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    }