libjava/classpath/javax/management/MBeanAttributeInfo.java

   1 /* MBeanAttributeInfo.java -- Information about an attribute of a bean.
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package javax.management;
  39
  40 import java.lang.reflect.Method;
  41 import java.lang.reflect.Type;
  42
  43 /**
  44  * Describes the attributes of a management bean.
  45  * The information in this class is immutable as standard.
  46  * Of course, subclasses may change this, but this
  47  * behaviour is not recommended.
  48  *
  49  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  50  * @since 1.5
  51  */
  52 public class MBeanAttributeInfo
  53   extends MBeanFeatureInfo
  54   implements Cloneable
  55 {
  56
  57   /**
  58    * Compatible with JDK 1.6
  59    */
  60   private static final long serialVersionUID = 8644704819898565848L;
  61
  62   /**
  63    * The type of the attribute.
  64    *
  65    * @serial the attribute type.
  66    */
  67   private String attributeType;
  68
  69   /**
  70    * True if the attribute's value can be changed.
  71    *
  72    * @serial true if the value can be changed.
  73    */
  74   private boolean isWrite;
  75
  76   /**
  77    * True if the attribute's value can be read.
  78    *
  79    * @serial true if the value can be read.
  80    */
  81   private boolean isRead;
  82
  83   /**
  84    * True if the attribute is a boolean and thus
  85    * has a isXXX accessor rather than a getXXX accessor.
  86    *
  87    * @serial true if the attribute has an isXXX accessor.
  88    */
  89   private boolean is;
  90
  91   /**
  92    * Constructs a new {@link MBeanAttributeInfo} using the specified
  93    * name and description, with the given accessor and mutator
  94    * methods.  A <code>null</code> value for the accessor method
  95    * indicates that the value can not be read.  A <code>null</code>
  96    * value for the mutator method indicates that the value can not be
  97    * changed.
  98    *
  99    * @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 }