libjava/classpath/javax/management/MBeanServerInvocationHandler.java

   1 /* MBeanServerInvocationHandler.java -- Provides a proxy for a bean.
   2    Copyright (C) 2007 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 gnu.javax.management.Translator;
  41
  42 import java.lang.reflect.InvocationHandler;
  43 import java.lang.reflect.Method;
  44 import java.lang.reflect.Proxy;
  45
  46 /**
  47  * <p>
  48  * Provides a proxy for a management bean.  The methods
  49  * of the given interface are fulfilled by redirecting the
  50  * calls over an {@link MBeanServerConnection} to the bean
  51  * specified by the supplied {@link ObjectName}.
  52  * </p>
  53  * <p>
  54  * The {@link java.lang.reflect.InvocationHandler} also makes
  55  * provision for {@link MXBean}s by providing type conversion
  56  * according to the rules defined for these beans.  The input
  57  * parameters are converted to their equivalent open type before
  58  * calling the method, and then the return value is converted
  59  * back from its open type to the appropriate Java type.  For
  60  * example, a method that takes an {@link Enum} as input and
  61  * returns a {@link java.util.List} will have the input value
  62  * converted from an {@link Enum} to a {@link String}, while
  63  * the return value will be converted from its return type
  64  * (an appropriately typed array) to a {@link java.util.List}.
  65  * </p>
  66  * <p>
  67  * The proxy has special cases for the {@link Object#equals(Object)},
  68  * {@link Object#hashCode()} and {@link Object#toString()} methods.
  69  * Unless they are specified explictly by the interface, the
  70  * following behaviour is provided for these methods by the proxy:
  71  * </p>
  72  * <ul>
  73  * <li><code>equals(Object)</code> returns true if the other object
  74  * is an {@link MBeanServerInvocationHandler} with the same
  75  * {@link MBeanServerConnection} and {@link ObjectName}.  If an
  76  * interface class was specified on construction for one of the
  77  * proxies, then the same class must have also been specified
  78  * for the other.</li>
  79  * <li><code>hashCode()</code> returns the same value for
  80  * equivalent proxies.</li>
  81  * <li><code>toString()</code> returns a textual representation
  82  * of the proxy.</li>
  83  * </ul>
  84  *
  85  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  86  * @since 1.5
  87  */
  88 public class MBeanServerInvocationHandler
  89   implements InvocationHandler
  90 {
  91
  92   /**
  93    * The connection used to make the calls.
  94    */
  95   private MBeanServerConnection conn;
  96
  97   /**
  98    * The name of the bean to perform operations on.
  99    */
 100   private ObjectName name;
 101
 102   /**
 103    * True if this proxy is for an {@link MXBean}.
 104    */
 105   private boolean mxBean;
 106
 107   /**
 108    * The interface class associated with the bean.
 109    */
 110   private Class<?> iface;
 111
 112   /**
 113    * Constructs a new {@link MBeanServerInvocationHandler}
 114    * which forwards methods to the supplied bean via the
 115    * given {@link MBeanServerConnection}.  This constructor
 116    * is used in preference to
 117    * {@link JMX#newMBeanProxy(MBeanServerConnection, ObjectName,
 118    * Class<T>)} if you wish to make your own call to
 119    * {@link java.lang.reflect.Proxy#newInstance(ClassLoader,
 120    * Class[], java.lang.reflect.InvocationHandler)} with
 121    * a different {@link ClassLoader}.  Calling this constructor
 122    * is equivalent to <code>MBeanServerInvocationHandler(conn,
 123    * name, false)</code>.  The other constructor should be used
 124    * instead if the bean being proxied is an {@link MXBean}.
 125    *
 126    * @param conn the connection through which methods will
 127    *             be forwarded to the bean.
 128    * @param name the name of the bean to use to provide the
 129    *             actual calls.
 130    */
 131   public MBeanServerInvocationHandler(MBeanServerConnection conn,
 132                                       ObjectName name)
 133   {
 134     this(conn, name, false);
 135   }
 136
 137   /**
 138    * Constructs a new {@link MBeanServerInvocationHandler}
 139    * which forwards methods to the supplied bean via the
 140    * given {@link MBeanServerConnection}.  This constructor
 141    * is used in preference to
 142    * {@link JMX#newMBeanProxy(MBeanServerConnection, ObjectName,
 143    * Class<T>)} if you wish to make your own call to
 144    * {@link java.lang.reflect.Proxy#newInstance(ClassLoader,
 145    * Class[], java.lang.reflect.InvocationHandler)} with
 146    * a different {@link ClassLoader}.
