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Java > Open Source Codes > org > objectstyle > cayenne > access > jdbc > ChunkDirective


1 /* ====================================================================
2  *
3  * The ObjectStyle Group Software License, version 1.1
4  * ObjectStyle Group - http://objectstyle.org/
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6  * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
7  * of the software. All rights reserved.
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24  * and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
25  * Alternately, this acknowlegement may appear in the software itself,
26  * if and wherever such third-party acknowlegements normally appear.
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56 package org.objectstyle.cayenne.access.jdbc;
57
58 import java.io.IOException JavaDoc;
59 import java.io.Writer JavaDoc;
60
61 import org.apache.velocity.context.InternalContextAdapter;
62 import org.apache.velocity.exception.MethodInvocationException;
63 import org.apache.velocity.exception.ParseErrorException;
64 import org.apache.velocity.exception.ResourceNotFoundException;
65 import org.apache.velocity.runtime.directive.Directive;
66 import org.apache.velocity.runtime.parser.node.Node;
67
68 /**
69  * A custom Velocity directive to describe a conditional chunk of a {@link ChainDirective chain}.
70  * Usage of chunk is the following:
71  *
72  * <pre>
73  * #chunk()...#end - e.g. #chunk()A = 5#end
74  * #chunk(condition)...#end - e.g. #chunk($a)A = $a#end</pre>
75  *
76  * <p>If condition is evaluated to false, chunk is not included in the chain,
77  * if it is true, chunk is included, and if it is not the first chunk, it is
78  * prefixed with chain join.
79  *
80  * @since 1.1
81  * @author Andrei Adamchik
82  */
83 public class ChunkDirective extends Directive {
84
85     public String JavaDoc getName() {
86         return "chunk";
87     }
88
89     public int getType() {
90         return BLOCK;
91     }
92
93     public boolean render(InternalContextAdapter context, Writer JavaDoc writer, Node node)
94         throws
95             IOException JavaDoc,
96             ResourceNotFoundException,
97             ParseErrorException,
98             MethodInvocationException {
99
100         // first child is an expression, second is BLOCK
101 if (node.jjtGetNumChildren() > 1 && !node.jjtGetChild(0).evaluate(context)) {
102             // return value is really meaningless in Velocity...whatever
103 return false;
104         }
105
106         // BLOCK is the last child
107 Node block = node.jjtGetChild(node.jjtGetNumChildren() - 1);
108         block.render(context, writer);
109         return true;
110     }
111
112 }
113
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