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1   /*
2    * $Id: Push.java 497654 2007-01-19 00:21:57Z rgielen $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *  http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  package org.apache.struts2.components;
22  
23  import java.io.Writer;
24  
25  import org.apache.struts2.views.annotations.StrutsTag;
26  import org.apache.struts2.views.annotations.StrutsTagAttribute;
27  
28  import com.opensymphony.xwork2.util.ValueStack;
29  
30  /***
31   * <!-- START SNIPPET: javadoc -->
32   * <p>Push value on stack for simplified usage.</p>
33   * <!-- END SNIPPET: javadoc -->
34   *
35   * <!-- START SNIPPET: params -->
36   * <ul>
37   *      <li>value* (Object) - value to be pushed into the top of the stack</li>
38   * </ul>
39   * <!-- END SNIPPET: params -->
40   *
41   *
42   * <p/> <b>Examples</b>
43   * <pre>
44   * <!-- START SNIPPET: example1 -->
45   * &lt;s:push value="user"&gt;
46   *     &lt;s:propery value="firstName" /&gt;
47   *     &lt;s:propery value="lastName" /&gt;
48   * &lt;/s:push&gt;
49   * <!-- END SNIPPET: example1 -->
50   * </pre>
51   *
52   * <!-- START SNIPPET: example1description -->
53   * Pushed user into the stack, and hence property tag could access user's properties
54   * (firstName, lastName etc) since user is not at the top of the stack
55   * <!-- END SNIPPET: example1description -->
56   *
57   * <pre>
58   * <!-- START SNIPPET: example2 -->
59   *  &lt;s:push value="myObject"&gt;                              ----- (1)
60   *       &lt;s:bean name="jp.SomeBean" id="myBean"/&gt;        ----- (2)
61   *          &lt;s:param name="myParam" value="top"/&gt;        ----- (3)
62   *       &lt;/s:bean&gt;
63   *   &lt;/s:push&gt;
64   * <!-- END SNIPPET: example2 -->
65   * </pre>
66   *
67   * <pre>
68   * <!-- START SNIPPET: example2description -->
69   * when in (1), myObject is at the top of the stack
70   * when in (2), jp.SomeBean is in the top of stack, also in stack's context with key myBean
71   * when in (3), top will get the jp.SomeBean instance
72   * <!-- END SNIPPET: example2description -->
73   * </pre>
74   *
75   * <pre>
76   * <!-- START SNIPPET: example3 -->
77   * &lt;s:push value="myObject"&gt;                                       ---(A)
78   *    &lt;s:bean name="jp.SomeBean" id="myBean"/&gt;                   ---(B)
79   *       &lt;s:param name="myParam" value="top.mySomeOtherValue"/&gt;  ---(C)
80   *    &lt;/s:bean&gt;
81   * &lt;/s:push&gt;
82   * <!-- END SNIPPET: example3 -->
83   * </pre>
84   *
85   * <pre>
86   * <!-- START SNIPPET: example3description -->
87   * when in (A), myObject is at the top of the stack
88   * when in (B), jp.SomeBean is at the top of the stack, also in context with key myBean
89   * when in (C), top refers to jp.SomeBean instance. so top.mySomeOtherValue would invoke SomeBean's mySomeOtherValue() method
90   * <!-- END SNIPPET: example3description -->
91   * </pre>
92   *
93   * <pre>
94   * <!-- START SNIPPET: example4 -->
95   * &lt;s:push value="myObject"&gt;                                 ---- (i)
96   *    &lt;s:bean name="jp.SomeBean" id="myBean"/&gt;             ---- (ii)
97   *       &lt;s:param name="myParam" value="[1].top"/&gt;         -----(iii)
98   *    &lt;/s:bean&gt;
99   * &lt;/s:push&gt;
100  * <!-- END SNIPPET: example4 -->
101  * </pre>
102  *
103  * <pre>
104  * <!-- START SNIPPET: example4description -->
105  * when in (i), myObject is at the top of the stack
106  * when in (ii), jp.SomeBean is at the top of the stack, followed by myObject
107  * when in (iii), [1].top will returned top of the cut of stack starting from myObject, namely myObject itself
108  * <!-- END SNIPPET: example4description -->
109  * </pre>
110  *
111  */
112 @StrutsTag(name="push", tldTagClass="org.apache.struts2.views.jsp.PushTag", description="Push value on stack for simplified usage.")
113 public class Push extends Component {
114     protected String value;
115     protected boolean pushed;
116 
117     public Push(ValueStack stack) {
118         super(stack);
119     }
120 
121     public boolean start(Writer writer) {
122         boolean result = super.start(writer);
123 
124         ValueStack stack = getStack();
125 
126         if (stack != null) {
127             stack.push(findValue(value, "value", "You must specify a value to push on the stack. Example: person"));
128             pushed = true;
129         } else {
130             pushed = false; // need to ensure push is assigned, otherwise we may have a leftover value
131         }
132 
133         return result;
134     }
135 
136     public boolean end(Writer writer, String body) {
137         ValueStack stack = getStack();
138 
139         if (pushed && (stack != null)) {
140             stack.pop();
141         }
142 
143         return super.end(writer, body);
144     }
145 
146     @StrutsTagAttribute(description="Value to push on stack", required=true)
147     public void setValue(String value) {
148         this.value = value;
149     }
150 }