001/* MBeanAttributeInfo.java -- Information about an attribute of a bean.
002   Copyright (C) 2006 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
040import java.lang.reflect.Method;
041import 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 */
052public 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}