCount the maximum number of counts before termination. Default
60  	 * 0 so termination is immediate.
61  	 */
62  	public void setMaxCount(int maxCount) {
63  		this.maxCount = maxCount;
64  	}
65  
66  	/**
67  	 * Extension point for subclasses. Obtain the value of the count in the
68  	 * current context. Subclasses can count the number of attempts or
69  	 * violations and store the result in their context. This policy base class
70  	 * will take care of the termination contract and aggregating at the level
71  	 * of the session if required.
72  	 * 
73  	 * @param context the current context, specific to the subclass.
74  	 * @return the value of the counter in the context.
75  	 */
76  	protected abstract int getCount(RepeatContext context);
77  
78  	/**
79  	 * Extension point for subclasses. Inspect the context and update the state
80  	 * of a counter in whatever way is appropriate. This will be added to the
81  	 * session-level counter if {@link #setUseParent(boolean)} is true.
82  	 * 
83  	 * @param context the current context.
84  	 * 
85  	 * @return the change in the value of the counter (default 0).
86  	 */
87  	protected int doUpdate(RepeatContext context) {
88  		return 0;
89  	}
90  
91  	/*
92  	 * (non-Javadoc)
93  	 * @see org.springframework.batch.repeat.policy.CompletionPolicySupport#isComplete(org.springframework.batch.repeat.BatchContext)
94  	 */
95      @Override
96  	final public boolean isComplete(RepeatContext context) {
97  		int count = ((CountingBatchContext) context).getCounter().getCount();
98  		return count >= maxCount;
99  	}
100 
101 	/*
102 	 * (non-Javadoc)
103 	 * @see org.springframework.batch.repeat.policy.CompletionPolicySupport#start(org.springframework.batch.repeat.BatchContext)
104 	 */
105     @Override
106 	public RepeatContext start(RepeatContext parent) {
107 		return new CountingBatchContext(parent);
108 	}
109 
110 	/*
111 	 * (non-Javadoc)
112 	 * @see org.springframework.batch.repeat.policy.CompletionPolicySupport#update(org.springframework.batch.repeat.BatchContext)
113 	 */
114     @Override
115 	final public void update(RepeatContext context) {
116 		super.update(context);
117 		int delta = doUpdate(context);
118 		((CountingBatchContext) context).getCounter().increment(delta);
119 	}
120 
121 	protected class CountingBatchContext extends RepeatContextSupport {
122 
123 		RepeatContextCounter counter;
124 
125 		public CountingBatchContext(RepeatContext parent) {
126 			super(parent);
127 			counter = new RepeatContextCounter(this, COUNT, useParent);
128 		}
129 
130 		public RepeatContextCounter getCounter() {
131 			return counter;
132 		}
133 
134 	}
135 }