001    /* MBeanAttributeInfo.java -- Information about an attribute of a bean.
002       Copyright (C) 2006 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    import java.lang.reflect.Method;
041    import java.lang.reflect.Type;
042    
043    /**
044     * Describes the attributes of a management bean.
045     * The information in this class is immutable as standard.
046     * Of course, subclasses may change this, but this
047     * behaviour is not recommended.
048     *
049     * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
050     * @since 1.5
051     */
052    public class MBeanAttributeInfo
053      extends MBeanFeatureInfo
054      implements Cloneable
055    {
056    
057      /**
058       * Compatible with JDK 1.6
059       */
060      private static final long serialVersionUID = 8644704819898565848L;
061    
062      /**
063       * The type of the attribute.
064       *
065       * @serial the attribute type.
066       */
067      private String attributeType;
068    
069      /**
070       * True if the attribute's value can be changed.
071       *
072       * @serial true if the value can be changed.
073       */
074      private boolean isWrite;
075    
076      /**
077       * True if the attribute's value can be read.
078       *
079       * @serial true if the value can be read.
080       */
081      private boolean isRead;
082    
083      /**
084       * True if the attribute is a boolean and thus
085       * has a isXXX accessor rather than a getXXX accessor.
086       *
087       * @serial true if the attribute has an isXXX accessor.
088       */
089      private boolean is;
090    
091      /**
092       * Constructs a new {@link MBeanAttributeInfo} using the specified
093       * name and description, with the given accessor and mutator
094       * methods.  A <code>null</code> value for the accessor method
095       * indicates that the value can not be read.  A <code>null</code>
096       * value for the mutator method indicates that the value can not be
097       * changed.
098       *
099       * @param name the name of the attribute.
100       * @param desc a description of the attribute.
101       * @param getter the accessor method, or <code>null</code> if the value
102       *               can not be read.
103       * @param setter the mutator method, or <code>null</code> if the value
104       *               can not be changed.
105       * @throws IntrospectionException if both the accessor and mutator method
106       *                                are <code>null</code>.
107       */
108      public MBeanAttributeInfo(String name, String desc,
109                                Method getter, Method setter)
110        throws IntrospectionException
111      {
112        super(name, desc);
113        if (getter == null && setter == null)
114          throw new IntrospectionException("Both the getter and setter methods can " +
115                                           "not be null.");
116        if (getter == null)
117          {
118            Type t = setter.getGenericParameterTypes()[0];
119            if (t instanceof Class)
120              attributeType = ((Class<?>) t).getName();
121            else
122              attributeType = t.toString();
123            isRead = false;
124            is = false;
125          }
126        else
127          {
128            Type t = getter.getGenericReturnType();
129            if (t instanceof Class)
130              attributeType = ((Class<?>) t).getName();
131            else
132              attributeType = t.toString();
133            isRead = true;
134            is = getter.getName().startsWith("is");
135          }
136        if (setter != null)
137          isWrite = true;
138      }
139    
140      /**
141       * Constructs a new {@link MBeanAttributeInfo} using the specified
142       * name, description and type with the given settings for the accessor
143       * and mutator methods.
144       *
145       * @param name the name of the attribute.
146       * @param type the type of the attribute, in the form of its class name.
147       * @param desc a description of the attribute.
148       * @param isReadable true if the attribute's value can be read.
149       * @param isWritable true if the attribute's value can be changed.
150       * @param isIs true if the attribute uses an accessor of the form isXXX.
151       * @throws IllegalArgumentException if the attribute is both unreadable
152       *                                  and unwritable.
153       */
154      public MBeanAttributeInfo(String name, String type, String desc,
155                                boolean isReadable, boolean isWritable,
156                                boolean isIs)
157      {
158        super(name, desc);
159        if (!isReadable && !isWritable)
160          throw new IllegalArgumentException("The attribute can not be both " +
161                                             "unreadable and unwritable.");
162        attributeType = type;
163        isRead = isReadable;
164        isWrite = isWritable;
165        is = isIs;
166      }
167    
168      /**
169       * Returns a clone of this instance.  The clone is created
170       * using just the method provided by {@link java.lang.Object}.
171       * Thus, the clone is just a shallow clone as returned by
172       * that method, and does not contain any deeper cloning based
173       * on the subject of this class.
