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Java > Open Source Codes > org > apache > taglibs > request > ExistsQueryStringTag


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.request;
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>existsquerystring</b>, used to determine if an HttpServletRequest
27  * querystring parameter exists.
28  * <p>
29  * Includes the body of the tag if the querystring parameter exists.
30  * <p>
31  * You can set the optional tag querystring <b>value</b> to <i>true</i> or
32  * <i>false</i>. The body of the tag is included if existsquerystring matches
33  * the value.
34  * <p>
35  * JSP Tag Lib Descriptor
36  * <p><pre>
37  * &lt;name&gt;existsquerystring&lt;/name&gt;
38  * &lt;tagclass&gt;org.apache.taglibs.request.ExistsQueryStringTag&lt;/tagclass&gt;
39  * &lt;bodycontent&gt;JSP&lt;/bodycontent&gt;
40  * &lt;info&gt;Includes the body of the tag if the request querystring parameter 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 ExistsQueryStringTag extends TagSupport
57 {
58     private String JavaDoc name = null;
59     private boolean value = true;
60
61     /**
62      * Includes the body of the tag if the request querystring parameter exists.
63      *
64      * @return SKIP_BODY if existsquerystring doesn't match value, EVAL_BODY_include if existsquerystring matches value
65      */
66     public final int doStartTag() throws JspException
67     {
68     boolean result = false;
69     String JavaDoc query =
70         ((HttpServletRequest)pageContext.getRequest()).getQueryString();
71
72         if( query != null ) {
73             StringTokenizer st = new StringTokenizer(query,"&");
74             String JavaDoc prefix = name + "=";
75             while( st.hasMoreTokens() ) {
76                 if( st.nextToken().startsWith(prefix) ) {
77                     result = true;
78                     break;
79                 }
80             }
81         }
82
83     if( value == result )
84         return EVAL_BODY_INCLUDE;
85
86     return SKIP_BODY;
87     }
88
89     /**
90      * Set the required tag attribute <b>name</b>.
91      *
92      * @param String name of input parameter in querystring
93      */
94     public final void setName(String JavaDoc str)
95     {
96     name = str;
97     }
98
99     /**
100      * Set the optional tag attribute <b>value</b> to true or false.
101      *
102      * @param boolean true or false
103      */
104     public final void setValue(boolean value)
105     {
106     this.value = value;
107     }
108
109 }
110
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