001 /* AttributeValueExp.java -- Represents attributes to be passed to queries. 002 Copyright (C) 2007 Free Software Foundation, Inc. 003 004 This file is part of GNU Classpath. 005 006 GNU Classpath is free software; you can redistribute it and/or modify 007 it under the terms of the GNU General Public License as published by 008 the Free Software Foundation; either version 2, or (at your option) 009 any later version. 010 011 GNU Classpath is distributed in the hope that it will be useful, but 012 WITHOUT ANY WARRANTY; without even the implied warranty of 013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014 General Public License for more details. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 019 02110-1301 USA. 020 021 Linking this library statically or dynamically with other modules is 022 making a combined work based on this library. Thus, the terms and 023 conditions of the GNU General Public License cover the whole 024 combination. 025 026 As a special exception, the copyright holders of this library give you 027 permission to link this library with independent modules to produce an 028 executable, regardless of the license terms of these independent 029 modules, and to copy and distribute the resulting executable under 030 terms of your choice, provided that you also meet, for each linked 031 independent module, the terms and conditions of the license of that 032 module. An independent module is a module which is not derived from 033 or based on this library. If you modify this library, you may extend 034 this exception to your version of the library, but you are not 035 obligated to do so. If you do not wish to do so, delete this 036 exception statement from your version. */ 037 038 package 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 */ 047 public 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 }