174       *
175       * @return a clone of this instance.
176       * @see java.lang.Cloneable
177       */
178      public Object clone()
179      {
180        try
181          {
182            return super.clone();
183          }
184        catch (CloneNotSupportedException e)
185          {
186            /* This shouldn't happen; we implement Cloneable */
187            throw new IllegalStateException("clone() called on " +
188                                            "non-cloneable object.");
189          }
190      }
191    
192      /**
193       * Compares this feature with the supplied object.  This
194       * returns true iff the object is an instance of
195       * {@link MBeanAttributeInfo}, {@link Object#equals()}
196       * returns true for a comparison of both the name and
197       * description of this attribute  with that of the specified
198       * object (performed by the superclass), and the type and
199       * boolean flags of the two instances are equal.
200       *
201       * @param obj the object to compare.
202       * @return true if the object is a {@link MBeanAttributeInfo}
203       *         instance,
204       *         <code>name.equals(object.getName())</code>,
205       *         <code>description.equals(object.getDescription())</code>,
206       *         <code>attributeType.equals(object.getType())</code>,
207       *         <code>isRead == object.isReadable()</code>,
208       *         <code>isWrite == object.isWritable()</code>,
209       *         <code>is == object.isIs()</code>
210       */
211      public boolean equals(Object obj)
212      {
213        if (!(obj instanceof MBeanAttributeInfo))
214          return false;
215        if (!(super.equals(obj)))
216          return false;
217        MBeanAttributeInfo o = (MBeanAttributeInfo) obj;
218        return (attributeType.equals(o.getType()) &&
219                isRead == o.isReadable() &&
220                isWrite == o.isWritable() &&
221                is == o.isIs());
222      }
223    
224      /**
225       * Returns the type of this attribute, in the form of its class name.
226       *
227       * @return the type of this attribute.
228       */
229      public String getType()
230      {
231        return attributeType;
232      }
233    
234      /**
235       * Returns the hashcode of the attribute information as the sum of
236       * the hashcode of the superclass, the hashcode of the type,
237       * the hashcode of {@link #isReadable()}, twice the hashcode
238       * of {@link #isWritable()} and four times the hashcode
239       * of {@link #isIs()}.
240       *
241       * @return the hashcode of the attribute information.
242       */
243      public int hashCode()
244      {
245        return super.hashCode() + attributeType.hashCode()
246          + Boolean.valueOf(isRead).hashCode()
247          + (2 * Boolean.valueOf(isWrite).hashCode())
248          + (4 * Boolean.valueOf(is).hashCode());
249      }
250    
251      /**
252       * Returns true if the accessor method of this attribute
253       * is of the form <code>isXXX</code>.
254       *
255       * @return true if the accessor takes the form <code>isXXX</code>.
256       */
257      public boolean isIs()
258      {
259        return is;
260      }
261    
262      /**
263       * Returns true if value of this attribute can be read.
264       *
265       * @return true if the value of the attribute can be read.
266       */
267      public boolean isReadable()
268      {
269        return isRead;
270      }
271    
272      /**
273       * Returns true if the value of this attribute can be changed.
274       *
275       * @return true if the value of the attribute can be changed.
276       */
277      public boolean isWritable()
278      {
279        return isWrite;
280      }
281    
282      /**
283       * <p>
284       * Returns a textual representation of this instance.  This
285       * is constructed using the class name
286       * (<code>javax.management.MBeanAttributeInfo</code>),
287       * the name, description and type of the attribute and the
288       * current settings of the {@link #isReadable()},
289       * {@link #isWritable()} and {@link #isIs()} properties.
290       * </p>
291       * <p>
292       * As instances of this class are immutable, the return value
293       * is computed just once for each instance and reused
294       * throughout its life.
295       * </p>
296       *
297       * @return a @link{java.lang.String} instance representing
298       *         the instance in textual form.
299       */
300      public String toString()
301      {
302        if (string == null)
303          {
304            super.toString();
305            string = string.substring(0, string.length() - 1)
306              + ",type=" + attributeType
307              + ",isReadable=" + (isRead ? "yes" : "no")
308              + ",isWritable=" + (isWrite ? "yes" : "no")
309              + ",isIs=" + (is ? "yes" : "no")
310              + "]";
311          }
312        return string;
313      }
314    
315    }