TagLibraryValidator


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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  package javax.servlet.jsp.tagext;
19  
20  import java.util.Map  ;
21  
22  /**
23   * Translation-time validator class for a JSP page. 
24   * A validator operates on the XML view associated with the JSP page.
25   *
26   * <p>
27   * The TLD file associates a TagLibraryValidator class and some init
28   * arguments with a tag library.
29   *
30   * <p>
31   * The JSP container is reponsible for locating an appropriate
32   * instance of the appropriate subclass by
33   *
34   * <ul>
35   * <li> new a fresh instance, or reuse an available one
36   * <li> invoke the setInitParams(Map) method on the instance
37   * </ul>
38   *
39   * once initialized, the validate(String, String, PageData) method will
40   * be invoked, where the first two arguments are the prefix
41   * and uri for this tag library in the XML View.  The prefix is intended
42   * to make it easier to produce an error message.  However, it is not
43   * always accurate.  In the case where a single URI is mapped to more 
44   * than one prefix in the XML view, the prefix of the first URI is provided.
45   * Therefore, to provide high quality error messages in cases where the 
46   * tag elements themselves are checked, the prefix parameter should be 
47   * ignored and the actual prefix of the element should be used instead.  
48   * TagLibraryValidators should always use the uri to identify elements 
49   * as beloning to the tag library, not the prefix.
50   *
51   * <p>
52   * A TagLibraryValidator instance
53   * may create auxiliary objects internally to perform
54   * the validation (e.g. an XSchema validator) and may reuse it for all
55   * the pages in a given translation run.
56   *
57   * <p>
58   * The JSP container is not guaranteed to serialize invocations of
59   * validate() method, and TagLibraryValidators should perform any
60   * synchronization they may require.
61   *
62   * <p>
63   * As of JSP 2.0, a JSP container must provide a jsp:id attribute to
64   * provide higher quality validation errors.
65   * The container will track the JSP pages
66   * as passed to the container, and will assign to each element
67   * a unique "id", which is passed as the value of the jsp:id
68   * attribute.  Each XML element in the XML view available will
69   * be extended with this attribute.  The TagLibraryValidator
70   * can then use the attribute in one or more ValidationMessage
71   * objects.  The container then, in turn, can use these
72   * values to provide more precise information on the location
73   * of an error.
74   *
75   * <p>
76   * The actual prefix of the <code>id</code> attribute may or may not be 
77   * <code>jsp</code> but it will always map to the namespace
78   * <code>http://java.sun.com/JSP/Page</code>.  A TagLibraryValidator
79   * implementation must rely on the uri, not the prefix, of the <code>id</code>
80   * attribute.
81   */
82  
83  abstract public class TagLibraryValidator {
84  
85      /**
86       * Sole constructor. (For invocation by subclass constructors, 
87       * typically implicit.)
88       */
89      public TagLibraryValidator() {
90      }
91      
92      /**
93       * Set the init data in the TLD for this validator.
94       * Parameter names are keys, and parameter values are the values.
95       *
96       * @param map A Map describing the init parameters
97       */
98      public void setInitParameters(Map  <String  , Object  > map) {
99      initParameters = map;
100     }
101 
102 
103     /**
104      * Get the init parameters data as an immutable Map.
105      * Parameter names are keys, and parameter values are the values.
106      *
107      * @return The init parameters as an immutable map.
108      */
109     public Map  <String  , Object  > getInitParameters() {
110     return initParameters;
111     }
112 
113     /**
114      * Validate a JSP page.
115      * This will get invoked once per unique tag library URI in the
116      * XML view.  This method will return null if the page is valid; otherwise
117      * the method should return an array of ValidationMessage objects.
118      * An array of length zero is also interpreted as no errors.
119      *
120      * @param prefix the first prefix with which the tag library is 
121      *     associated, in the XML view.  Note that some tags may use 
122      *     a different prefix if the namespace is redefined.
123      * @param uri the tag library's unique identifier
124      * @param page the JspData page object
125      * @return A null object, or zero length array if no errors, an array
126      * of ValidationMessages otherwise.
127      */
128     public ValidationMessage  [] validate(String   prefix, String   uri, 
129         PageData   page) 
130     {
131     return null;
132     }
133 
134     /**
135      * Release any data kept by this instance for validation purposes.
136      */
137     public void release() {
138     initParameters = null;
139     }
140 
141     // Private data
142     private Map  <String  , Object  > initParameters;
143 
144 }
145
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