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Java > Open Source Codes > org > apache > velocity > runtime > parser > node > ASTAndNode


1 package org.apache.velocity.runtime.parser.node;
2
3 /*
4  * Copyright 2000-2001,2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License");
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 import org.apache.velocity.context.InternalContextAdapter;
20 import org.apache.velocity.runtime.parser.Parser;
21 import org.apache.velocity.exception.MethodInvocationException;
22
23 /**
24  * Please look at the Parser.jjt file which is
25  * what controls the generation of this class.
26  *
27  * @author <a HREF="mailto:jvanzyl@apache.org">Jason van Zyl</a>
28  * @author <a HREF="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
29  * @version $Id: ASTAndNode.java,v 1.8.8.1 2004/03/03 23:22:58 geirm Exp $
30  */
31 public class ASTAndNode extends SimpleNode
32 {
33     public ASTAndNode(int id)
34     {
35         super(id);
36     }
37
38     public ASTAndNode(Parser p, int id)
39     {
40         super(p, id);
41     }
42
43     /** Accept the visitor. **/
44     public Object JavaDoc jjtAccept(ParserVisitor visitor, Object JavaDoc data)
45     {
46         return visitor.visit(this, data);
47     }
48
49     /**
50      * Returns the value of the expression.
51      * Since the value of the expression is simply the boolean
52      * result of evaluate(), lets return that.
53      */
54     public Object JavaDoc value(InternalContextAdapter context )
55         throws MethodInvocationException
56     {
57         return new Boolean JavaDoc( evaluate( context ) );
58     }
59
60     /**
61      * logical and :
62      * null && right = false
63      * left && null = false
64      * null && null = false
65      */
66     public boolean evaluate( InternalContextAdapter context)
67         throws MethodInvocationException
68     {
69         Node left = jjtGetChild(0);
70         Node right = jjtGetChild(1);
71
72         /*
73          * if either is null, lets log and bail
74          */
75
76         if (left == null || right == null)
77         {
78             rsvc.error( ( left == null ? "Left" : "Right" ) + " side of '&&' operation is null."
79                            + " Operation not possible. "
80                            + context.getCurrentTemplateName() + " [line " + getLine()
81                            + ", column " + getColumn() + "]");
82             return false;
83         }
84         
85         /*
86          * short circuit the test. Don't eval the RHS if the LHS is false
87          */
88
89         if( left.evaluate( context ) )
90         {
91             if ( right.evaluate( context ) )
92             {
93                 return true;
94             }
95         }
96            
97         return false;
98     }
99 }
100
101
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