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Java > Open Source Codes > org > apache > commons > jelly > impl > DynamicDynaBeanTag


1 /*
2  * Copyright 2002,2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.jelly.impl;
17
18 import java.util.HashSet JavaDoc;
19 import java.util.Iterator JavaDoc;
20 import java.util.Map JavaDoc;
21 import java.util.Set JavaDoc;
22
23 import org.apache.commons.beanutils.DynaClass;
24 import org.apache.commons.jelly.DynaBeanTagSupport;
25 import org.apache.commons.jelly.JellyTagException;
26 import org.apache.commons.jelly.MissingAttributeException;
27 import org.apache.commons.jelly.XMLOutput;
28 import org.apache.commons.jelly.expression.Expression;
29
30 /**
31  * This tag is bound onto a {@link DynaClass} instance.
32  * When the tag is invoked a {@link DynaBean will be created using the tags attributes.
33  * So this class is like a {@link DynaBean} implemenation of {@link DynamicBeanTag}
34  *
35  * @author <a HREF="mailto:jstrachan@apache.org">James Strachan</a>
36  * @version $Revision: 155420 $
37  */
38 public class DynamicDynaBeanTag extends DynaBeanTagSupport implements BeanSource {
39
40     /** the bean class */
41     private DynaClass beanClass;
42
43     /**
44      * the tag attribute name that is used to declare the name
45      * of the variable to export after running this tag
46      */
47     private String JavaDoc variableNameAttribute;
48
49     /** the current variable name that the bean should be exported as */
50     private String JavaDoc var;
51
52     /** the set of attribute names we've already set */
53     private Set JavaDoc setAttributesSet = new HashSet JavaDoc();
54
55     /** the attribute definitions */
56     private Map JavaDoc attributes;
57
58     public DynamicDynaBeanTag(DynaClass beanClass, Map JavaDoc attributes, String JavaDoc variableNameAttribute) {
59         this.beanClass = beanClass;
60         this.attributes = attributes;
61         this.variableNameAttribute = variableNameAttribute;
62     }
63
64     public void beforeSetAttributes() throws JellyTagException {
65         // create a new dynabean before the attributes are set
66 try {
67             setDynaBean( beanClass.newInstance() );
68         } catch (IllegalAccessException JavaDoc e) {
69             throw new JellyTagException("Could not instantiate dynabean",e);
70         } catch (InstantiationException JavaDoc e) {
71             throw new JellyTagException("Could not instantiate dynabean",e);
72         }
73
74         setAttributesSet.clear();
75     }
76
77     public void setAttribute(String JavaDoc name, Object JavaDoc value) throws JellyTagException {
78         boolean isVariableName = false;
79         if (variableNameAttribute != null ) {
80             if ( variableNameAttribute.equals( name ) ) {
81                 if (value == null) {
82                     var = null;
83                 }
84                 else {
85                     var = value.toString();
86                 }
87                 isVariableName = true;
88             }
89         }
90         if (! isVariableName) {
91
92             // #### strictly speaking we could
93 // know what attributes are specified at compile time
94 // so this dynamic set is unnecessary
95 setAttributesSet.add(name);
96
97             // we could maybe implement attribute specific validation here
98
99             super.setAttribute(name, value);
100         }
101     }
102
103     // Tag interface
104 //-------------------------------------------------------------------------
105 public void doTag(XMLOutput output) throws JellyTagException {
106
107         // lets find any attributes that are not set and
108 for ( Iterator JavaDoc iter = attributes.values().iterator(); iter.hasNext(); ) {
109             Attribute attribute = (Attribute) iter.next();
110             String JavaDoc name = attribute.getName();
111             if ( ! setAttributesSet.contains( name ) ) {
112                 if ( attribute.isRequired() ) {
113                     throw new MissingAttributeException(name);
114                 }
115                 // lets get the default value
116 Object JavaDoc value = null;
117                 Expression expression = attribute.getDefaultValue();
118                 if ( expression != null ) {
119                     value = expression.evaluate(context);
120                 }
121
122                 // only set non-null values?
123 if ( value != null ) {
124                     super.setAttribute(name, value);
125                 }
126             }
127         }
128
129         invokeBody(output);
130
131         // export the bean if required
132 if ( var != null ) {
133             context.setVariable(var, getDynaBean());
134         }
135     }
136
137     // Properties
138 //-------------------------------------------------------------------------
139 /**
140      * @return the bean that has just been created
141      */
142     public Object JavaDoc getBean() {
143         return getDynaBean();
144     }
145 }
146
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