001/* AttributeValueExp.java -- Represents attributes to be passed to queries. 002 Copyright (C) 2007 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038package javax.management; 039 040/** 041 * Represents an attribute value being used as an argument 042 * to a relational constraint. 043 * 044 * @author Andrew John Hughes (gnu_andrew@member.fsf.org) 045 * @since 1.5 046 */ 047public class AttributeValueExp 048 implements ValueExp 049{ 050 051 /** 052 * Compatible with JDK 1.5 053 */ 054 private static final long serialVersionUID = -7768025046539163385L; 055 056 /** 057 * The name of the attribute. 058 */ 059 private String attr; 060 061 /** 062 * Constructs a new {@link AttributeValueExp}. 063 * 064 * @deprecated An instance created with a <code>null</code> 065 * attribute name can not be used in a query. 066 */ 067 @Deprecated public AttributeValueExp() 068 { 069 } 070 071 /** 072 * Constructs a new {@link AttributeValueExp} using the 073 * specified attribute. 074 * 075 * @param attr the name of the attribute whose value 076 * will be used for this expression. 077 */ 078 public AttributeValueExp(String attr) 079 { 080 this.attr = attr; 081 } 082 083 /** 084 * Applies the {@link AttributeValueExp} to the specified 085 * management bean by obtaining the attribute value from 086 * the {@link MBeanServer} and using it to create a 087 * {@link StringValueExp}. 088 * 089 * @param name the {@link ObjectName} of the bean to obtain 090 * the value from. 091 * @return a {@link StringValueExp} containing the result. 092 * @throws BadStringOperationException if an invalid string 093 * operation is used by 094 * the value expression. 095 * @throws BadBinaryOpValueExpException if an invalid expression 096 * is used by the value expression. 097 * @throws BadAttributeValueExpException if an invalid attribute 098 * is used by the value expression. 099 * @throws InvalidApplicationException if the value expression is applied 100 * to the wrong type of bean. 101 */ 102 public ValueExp apply(ObjectName name) 103 throws BadStringOperationException, BadBinaryOpValueExpException, 104 BadAttributeValueExpException, InvalidApplicationException 105 { 106 Object val = getAttribute(name); 107 if (val == null || !(val instanceof String)) 108 throw new BadAttributeValueExpException(val); 109 return new StringValueExp((String) val); 110 } 111 112 /** 113 * Returns the value of the attribute by calling the 114 * {@link MBeanServer#getAttribute(ObjectName)} method of 115 * the server returned by {@link QueryEval#getMBeanServer()}. 116 * If an exception occurs, <code>null</code> is returned. 117 * 118 * @param name the {@link ObjectName} of the bean to obtain 119 * the value from. 120 * @return a {@link StringValueExp} containing the result. 121 */ 122 protected Object getAttribute(ObjectName name) 123 { 124 try 125 { 126 return QueryEval.getMBeanServer().getAttribute(name, attr); 127 } 128 catch (NullPointerException e) 129 { 130 return null; 131 } 132 catch (MBeanException e) 133 { 134 return null; 135 } 136 catch (AttributeNotFoundException e) 137 { 138 return null; 139 } 140 catch (InstanceNotFoundException e) 141 { 142 return null; 143 } 144 catch (ReflectionException e) 145 { 146 return null; 147 } 148 } 149 150 /** 151 * Returns the attribute name. 152 * 153 * @return the attribute name. 154 */ 155 public String getAttributeName() 156 { 157 return attr; 158 } 159 160 /** 161 * Sets the {@link MBeanServer} on which the query 162 * will be performed. 163 * 164 * @param server the new server. 165 */ 166 public void setMBeanServer(MBeanServer server) 167 { 168 /* This seems to do nothing any more */ 169 } 170 171 /** 172 * Returns the attribute name, quoted. 173 * 174 * @return the quoted attribute name. 175 */ 176 public String toString() 177 { 178 return "'" + attr + "'"; 179 } 180 181}