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1 /* 2 * $Header: /home/cvs/jakarta-commons/betwixt/src/java/org/apache/commons/betwixt/expression/Context.java,v 1.4 2003/01/12 13:52:03 rdonkin Exp $ 3 * $Revision: 1.4 $ 4 * $Date: 2003/01/12 13:52:03 $ 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 1.4 2003/01/12 13:52:03 rdonkin 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: 1.4 $ 90 */ 91 public class Context { 92 93 /*** Evaluate this bean */ 94 private Object bean; 95 /*** Variables map */ 96 private Map variables = new HashMap(); 97 /*** 98 * Logging uses commons-logging <code>Log</code> 99 * named <code>org.apache.commons.betwixt</code> 100 */ 101 private Log log; 102 103 /*** Construct context with default log */ 104 public Context() { 105 this.log = LogFactory.getLog( getClass() ); 106 } 107 108 /*** Convenience constructor sets evaluted bean and log. 109 * 110 * @param bean evaluate expressions against this bean 111 * @param log log to this logger 112 */ 113 public Context(Object bean, Log log) { 114 this.bean = bean; 115 this.log = log; 116 } 117 118 /*** Convenience constructor sets evaluted bean, context variables and log. 119 * 120 * @param bean evaluate expressions against this bean 121 * @param variables context variables 122 * @param log log to this logger 123 */ 124 public Context(Object bean, Map variables, Log log) { 125 this.bean = bean; 126 this.variables = variables; 127 this.log = log; 128 } 129 130 /*** Returns a new child context with the given bean but the same log and variables. 131 * 132 * @param newBean create a child context for this bean 133 * @return new Context with new bean but shared variables 134 */ 135 public Context newContext(Object newBean) { 136 return new Context(newBean, variables, log); 137 } 138 139 /*** 140 * Gets the current bean. 141 * @return the bean against which expressions are evaluated 142 */ 143 public Object getBean() { 144 return bean; 145 } 146 147 /*** 148 * Set the current bean. 149 * @param bean the Object against which expressions will be evaluated 150 */ 151 public void setBean(Object bean) { 152 this.bean = bean; 153 } 154 155 /*** 156 * Gets context variables. 157 * @return map containing variable values keyed by variable name 158 */ 159 public Map getVariables() { 160 return variables; 161 } 162 163 /*** 164 * Sets context variables. 165 * @param variables map containing variable values indexed by varibable name Strings 166 */ 167 public void setVariables(Map variables) { 168 this.variables = variables; 169 } 170 171 /*** 172 * Gets the value of a particular context variable. 173 * @param name the name of the variable whose value is to be returned 174 * @return the variable value or null if the variable isn't set 175 */ 176 public Object getVariable(String name) { 177 return variables.get( name ); 178 } 179 180 /*** 181 * Sets the value of a particular context variable. 182 * @param name the name of the variable 183 * @param value the value of the variable 184 */ 185 public void setVariable(String name, Object value) { 186 variables.put( name, value ); 187 } 188 189 /*** 190 * Gets the current log. 191 * 192 * @return the implementation to which this class logs 193 */ 194 public Log getLog() { 195 return log; 196 } 197 198 /*** 199 * Set the log implementation to which this class logs 200 * 201 * @param log the implemetation that this class should log to 202 */ 203 public void setLog(Log log) { 204 this.log = log; 205 } 206 }

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