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1   /*
2    * $Id: Bean.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.commons.logging.Log;
26  import org.apache.commons.logging.LogFactory;
27  import org.apache.struts2.views.annotations.StrutsTag;
28  import org.apache.struts2.views.annotations.StrutsTagAttribute;
29  
30  import com.opensymphony.xwork2.inject.Inject;
31  import com.opensymphony.xwork2.util.ClassLoaderUtil;
32  import com.opensymphony.xwork2.ObjectFactory;
33  import com.opensymphony.xwork2.util.OgnlUtil;
34  import com.opensymphony.xwork2.util.ValueStack;
35  
36  /***
37   * <!-- START SNIPPET: javadoc -->
38   * <p>Instantiates a class that conforms to the JavaBeans specification. This tag has a body which can contain
39   * a number of {@link Param} elements to set any mutator methods on that class.</p>
40   * <p/>
41   * <p>If the id attribute is set on the BeanTag, it will place the instantiated bean into the
42   * stack's Context.</p>
43   * <p/>
44   * <!-- END SNIPPET: javadoc -->
45   *
46   *
47   * <!-- START SNIPPET: params -->
48   * <ul>
49   *      <li>id - the stack's context id (if supplied) that the created bean will be store under</li>
50   *      <li>name* - the class name of the bean to be instantiated (must respect JavaBean specification)</li>
51   * </ul>
52   * <!-- END SNIPPET: params -->
53   *
54   *
55   * <p>Examples:</p>
56   * <p/>
57   * <pre>
58   * <!-- START SNIPPET: examples -->
59   * &lt;-- in freemarker form --&gt;
60   * [@s.bean name="org.apache.struts2.example.counter.SimpleCounter" id="counter"]
61   *   [s:param name="foo" value="BAR"/]
62   *   The value of foo is : [s:property value="foo"/], when inside the bean tag.<br />
63   * [/s:bean]
64   *
65   * &lt;-- in jsp form --&gt;
66   * &lt;s:bean name="org.apache.struts2.example.counter.SimpleCounter" id="counter"&gt;
67   *   &lt;s:param name="foo" value="BAR" /&gt;
68   *   The value of foot is : &lt;s:property value="foo"/&gt;, when inside the bean tag &lt;br /&gt;
69   * &lt;/s:bean&gt;
70   * <!-- END SNIPPET: examples -->
71   * </pre>
72   * <p/>
73   *
74   * <!-- START SNIPPET: examplesdescription -->
75   * <p>This example instantiates a bean called SimpleCounter and sets the foo property (setFoo('BAR')). The
76   * SimpleCounter object is then pushed onto the Valuestack, which means that we can call its accessor methods (getFoo())
77   * with the Property tag and get their values.</p>
78   * <p/>
79   * <p>In the above example, the id has been set to a value of <i>counter</i>. This means that the SimpleCounter class
80   * will be placed into the stack's context. You can access the SimpleCounter class using a Struts tag:</p>
81   * <p/>
82   * <pre>
83   * &lt;-- jsp form --&gt;
84   * &lt;s:property value="#counter" /&gt;
85   *
86   * &lt;-- freemarker form --&gt;
87   * [s:property value="#counter.foo"/]
88   * </pre>
89   * <p/>
90   * <p>In the property tag example, the <i>#</i> tells Ognl to search the context for the SimpleCounter class which has
91   * an id(key) of <i>counter</i></p>
92   * <!-- END SNIPPET: examplesdescription -->
93   *
94   * @see Param
95   */
96  @StrutsTag(name="bean", tldTagClass="org.apache.struts2.views.jsp.BeanTag",
97          description="Instantiate a JavaBean and place it in the context")
98  public class Bean extends Component {
99      protected static Log log = LogFactory.getLog(Bean.class);
100 
101     protected Object bean;
102     protected String name;
103     protected ObjectFactory objectFactory;
104 
105     public Bean(ValueStack stack) {
106         super(stack);
107     }
108     
109     @Inject
110     public void setObjectFactory(ObjectFactory objectFactory) {
111         this.objectFactory = objectFactory;
112     }
113 
114     public boolean start(Writer writer) {
115         boolean result = super.start(writer);
116 
117         ValueStack stack = getStack();
118 
119         try {
120             String beanName = findString(name, "name", "Bean name is required. Example: com.acme.FooBean");
121             bean = objectFactory.buildBean(ClassLoaderUtil.loadClass(beanName, getClass()), stack.getContext());
122         } catch (Exception e) {
123             log.error("Could not instantiate bean", e);
124 
125             return false;
126         }
127 
128         // push bean on stack
129         stack.push(bean);
130 
131         // store for reference later
132         if (getId() != null) {
133             getStack().getContext().put(getId(), bean);
134         }
135 
136         return result;
137     }
138 
139     public boolean end(Writer writer, String body) {
140         ValueStack stack = getStack();
141         stack.pop();
142 
143         return super.end(writer, body);
144     }
145 
146     public void addParameter(String key, Object value) {
147         OgnlUtil.setProperty(key, value, bean, getStack().getContext());
148     }
149 
150     @StrutsTagAttribute(description="The class name of the bean to be instantiated (must respect JavaBean specification)",
151                         required=true)
152     public void setName(String name) {
153         this.name = name;
154     }
155 }