 147    *
 148    * @param conn the connection through which methods will
 149    *             be forwarded to the bean.
 150    * @param name the name of the bean to use to provide the
 151    *             actual calls.
 152    * @param mxBean true if the bean being proxied is an
 153    *               {@link MXBean}.
 154    * @since 1.6
 155    */
 156   public MBeanServerInvocationHandler(MBeanServerConnection conn,
 157                                       ObjectName name, boolean mxBean)
 158   {
 159     this.conn = conn;
 160     this.name = name;
 161     this.mxBean = mxBean;
 162   }
 163
 164   /**
 165    * Returns the connection through which the calls to the bean
 166    * will be made.
 167    *
 168    * @return the connection being used to forward the calls to
 169    *         the bean.
 170    * @since 1.6
 171    */
 172   public MBeanServerConnection getMBeanServerConnection()
 173   {
 174     return conn;
 175   }
 176
 177   /**
 178    * Returns the name of the bean to which method calls are made.
 179    *
 180    * @return the bean which provides the actual method calls.
 181    * @since 1.6
 182    */
 183   public ObjectName getObjectName()
 184   {
 185     return name;
 186   }
 187
 188   /**
 189    * Called by the proxy class whenever a method is called.  The method
 190    * is emulated by retrieving an attribute from, setting an attribute on
 191    * or invoking a method on the server connection as required.  Translation
 192    * between the Java data types supplied as arguments to the open types used
 193    * by the bean is provided, as well as translation of the return value back
 194    * in to the appropriate Java type if the bean is an {@link MXBean}.
 195    *
 196    * @param proxy the proxy on which the method was called.
 197    * @param method the method which was called.
 198    * @param args the arguments supplied to the method.
 199    * @return the return value from the method.
 200    * @throws Throwable if an exception is thrown in performing the
 201    *                   method emulation.
 202    */
 203   public Object invoke(Object proxy, Method method, Object[] args)
 204     throws Throwable
 205   {
 206     String mName = method.getName();
 207     Class<?> proxyClass = proxy.getClass();
 208     if (mName.equals("toString"))
 209       {
 210         if (inInterface(mName, proxyClass))
 211           return conn.invoke(name,mName,null,null);
 212         else
 213           return proxyClass.getName() + "[name=" + name
 214             + ", conn=" + conn + "]";
 215       }
 216     if (mName.equals("hashCode"))
 217       {
 218         if (inInterface(mName, proxyClass))
 219           return conn.invoke(name,mName,null,null);
 220         else
 221           return conn.hashCode() + name.hashCode()
 222             + (iface == null ? 0 : iface.hashCode());
 223       }
 224     if (mName.equals("equals"))
 225       {
 226         if (inInterface(mName, proxyClass, Object.class))
 227           return conn.invoke(name,mName,new Object[]{args[0]},
 228                              new String[]{"java.lang.Object"});
 229         else
 230           {
 231             if (args[0].getClass() != proxy.getClass())
 232               return false;
 233             InvocationHandler ih = Proxy.getInvocationHandler(args[0]);
 234             if (ih instanceof MBeanServerInvocationHandler)
 235               {
 236                 MBeanServerInvocationHandler h =
 237                   (MBeanServerInvocationHandler) ih;
 238                 return conn.equals(h.getMBeanServerConnection())
 239                   && name.equals(h.getObjectName())
 240                   && (iface == null ? h.iface == null
 241                       : iface.equals(h.iface));
 242               }
 243             return false;
 244           }
 245       }
 246     if (NotificationEmitter.class.isAssignableFrom(proxyClass))
 247       {
 248         if (mName.equals("addNotificationListener"))
 249           {
 250             conn.addNotificationListener(name,
 251                                          (NotificationListener) args[0],
 252                                          (NotificationFilter) args[1],
 253                                          args[2]);
 254             return null;
 255           }
 256         if (mName.equals("getNotificationInfo"))
 257           return conn.getMBeanInfo(name).getNotifications();
 258         if (mName.equals("removeNotificationListener"))
 259           {
 260             if (args.length == 1)
 261               conn.removeNotificationListener(name,
 262                                               (NotificationListener)
 263                                               args[0]);
 264             else
 265               conn.removeNotificationListener(name,
 266                                               (NotificationListener)
 267                                               args[0],
 268                                               (NotificationFilter)
 269                                               args[1], args[2]);
 270             return null;
 271           }
 272       }
 273     String[] sigs;
 274     if (args == null)
 275       sigs = null;
 276     else
 277       {
 278         sigs = new String[args.length];
 279         for (int a = 0; a < args.length; ++a)
 280           sigs[a] = args[a].getClass().getName();
 281       }
 282     String attrib = null;
 283     if (mName.startsWith("get"))
 284       attrib = mName.substring(3);
 285     else if (mName.startsWith("is"))
 286       attrib = mName.substring(2);
 287     if (attrib != null)
 288       {
 289         Object val = conn.getAttribute(name, attrib);
 290         if (mxBean)
 291           return Translator.toJava(val, method);
 292         else
 293           return val;
 294       }
 295     else if (mName.startsWith("set"))
 296       {
 297         Object arg;
 298         if (mxBean)
 299           arg = Translator.fromJava(args, method)[0];
 300         else
 301           arg = args[0];
 302         conn.setAttribute(name, new Attribute(mName.substring(3), arg));
 303         return null;
 304       }
 305     if (mxBean)
 306       return Translator.toJava(conn.invoke(name, mName,
 307                                            Translator.fromJava(args,method),
 308                                            sigs), method);
 309     else
 310       return conn.invoke(name, mName, args, sigs);
 311   }
 312
 313   /**
 314    * Returns true if this is a proxy for an {@link MXBean}
 315    * and conversions must be applied to input parameters
 316    * and return types, according to the rules for such beans.
