ELPageTag


1   /*
2    * $Id: ELPageTag.java 54933 2004-10-16 17:04:52Z germuska $ 
3    *
4    * Copyright 1999-2004 The Apache Software Foundation.
5    * 
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    * 
10   *      http://www.apache.org/licenses/LICENSE-2.0
11   * 
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.strutsel.taglib.bean;
20  
21  import org.apache.struts.taglib.bean.PageTag;
22  import javax.servlet.jsp.JspException  ;
23  import org.apache.strutsel.taglib.utils.EvalHelper;
24  
25  /**
26   * Define a scripting variable that exposes the requested page context
27   * item as a scripting variable and a page scope bean.
28   *<p>
29   * This class is a subclass of the class
30   * <code>org.apache.struts.taglib.bean.PageTag</code> which provides most of
31   * the described functionality.  This subclass allows all attribute values to
32   * be specified as expressions utilizing the JavaServer Pages Standard Library
33   * expression language.
34   *
35   * @version $Rev: 54933 $
36   */
37  public class ELPageTag extends PageTag {
38  
39      /**
40       * Instance variable mapped to "id" tag attribute.
41       * (Mapping set in associated BeanInfo class.)
42       */
43      private String   idExpr;
44      /**
45       * Instance variable mapped to "property" tag attribute.
46       * (Mapping set in associated BeanInfo class.)
47       */
48      private String   propertyExpr;
49  
50      /**
51       * Getter method for "id" tag attribute.
52       * (Mapping set in associated BeanInfo class.)
53       */
54      public String   getIdExpr() { return (idExpr); }
55      /**
56       * Getter method for "property" tag attribute.
57       * (Mapping set in associated BeanInfo class.)
58       */
59      public String   getPropertyExpr() { return (propertyExpr); }
60  
61      /**
62       * Setter method for "id" tag attribute.
63       * (Mapping set in associated BeanInfo class.)
64       */
65      public void setIdExpr(String   idExpr) { this.idExpr = idExpr; }
66      /**
67       * Setter method for "property" tag attribute.
68       * (Mapping set in associated BeanInfo class.)
69       */
70      public void setPropertyExpr(String   propertyExpr) { this.propertyExpr = propertyExpr; }
71  
72      /**
73       * Resets attribute values for tag reuse.
74       */
75      public void release()
76      {
77          super.release();
78          setIdExpr(null);
79          setPropertyExpr(null);
80      }
81      
82      /**
83       * Process the start tag.
84       *
85       * @exception JspException if a JSP exception has occurred
86       */
87      public int doStartTag() throws JspException   {
88          evaluateExpressions();
89          return (super.doStartTag());
90      }
91  
92      /**
93       * Processes all attribute values which use the JSTL expression evaluation
94       * engine to determine their values.
95       *
96       * @exception JspException if a JSP exception has occurred
97       */
98      private void evaluateExpressions() throws JspException   {
99          String    string  = null;
100 
101 
102         if ((string = EvalHelper.evalString("id", getIdExpr(),
103                                             this, pageContext)) != null)
104             setId(string);
105 
106         if ((string = EvalHelper.evalString("property", getPropertyExpr(),
107                                             this, pageContext)) != null)
108             setProperty(string);
109     }
110 }
111
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