1 /*
2 * $Header: /home/cvs/jakarta-commons/betwixt/src/java/org/apache/commons/betwixt/expression/Context.java,v 1.1 2002/06/10 17:53:33 jstrachan Exp $
3 * $Revision: 1.1 $
4 * $Date: 2002/06/10 17:53:33 $
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 * $Id: Context.java,v 1.1 2002/06/10 17:53:33 jstrachan Exp $
60 */
61 package org.apache.commons.betwixt.expression;
62
63 import java.util.HashMap;
64 import java.util.Map;
65
66 import org.apache.commons.logging.Log;
67 import org.apache.commons.logging.LogFactory;
68
69 /*** <p><code>Context</code> describes the context used to evaluate
70 * bean expressions.
71 * This is mostly a bean together with a number of context variables.
72 * Context variables are named objects.
73 * In other words,
74 * a context variable associates an object with a string.</p>
75 *
76 * <p> Logging during expression evaluation is done through the logging
77 * instance held by this class.
78 * The object initiating the evaluation should control this logging
79 * and so passing a <code>Log</code> instance is enforced by the constructors.</p>
80 *
81 * <p><code>Context</code> is a natural place to include shared evaluation code.
82 * One of the problems that you get with object graphs is that they can be cyclic.
83 * Xml cannot (directly) include cycles.
84 * Therefore <code>betwixt</code> needs to find and deal properly with cycles.
85 * The algorithm used is to check the parentage of a new child.
86 * If the child is a parent then that operation fails. </p>
87 *
88 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
89 * @version $Revision: 1.1 $
90 */
91 public class Context {
92
93 /*** Evaluate this bean */
94 private Object bean;
95 /*** Variables map */
96 private Map variables = new HashMap();
97 /*** Logging uses commons-logging <code>Log</code> named <code>org.apache.commons.betwixt</code> */
98 private Log log;
99
100 /*** Construct context with default log */
101 public Context() {
102 this.log = LogFactory.getLog( getClass() );
103 }
104
105 /*** Convenience constructor sets evaluted bean and log.
106 *
107 * @param bean evaluate expressions against this bean
108 * @param log log to this logger
109 */
110 public Context(Object bean, Log log) {
111 this.bean = bean;
112 this.log = log;
113 }
114
115 /*** Convenience constructor sets evaluted bean, context variables and log.
116 *
117 * @param bean evaluate expressions against this bean
118 * @param variables context variables
119 * @param log log to this logger
120 */
121 public Context(Object bean, Map variables, Log log) {
122 this.bean = bean;
123 this.variables = variables;
124 this.log = log;
125 }
126
127 /*** Returns a new child context with the given bean but the same log and variables.
128 *
129 * @param newBean create a child context for this bean
130 */
131 public Context newContext(Object newBean) {
132 return new Context(newBean, variables, log);
133 }
134
135 /*** Returns the current bean.
136 */
137 public Object getBean() {
138 return bean;
139 }
140
141 /*** Set the current bean.
142 */
143 public void setBean(Object bean) {
144 this.bean = bean;
145 }
146
147 /*** Get context variables.
148 */
149 public Map getVariables() {
150 return variables;
151 }
152
153 /*** Set context variables.
154 */
155 public void setVariables(Map variables) {
156 this.variables = variables;
157 }
158
159 /*** Get the value of a particular context variable.
160 */
161 public Object getVariable(String name) {
162 return variables.get( name );
163 }
164
165 /*** Set the value of a particular context variable.
166 */
167 public void setVariable(String name, Object value) {
168 variables.put( name, value );
169 }
170
171 /*** Get the current log.
172 */
173 public Log getLog() {
174 return log;
175 }
176
177 /*** Set the logger used to log (Doh!).
178 */
179 public void setLog() {
180 this.log = log;
181 }
182 }
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