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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;
18  
19  
20  /**
21   * Interface for batch completion policies, to enable batch operations to
22   * strategise normal completion conditions. Stateful implementations of batch
23   * iterators should <em>only</em> update state using the update method. If you
24   * need custom behaviour consider extending an existing implementation or using
25   * the composite provided.
26   * 
27   * @author Dave Syer
28   * 
29   */
30  public interface CompletionPolicy {
31  
32  	/**
33  	 * Determine whether a batch is complete given the latest result from the
34  	 * callback. If this method returns true then
35  	 * {@link #isComplete(RepeatContext)} should also (but not necessarily vice
36  	 * versa, since the answer here depends on the result).
37  	 * 
38  	 * @param context the current batch context.
39  	 * @param result the result of the latest batch item processing.
40  	 * 
41  	 * @return true if the batch should terminate.
42  	 * 
43  	 * @see #isComplete(RepeatContext)
44  	 */
45  	boolean isComplete(RepeatContext context, RepeatStatus result);
46  
47  	/**
48  	 * Allow policy to signal completion according to internal state, without
49  	 * having to wait for the callback to complete.
50  	 * 
51  	 * @param context the current batch context.
52  	 * 
53  	 * @return true if the batch should terminate.
54  	 */
55  	boolean isComplete(RepeatContext context);
56  
57  	/**
58  	 * Create a new context for the execution of a batch. N.B. implementations
59  	 * should <em>not</em> return the parent from this method - they must
60  	 * create a new context to meet the specific needs of the policy. The best
61  	 * way to do this might be to override an existing implementation and use
62  	 * the {@link RepeatContext} to store state in its attributes.
63  	 * 
64  	 * @param parent the current context if one is already in progress.
65  	 * @return a context object that can be used by the implementation to store
66  	 * internal state for a batch.
67  	 */
68  	RepeatContext start(RepeatContext parent);
69  
70  	/**
71  	 * Give implementations the opportunity to update the state of the current
72  	 * batch. Will be called <em>once</em> per callback, after it has been
73  	 * launched, but not necessarily after it completes (if the batch is
74  	 * asynchronous).
75  	 * 
76  	 * @param context the value returned by start.
77  	 */
78  	void update(RepeatContext context);
79  
80  }