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Java > Open Source Codes > org > apache > taglibs > standard > tag > el > fmt > RequestEncodingTag


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.standard.tag.el.fmt;
18
19 import javax.servlet.jsp.JspException JavaDoc;
20
21 import org.apache.taglibs.standard.lang.support.ExpressionEvaluatorManager;
22 import org.apache.taglibs.standard.tag.common.fmt.RequestEncodingSupport;
23
24 /**
25  * <p>A handler for &lt;requestEncoding&gt; that accepts attributes as Strings
26  * and evaluates them as expressions at runtime.</p>
27  *
28  * @author Jan Luehe
29  */
30
31 public class RequestEncodingTag extends RequestEncodingSupport {
32
33     //*********************************************************************
34 // 'Private' state (implementation details)
35
36     private String JavaDoc value_; // stores EL-based property
37
38
39     //*********************************************************************
40 // Constructor
41
42     /**
43      * Constructs a new RequestEncodingTag. As with TagSupport, subclasses
44      * should not provide other constructors and are expected to call
45      * the superclass constructor
46      */
47     public RequestEncodingTag() {
48         super();
49         init();
50     }
51
52
53     //*********************************************************************
54 // Tag logic
55
56     // evaluates expression and chains to parent
57 public int doStartTag() throws JspException JavaDoc {
58
59         // evaluate any expressions we were passed, once per invocation
60 evaluateExpressions();
61
62     // chain to the parent implementation
63 return super.doStartTag();
64     }
65
66     // Releases any resources we may have (or inherit)
67 public void release() {
68         super.release();
69         init();
70     }
71
72
73     //*********************************************************************
74 // Accessor methods
75
76     // for EL-based attribute
77 public void setValue(String JavaDoc value_) {
78         this.value_ = value_;
79     }
80
81
82     //*********************************************************************
83 // Private (utility) methods
84
85     // (re)initializes state (during release() or construction)
86 private void init() {
87         // null implies "no expression"
88 value_ = null;
89     }
90
91     // Evaluates expressions as necessary
92 private void evaluateExpressions() throws JspException JavaDoc {
93         /*
94          * Note: we don't check for type mismatches here; we assume
95          * the expression evaluator will return the expected type
96          * (by virtue of knowledge we give it about what that type is).
97          * A ClassCastException here is truly unexpected, so we let it
98          * propagate up.
99          */
100
101     if (value_ != null) {
102         value = (String JavaDoc) ExpressionEvaluatorManager.evaluate(
103             "value", value_, String JavaDoc.class, this, pageContext);
104     }
105     }
106 }
107
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