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 }