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Java > Open Source Codes > oracle > toplink > essentials > internal > parsing > NullComparisonNode


1 /*
2  * The contents of this file are subject to the terms
3  * of the Common Development and Distribution License
4  * (the "License"). You may not use this file except
5  * in compliance with the License.
6  *
7  * You can obtain a copy of the license at
8  * glassfish/bootstrap/legal/CDDLv1.0.txt or
9  * https://glassfish.dev.java.net/public/CDDLv1.0.html.
10  * See the License for the specific language governing
11  * permissions and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL
14  * HEADER in each file and include the License file at
15  * glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable,
16  * add the following below this CDDL HEADER, with the
17  * fields enclosed by brackets "[]" replaced with your
18  * own identifying information: Portions Copyright [yyyy]
19  * [name of copyright owner]
20  */
21 // Copyright (c) 1998, 2005, Oracle. All rights reserved.
22 package oracle.toplink.essentials.internal.parsing;
23
24 import oracle.toplink.essentials.expressions.*;
25
26 /**
27  * INTERNAL
28  * <p><b>Purpose</b>: This node represents the IS NULL comparisons
29  * <p><b>Responsibilities</b>:<ul>
30  * <li> Generate the correct expression for IS NULL
31  * </ul>
32  * @author Jon Driscoll and Joel Lucuik
33  * @since TopLink 4.0
34  */
35 public class NullComparisonNode extends SimpleConditionalExpressionNode {
36
37     /**
38      * Return a new NullComparisonNode.
39      */
40     public NullComparisonNode() {
41         super();
42     }
43
44     /**
45      * INTERNAL
46      * Validate node and calculate its type.
47      */
48     public void validate(ParseTreeContext context) {
49         TypeHelper typeHelper = context.getTypeHelper();
50         if (left != null) {
51             left.validate(context);
52             left.validateParameter(context, typeHelper.getObjectType());
53         }
54         setType(typeHelper.getBooleanType());
55     }
56
57     /**
58      * INTERNAL
59      * Return a TopLink expression for this node.
60      */
61     public Expression generateExpression(GenerationContext context) {
62         Expression whereClause = getLeft().generateExpression(context);
63         whereClause = whereClause.isNull();
64         return whereClause;
65     }
66
67 }
68
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