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Java > Open Source Codes > org > apache > commons > betwixt > expression > DynaBeanExpression


1 /*
2  * Copyright 2001-2004 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
17 package org.apache.commons.betwixt.expression;
18
19 import org.apache.commons.beanutils.DynaBean;
20
21 /**
22  * An Expression that gets a property value from a DynaBean.
23  *
24  * @see org.apache.commons.beanutils.DynaBean
25  *
26  * @author Michael Becke
27  * @since 0.5
28  */
29 public class DynaBeanExpression implements Expression {
30
31     /** The name of the DynaBean property to get */
32     private String JavaDoc propertyName;
33
34     /**
35      * Crates a new DynaBeanExpression.
36      */
37     public DynaBeanExpression() {
38         super();
39     }
40
41     /**
42      * Crates a new DynaBeanExpression.
43      *
44      * @param propertyName the name of the DynaBean property to use
45      */
46     public DynaBeanExpression(String JavaDoc propertyName) {
47         super();
48         setPropertyName(propertyName);
49     }
50
51     /**
52      * Returns the value of a DynaBean property from the bean stored in
53      * the Context. Returns <code>null</code> if no DynaBean is stored
54      * in the Context or if the propertyName has not been set.
55      *
56      * @param context the content containing the DynaBean
57      *
58      * @return the DynaBean property value or <code>null</code>
59      */
60     public Object JavaDoc evaluate(Context context) {
61         
62         if (context.getBean() instanceof DynaBean && propertyName != null) {
63             return ((DynaBean)context.getBean()).get(propertyName);
64         } else {
65             return null;
66         }
67     }
68
69     /**
70      * Do nothing.
71      * @see Expression#update
72      */
73     public void update(Context context, String JavaDoc newValue) {
74         // do nothing
75 }
76
77     /**
78      * Gets the name of the property to get from the DynaBean.
79      * @return the name of the property that this expression reads
80      */
81     public String JavaDoc getPropertyName() {
82         return propertyName;
83     }
84
85     /**
86      * Sets the name of the property to get from the DynaBean.
87      * @param propertyName the property that this expression reads, not null
88      */
89     public void setPropertyName(String JavaDoc propertyName) {
90         if (propertyName == null) {
91             throw new IllegalArgumentException JavaDoc("propertyName is null");
92         }
93         this.propertyName = propertyName;
94     }
95
96 }
97
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