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Java > Open Source Codes > org > apache > taglibs > session > ExistsAttributeTag


1 /*
2  * Copyright 1999,2004 The Apache Software Foundation.
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.apache.taglibs.session;
18
19 import java.util.*;
20 import javax.servlet.*;
21 import javax.servlet.http.*;
22 import javax.servlet.jsp.*;
23 import javax.servlet.jsp.tagext.*;
24
25 /**
26  * JSP Tag <b>existsAttribute</b>, used to determine if an HttpSession
27  * attribute exists.
28  * <p>
29  * Includes the body of the tag if the attribute exists.
30  * <p>
31  * You can set the optional tag attribute <b>value</b> to <i>true</i> or
32  * <i>false</i>. The body of the tag is included if existsAttribute matches
33  * the value.
34  * <p>
35  * JSP Tag Lib Descriptor
36  * <p><pre>
37  * &lt;name&gt;existsAttribute&lt;/name&gt;
38  * &lt;tagclass&gt;org.apache.taglibs.session.ExistsAttributeTag&lt;/tagclass&gt;
39  * &lt;bodycontent&gt;JSP&lt;/bodycontent&gt;
40  * &lt;info&gt;Includes the body of the tag if the session attribute exists.&lt;/info&gt;
41  * &lt;attribute&gt;
42  * &lt;name&gt;name&lt;/name&gt;
43  * &lt;required&gt;true&lt;/required&gt;
44  * &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
45  * &lt;/attribute&gt;
46  * &lt;attribute&gt;
47  * &lt;name&gt;value&lt;/name&gt;
48  * &lt;required&gt;false&lt;/required&gt;
49  * &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
50  * &lt;/attribute&gt;
51  * </pre>
52  *
53  * @author Glenn Nielsen
54  */

55
56 public class ExistsAttributeTag extends TagSupport
57 {
58     // Name of session attribute
59
private String JavaDoc name = null;
60     // Value that existsAttribute must match
61
private boolean value = true;
62
63     /**
64      * Includes the body of the tag if the session attribute exists.
65      *
66      * @return SKIP_BODY if existsAttribute doesn't match value, EVAL_BODY_include if existsAttribute matches value
67      */

68     public final int doStartTag() throws JspException
69     {
70     boolean result = false;
71
72     // Try to get the session attribute
73
if( pageContext.getSession().getAttribute(name) != null )
74         result = true;
75
76     if( value == result )
77         return EVAL_BODY_INCLUDE;
78     return SKIP_BODY;
79     }
80
81     /**
82      * Set the required tag attribute <b>name</b>.
83      *
84      * @param String name of session attribute
85      */

86     public final void setName(String JavaDoc str)
87     {
88     name = str;
89     }
90
91     /**
92      * Set the optional tag attribute <b>value</b> to true or false.
93      *
94      * @param boolean true or false
95      */

96     public final void setValue(boolean value)
97     {
98     this.value = value;
99     }
100
101 }
102
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