 317    *
 318    * @return true if this is a proxy for an {@link MXBean}.
 319    * @since 1.6
 320    */
 321   public boolean isMXBean()
 322   {
 323     return mxBean;
 324   }
 325
 326   /**
 327    * <p>
 328    * Returns a proxy for the specified bean.  A proxy object is created
 329    * using <code>Proxy.newProxyInstance(iface.getClassLoader(),
 330    * new Class[] { iface }, handler)</code>.  The
 331    * {@link javax.management.NotificationEmitter} class is included as the
 332    * second element of the array if <code>broadcaster</code> is true.
 333    * <code>handler</code> refers to the invocation handler which forwards
 334    * calls to the connection, which is created by a call to
 335    * <code>new MBeanServerInvocationHandler(conn, name)</code>.
 336    * </p>
 337    * <p>
 338    * <strong>Note</strong>: use of the proxy may result in
 339    * {@link java.io.IOException}s from the underlying
 340    * {@link MBeanServerConnection}.
 341    * As of 1.6, the use of {@link JMX#newMBeanProxy(MBeanServerConnection,
 342    * ObjectName,Class)} and {@link JMX#newMBeanProxy(MBeanServerConnection,
 343    * ObjectName,Class,boolean)} is preferred.
 344    * </p>
 345    *
 346    * @param conn the server connection to use to access the bean.
 347    * @param name the {@link javax.management.ObjectName} of the
 348    *             bean to provide a proxy for.
 349    * @param iface the interface for the bean being proxied.
 350    * @param broadcaster true if the proxy should implement
 351    *                    {@link NotificationEmitter}.
 352    * @return a proxy for the specified bean.
 353    * @see JMX#newMBeanProxy(MBeanServerConnection,ObjectName,Class)
 354    */
 355   // Suppress warnings as we know an instance of T will be returned.
 356   @SuppressWarnings("unchecked")
 357   public static <T> T newProxyInstance(MBeanServerConnection conn,
 358                                        ObjectName name, Class<T> iface,
 359                                        boolean broadcaster)
 360   {
 361     if (broadcaster)
 362       return (T) Proxy.newProxyInstance(iface.getClassLoader(),
 363                                         new Class[] { iface,
 364                                                       NotificationEmitter.class },
 365                                         new MBeanServerInvocationHandler(conn,name));
 366     else
 367       return (T) Proxy.newProxyInstance(iface.getClassLoader(),
 368                                         new Class[] { iface },
 369                                         new MBeanServerInvocationHandler(conn,name));
 370   }
 371
 372   /**
 373    * Returns true if the specified method is specified
 374    * by one of the proxy's interfaces.
 375    *
 376    * @param name the name of the method to search for.
 377    * @param proxyClass the class of the proxy.
 378    * @param args the arguments to the method.
 379    * @return true if one of the interfaces specifies the
 380    *         given method.
 381    */
 382   private boolean inInterface(String name, Class<?> proxyClass,
 383                               Class<?>... args)
 384   {
 385     for (Class<?> iface : proxyClass.getInterfaces())
 386       {
 387         try
 388           {
 389             iface.getMethod(name, args);
 390             return true;
 391           }
 392         catch (NoSuchMethodException e)
 393           {
 394             /* Ignored; this interface doesn't specify
 395                the method. */
 396           }
 397       }
 398     return false;
 399   }
 400
 401 }