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Java > Open Source Codes > javax > servlet > jsp > tagext > TagExtraInfo


1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18  
19 package javax.servlet.jsp.tagext;
20
21 /**
22  * Optional class provided by the tag library author to describe additional
23  * translation-time information not described in the TLD.
24  * The TagExtraInfo class is mentioned in the Tag Library Descriptor file (TLD).
25  *
26  * <p>
27  * This class can be used:
28  * <ul>
29  * <li> to indicate that the tag defines scripting variables
30  * <li> to perform translation-time validation of the tag attributes.
31  * </ul>
32  *
33  * <p>
34  * It is the responsibility of the JSP translator that the initial value
35  * to be returned by calls to getTagInfo() corresponds to a TagInfo
36  * object for the tag being translated. If an explicit call to
37  * setTagInfo() is done, then the object passed will be returned in
38  * subsequent calls to getTagInfo().
39  *
40  * <p>
41  * The only way to affect the value returned by getTagInfo()
42  * is through a setTagInfo() call, and thus, TagExtraInfo.setTagInfo() is
43  * to be called by the JSP translator, with a TagInfo object that
44  * corresponds to the tag being translated. The call should happen before
45  * any invocation on validate() and before any invocation on
46  * getVariableInfo().
47  *
48  * <p>
49  * <tt>NOTE:</tt> It is a (translation time) error for a tag definition
50  * in a TLD with one or more variable subelements to have an associated
51  * TagExtraInfo implementation that returns a VariableInfo array with
52  * one or more elements from a call to getVariableInfo().
53  */
54
55 public abstract class TagExtraInfo {
56
57     /**
58      * Sole constructor. (For invocation by subclass constructors,
59      * typically implicit.)
60      */
61     public TagExtraInfo() {
62     }
63     
64     /**
65      * information on scripting variables defined by the tag associated with
66      * this TagExtraInfo instance.
67      * Request-time attributes are indicated as such in the TagData parameter.
68      *
69      * @param data The TagData instance.
70      * @return An array of VariableInfo data, or null or a zero length array
71      * if no scripting variables are to be defined.
72      */
73     public VariableInfo JavaDoc[] getVariableInfo(TagData JavaDoc data) {
74     return ZERO_VARIABLE_INFO;
75     }
76
77     /**
78      * Translation-time validation of the attributes.
79      * Request-time attributes are indicated as such in the TagData parameter.
80      * Note that the preferred way to do validation is with the validate()
81      * method, since it can return more detailed information.
82      *
83      * @param data The TagData instance.
84      * @return Whether this tag instance is valid.
85      * @see TagExtraInfo#validate
86      */
87
88     public boolean isValid(TagData JavaDoc data) {
89     return true;
90     }
91
92     /**
93      * Translation-time validation of the attributes.
94      * Request-time attributes are indicated as such in the TagData parameter.
95      * Because of the higher quality validation messages possible,
96      * this is the preferred way to do validation (although isValid()
97      * still works).
98      *
99      * <p>JSP 2.0 and higher containers call validate() instead of isValid().
100      * The default implementation of this method is to call isValid(). If
101      * isValid() returns false, a generic ValidationMessage[] is returned
102      * indicating isValid() returned false.</p>
103      *
104      * @param data The TagData instance.
105      * @return A null object, or zero length array if no errors, an
106      * array of ValidationMessages otherwise.
107      * @since 2.0
108      */
109     public ValidationMessage JavaDoc[] validate( TagData JavaDoc data ) {
110     ValidationMessage JavaDoc[] result = null;
111
112     if( !isValid( data ) ) {
113         result = new ValidationMessage JavaDoc[] {
114         new ValidationMessage JavaDoc( data.getId(), "isValid() == false" ) };
115     }
116
117     return result;
118     }
119
120     /**
121      * Set the TagInfo for this class.
122      *
123      * @param tagInfo The TagInfo this instance is extending
124      */
125     public final void setTagInfo(TagInfo JavaDoc tagInfo) {
126     this.tagInfo = tagInfo;
127     }
128
129     /**
130      * Get the TagInfo for this class.
131      *
132      * @return the taginfo instance this instance is extending
133      */
134     public final TagInfo JavaDoc getTagInfo() {
135     return tagInfo;
136     }
137     
138     // private data
139 private TagInfo JavaDoc tagInfo;
140
141     // zero length VariableInfo array
142 private static final VariableInfo JavaDoc[] ZERO_VARIABLE_INFO = { };
143 }
144
145
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