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Java > Open Source Codes > org > displaytag > decorator > DefaultDecoratorFactory


1 /**
2  * Licensed under the Artistic License; you may not use this file
3  * except in compliance with the License.
4  * You may obtain a copy of the License at
5  *
6  * http://displaytag.sourceforge.net/license.html
7  *
8  * THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR
9  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
10  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
11  */
12 package org.displaytag.decorator;
13
14 import javax.servlet.jsp.PageContext JavaDoc;
15
16 import org.apache.commons.lang.StringUtils;
17 import org.displaytag.exception.DecoratorException;
18 import org.displaytag.exception.DecoratorInstantiationException;
19 import org.displaytag.properties.MediaTypeEnum;
20 import org.displaytag.util.ReflectHelper;
21
22
23 /**
24  * Factory for TableDecorator or ColumnDecorator object.
25  * @author Fabrizio Giustina
26  * @version $Id$
27  */
28 public class DefaultDecoratorFactory implements DecoratorFactory
29 {
30
31     /**
32      * <p>
33      * If the user has specified a decorator, then this method takes care of creating the decorator (and checking to
34      * make sure it is a subclass of the TableDecorator object). If there are any problems loading the decorator then
35      * this will throw a DecoratorInstantiationException which will get propagated up to the page.
36      * </p>
37      * <p>
38      * Two different methods for loading a decorator are handled by this factory:
39      * </p>
40      * <ul>
41      * <li>First of all, an object with key <code>decoratorName</code> is searched in the page/request/session/scope</li>
42      * <li>If not found, assume <code>decoratorName</code> is the class name of the decorator and load it using
43      * reflection</li>
44      * </ul>
45      * @param decoratorName String full decorator class name
46      * @return instance of TableDecorator
47      * @throws DecoratorInstantiationException if unable to load specified TableDecorator
48      */
49     public TableDecorator loadTableDecorator(PageContext JavaDoc pageContext, String JavaDoc decoratorName)
50         throws DecoratorInstantiationException
51     {
52         if (StringUtils.isBlank(decoratorName))
53         {
54             return null;
55         }
56
57         // first check: is decoratorName an object in page/request/session/application scope?
58 Object JavaDoc decorator = pageContext.findAttribute(decoratorName);
59
60         // second check: if a decorator was not found assume decoratorName is the class name and load it using
61 // reflection
62 if (decorator == null)
63         {
64             try
65             {
66                 decorator = ReflectHelper.classForName(decoratorName).newInstance();
67             }
68             catch (ClassNotFoundException JavaDoc e)
69             {
70                 throw new DecoratorInstantiationException(DefaultDecoratorFactory.class, decoratorName, e);
71             }
72             catch (InstantiationException JavaDoc e)
73             {
74                 throw new DecoratorInstantiationException(DefaultDecoratorFactory.class, decoratorName, e);
75             }
76             catch (IllegalAccessException JavaDoc e)
77             {
78                 throw new DecoratorInstantiationException(DefaultDecoratorFactory.class, decoratorName, e);
79             }
80         }
81
82         if (decorator instanceof TableDecorator)
83         {
84             return (TableDecorator) decorator;
85         }
86         else
87         {
88             throw new DecoratorInstantiationException(
89                 DefaultDecoratorFactory.class,
90                 decoratorName,
91                 new ClassCastException JavaDoc(decorator.getClass().getName()));
92         }
93
94     }
95
96     /**
97      * <p>
98      * If the user has specified a column decorator, then this method takes care of creating the decorator (and checking
99      * to make sure it is a subclass of the DisplaytagColumnDecorator object). If there are any problems loading the
100      * decorator then this will throw a DecoratorInstantiationException which will get propagated up to the page.
101      * </p>
102      * <p>
103      * Two different methods for loading a decorator are handled by this factory:
104      * </p>
105      * <ul>
106      * <li>First of all, an object with key <code>decoratorName</code> is searched in the page/request/session/scope</li>
107      * <li>If not found, assume <code>decoratorName</code> is the class name of the decorator and load it using
108      * reflection</li>
109      * </ul>
110      * @param decoratorName String full decorator class name
111      * @return instance of DisplaytagColumnDecorator
112      * @throws DecoratorInstantiationException if unable to load ColumnDecorator
113      */
114     public DisplaytagColumnDecorator loadColumnDecorator(PageContext JavaDoc pageContext, String JavaDoc decoratorName)
115         throws DecoratorInstantiationException
116     {
117         if (StringUtils.isBlank(decoratorName))
118         {
119             return null;
120         }
121
122         // first check: is decoratorName an object in page/request/session/application scope?
123 Object JavaDoc decorator = pageContext.findAttribute(decoratorName);
124
125         // second check: if a decorator was not found assume decoratorName is the class name and load it using
126 // reflection
127 if (decorator == null)
128         {
129             try
130             {
131                 decorator = ReflectHelper.classForName(decoratorName).newInstance();
132             }
133             catch (ClassNotFoundException JavaDoc e)
134             {
135                 throw new DecoratorInstantiationException(DefaultDecoratorFactory.class, decoratorName, e);
136             }
137             catch (InstantiationException JavaDoc e)
138             {
139                 throw new DecoratorInstantiationException(DefaultDecoratorFactory.class, decoratorName, e);
140             }
141             catch (IllegalAccessException JavaDoc e)
142             {
143                 throw new DecoratorInstantiationException(DefaultDecoratorFactory.class, decoratorName, e);
144             }
145         }
146
147         if (decorator instanceof DisplaytagColumnDecorator)
148         {
149             return (DisplaytagColumnDecorator) decorator;
150         }
151         else if (decorator instanceof ColumnDecorator)
152         {
153             return new DeprecatedDecoratorWrapper((ColumnDecorator) decorator);
154         }
155         else
156         {
157             throw new DecoratorInstantiationException(
158                 DefaultDecoratorFactory.class,
159                 decoratorName,
160                 new ClassCastException JavaDoc(decorator.getClass().getName()));
161         }
162     }
163
164     /**
165      * Wrapper class for handling decorators implementing the deprecated ColumnDecorator interface as 1.1
166      * <code>DisplaytagColumnDecorator</code>s.
167      */
168     private static class DeprecatedDecoratorWrapper implements DisplaytagColumnDecorator
169     {
170
171         /**
172          * Wrapped 1.0 decorator.
173          */
174         private ColumnDecorator decorator;
175
176         /**
177          * Instantiates a new wrapper for old decorators.
178          * @param decorator ColumnDecorator instance
179          */
180         public DeprecatedDecoratorWrapper(ColumnDecorator decorator)
181         {
182             this.decorator = decorator;
183         }
184
185         /**
186          * @see org.displaytag.decorator.DisplaytagColumnDecorator#decorate(Object, PageContext, MediaTypeEnum)
187          * @deprecated
188          */
189         public Object JavaDoc decorate(Object JavaDoc columnValue, PageContext JavaDoc pageContext, MediaTypeEnum media)
190             throws DecoratorException
191         {
192             return decorator.decorate(columnValue);
193         }
194
195     }
196 }
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