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


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>querystring</b>, used to output the value for a single
27  * HttpServletRequest querystring parameter named with <b>name</b>.
28  * <p>
29  * JSP Tag Lib Descriptor
30  * <p><pre>
31  * &lt;name&gt;querystring&lt;/name&gt;
32  * &lt;tagclass&gt;org.apache.taglibs.request.QueryStringTag&lt;/tagclass&gt;
33  * &lt;bodycontent&gt;empty&lt;/bodycontent&gt;
34  * &lt;info&gt;Used to output the value of a single querystring parameter.&lt;/info&gt;
35  * &lt;attribute&gt;
36  * &lt;name&gt;name&lt;/name&gt;
37  * &lt;required&gt;true&lt;/required&gt;
38  * &lt;rtexprvalue&gt;false&lt;/rtexprvalue&gt;
39  * &lt;/attribute&gt;
40  * </pre>
41  *
42  * @author Glenn Nielsen
43  */
44
45 public class QueryStringTag extends TagSupport
46 {
47     private String JavaDoc name = null;
48
49     /**
50      * Method called at end of Tag to output querystring parameter value
51      *
52      * @return EVAL_PAGE
53      */
54     public final int doEndTag() throws JspException
55     {
56         String JavaDoc query =
57             ((HttpServletRequest)pageContext.getRequest()).getQueryString();
58         String JavaDoc value = null;
59         if( query != null ) {
60             StringTokenizer st = new StringTokenizer(query,"&");
61             String JavaDoc prefix = name + "=";
62             String JavaDoc tmp = null;
63             while( st.hasMoreTokens() ) {
64                 tmp = st.nextToken();
65                 if( tmp.startsWith(prefix) ) {
66                     value = tmp.substring(prefix.length());
67                     break;
68                 }
69             }
70         }
71
72     if( value == null )
73         value = "";
74
75     try {
76         pageContext.getOut().write("" + value);
77     } catch(Exception JavaDoc e) {
78         throw new JspException("IO Error: " + e.getMessage());
79     }
80
81     return EVAL_PAGE;
82     }
83
84     /**
85      * Set the required tag attribute <b>name</b>.
86      *
87      * @param String name of input parameter in querystring
88      */
89     public final void setName(String JavaDoc str)
90     {
91     name = str;
92     }
93
94 }
95
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