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}