1 /*
2 * $Header: /home/cvs/jakarta-commons/betwixt/src/java/org/apache/commons/betwixt/expression/MethodExpression.java,v 1.2 2002/07/01 18:56:26 rdonkin Exp $
3 * $Revision: 1.2 $
4 * $Date: 2002/07/01 18:56:26 $
5 *
6 * ====================================================================
7 *
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 1999-2002 The Apache Software Foundation. All rights
11 * reserved.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution, if
26 * any, must include the following acknowlegement:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowlegement may appear in the software itself,
30 * if and wherever such third-party acknowlegements normally appear.
31 *
32 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
33 * Foundation" must not be used to endorse or promote products derived
34 * from this software without prior written permission. For written
35 * permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache"
38 * nor may "Apache" appear in their names without prior written
39 * permission of the Apache Group.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>;.
59 *
60 * $Id: MethodExpression.java,v 1.2 2002/07/01 18:56:26 rdonkin Exp $
61 */
62 package org.apache.commons.betwixt.expression;
63
64 import java.lang.reflect.Method;
65
66 /*** <p><code>MethodExpression</code> evaluates a method on the current bean context.</p>
67 *
68 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
69 * @version $Revision: 1.2 $
70 */
71 public class MethodExpression implements Expression {
72
73 /*** null arguments */
74 protected static Object[] NULL_ARGUMENTS;
75 protected static Class[] NULL_CLASSES;
76
77 /*** The method to call on the bean */
78 private Method method;
79
80 /*** Base constructor */
81 public MethodExpression() {
82 }
83
84 /*** Convenience constructor sets method property */
85 public MethodExpression(Method method) {
86 this.method = method;
87 }
88
89 /*** Evaluate by calling the read method on the current bean */
90 public Object evaluate(Context context) {
91 Object bean = context.getBean();
92 if ( bean != null ) {
93 Object[] arguments = getArguments();
94 try {
95 return method.invoke( bean, arguments );
96 }
97 catch (IllegalAccessException e) {
98 // lets try use another method with the same name
99 try {
100 Class type = bean.getClass();
101 Method alternate = findAlternateMethod( type, method );
102 if ( alternate != null ) {
103 return alternate.invoke( bean, arguments );
104 }
105 }
106 catch (Exception e2) {
107 handleException(context, e2);
108 }
109 }
110 catch (Exception e) {
111 handleException(context, e);
112 }
113 }
114 return null;
115 }
116
117 public void update(Context context, String newValue) {
118 // do nothing
119 }
120
121 /*** Gets the constant value of this expression */
122 public Method getMethod() {
123 return method;
124 }
125
126 /*** Sets the constant value of this expression */
127 public void setMethod(Method method) {
128 this.method = method;
129 }
130
131 // Implementation methods
132 //-------------------------------------------------------------------------
133
134 /*** Allows derived objects to create arguments for the method call */
135 protected Object[] getArguments() {
136 return NULL_ARGUMENTS;
137 }
138
139 /*** Tries to find an alternate method for the given type using interfaces
140 * which gets around the problem of inner classes,
141 * such as on Map.Entry implementations.
142 */
143 protected Method findAlternateMethod(
144 Class type,
145 Method method )
146 throws
147 NoSuchMethodException {
148 Class[] interfaces = type.getInterfaces();
149 if ( interfaces != null ) {
150 String name = method.getName();
151 for ( int i = 0, size = interfaces.length; i < size; i++ ) {
152 Class otherType = interfaces[i];
153 Method alternate = otherType.getMethod( name, NULL_CLASSES );
154 if ( alternate != null && alternate != method ) {
155 return alternate;
156 }
157 }
158 }
159 return null;
160 }
161
162 /***
163 * <p> Log error to context's logger. </p>
164 *
165 * <p> Allows derived objects to handle exceptions differently. </p>
166 */
167 protected void handleException(Context context, Exception e) {
168 // use the context's logger to log the problem
169 context.getLog().error("[MethodExpression] Cannot evaluate expression", e);
170 }
171
172 public String toString() {
173 return "MethodExpression [method=" + method + "]";
174 }
175 }
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