mirror of git://gcc.gnu.org/git/gcc.git
402 lines
14 KiB
Java
402 lines
14 KiB
Java
/* MBeanServerInvocationHandler.java -- Provides a proxy for a bean.
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Copyright (C) 2007 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package javax.management;
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import gnu.javax.management.Translator;
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import java.lang.reflect.InvocationHandler;
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import java.lang.reflect.Method;
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import java.lang.reflect.Proxy;
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/**
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* <p>
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* Provides a proxy for a management bean. The methods
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* of the given interface are fulfilled by redirecting the
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* calls over an {@link MBeanServerConnection} to the bean
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* specified by the supplied {@link ObjectName}.
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* </p>
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* <p>
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* The {@link java.lang.reflect.InvocationHandler} also makes
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* provision for {@link MXBean}s by providing type conversion
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* according to the rules defined for these beans. The input
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* parameters are converted to their equivalent open type before
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* calling the method, and then the return value is converted
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* back from its open type to the appropriate Java type. For
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* example, a method that takes an {@link Enum} as input and
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* returns a {@link java.util.List} will have the input value
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* converted from an {@link Enum} to a {@link String}, while
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* the return value will be converted from its return type
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* (an appropriately typed array) to a {@link java.util.List}.
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* </p>
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* <p>
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* The proxy has special cases for the {@link Object#equals(Object)},
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* {@link Object#hashCode()} and {@link Object#toString()} methods.
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* Unless they are specified explictly by the interface, the
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* following behaviour is provided for these methods by the proxy:
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* </p>
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* <ul>
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* <li><code>equals(Object)</code> returns true if the other object
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* is an {@link MBeanServerInvocationHandler} with the same
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* {@link MBeanServerConnection} and {@link ObjectName}. If an
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* interface class was specified on construction for one of the
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* proxies, then the same class must have also been specified
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* for the other.</li>
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* <li><code>hashCode()</code> returns the same value for
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* equivalent proxies.</li>
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* <li><code>toString()</code> returns a textual representation
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* of the proxy.</li>
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* </ul>
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*
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* @author Andrew John Hughes (gnu_andrew@member.fsf.org)
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* @since 1.5
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*/
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public class MBeanServerInvocationHandler
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implements InvocationHandler
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{
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/**
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* The connection used to make the calls.
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*/
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private MBeanServerConnection conn;
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/**
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* The name of the bean to perform operations on.
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*/
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private ObjectName name;
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/**
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* True if this proxy is for an {@link MXBean}.
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*/
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private boolean mxBean;
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/**
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* The interface class associated with the bean.
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*/
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private Class<?> iface;
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/**
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* Constructs a new {@link MBeanServerInvocationHandler}
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* which forwards methods to the supplied bean via the
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* given {@link MBeanServerConnection}. This constructor
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* is used in preference to
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* {@link JMX#newMBeanProxy(MBeanServerConnection, ObjectName,
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* Class<T>)} if you wish to make your own call to
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* {@link java.lang.reflect.Proxy#newInstance(ClassLoader,
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* Class[], java.lang.reflect.InvocationHandler)} with
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* a different {@link ClassLoader}. Calling this constructor
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* is equivalent to <code>MBeanServerInvocationHandler(conn,
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* name, false)</code>. The other constructor should be used
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* instead if the bean being proxied is an {@link MXBean}.
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*
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* @param conn the connection through which methods will
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* be forwarded to the bean.
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* @param name the name of the bean to use to provide the
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* actual calls.
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*/
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public MBeanServerInvocationHandler(MBeanServerConnection conn,
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ObjectName name)
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{
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this(conn, name, false);
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}
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/**
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* Constructs a new {@link MBeanServerInvocationHandler}
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* which forwards methods to the supplied bean via the
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* given {@link MBeanServerConnection}. This constructor
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* is used in preference to
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* {@link JMX#newMBeanProxy(MBeanServerConnection, ObjectName,
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* Class<T>)} if you wish to make your own call to
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* {@link java.lang.reflect.Proxy#newInstance(ClassLoader,
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* Class[], java.lang.reflect.InvocationHandler)} with
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* a different {@link ClassLoader}.
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*
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* @param conn the connection through which methods will
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* be forwarded to the bean.
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* @param name the name of the bean to use to provide the
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* actual calls.
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* @param mxBean true if the bean being proxied is an
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* {@link MXBean}.
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* @since 1.6
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*/
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public MBeanServerInvocationHandler(MBeanServerConnection conn,
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ObjectName name, boolean mxBean)
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{
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this.conn = conn;
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this.name = name;
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this.mxBean = mxBean;
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}
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/**
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* Returns the connection through which the calls to the bean
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* will be made.
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*
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* @return the connection being used to forward the calls to
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* the bean.
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* @since 1.6
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*/
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public MBeanServerConnection getMBeanServerConnection()
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{
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return conn;
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}
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/**
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* Returns the name of the bean to which method calls are made.
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*
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* @return the bean which provides the actual method calls.
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* @since 1.6
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*/
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public ObjectName getObjectName()
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{
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return name;
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}
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/**
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* Called by the proxy class whenever a method is called. The method
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* is emulated by retrieving an attribute from, setting an attribute on
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* or invoking a method on the server connection as required. Translation
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* between the Java data types supplied as arguments to the open types used
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* by the bean is provided, as well as translation of the return value back
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* in to the appropriate Java type if the bean is an {@link MXBean}.
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*
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* @param proxy the proxy on which the method was called.
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* @param method the method which was called.
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* @param args the arguments supplied to the method.
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* @return the return value from the method.
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* @throws Throwable if an exception is thrown in performing the
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* method emulation.
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*/
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public Object invoke(Object proxy, Method method, Object[] args)
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throws Throwable
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{
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String mName = method.getName();
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Class<?> proxyClass = proxy.getClass();
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if (mName.equals("toString"))
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{
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if (inInterface(mName, proxyClass))
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return conn.invoke(name,mName,null,null);
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else
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return proxyClass.getName() + "[name=" + name
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+ ", conn=" + conn + "]";
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}
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if (mName.equals("hashCode"))
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{
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if (inInterface(mName, proxyClass))
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return conn.invoke(name,mName,null,null);
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else
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return conn.hashCode() + name.hashCode()
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+ (iface == null ? 0 : iface.hashCode());
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}
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if (mName.equals("equals"))
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{
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if (inInterface(mName, proxyClass, Object.class))
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return conn.invoke(name,mName,new Object[]{args[0]},
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new String[]{"java.lang.Object"});
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else
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{
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if (args[0].getClass() != proxy.getClass())
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return false;
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InvocationHandler ih = Proxy.getInvocationHandler(args[0]);
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if (ih instanceof MBeanServerInvocationHandler)
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{
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MBeanServerInvocationHandler h =
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(MBeanServerInvocationHandler) ih;
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return conn.equals(h.getMBeanServerConnection())
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&& name.equals(h.getObjectName())
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&& (iface == null ? h.iface == null
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: iface.equals(h.iface));
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}
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return false;
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}
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}
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if (NotificationEmitter.class.isAssignableFrom(proxyClass))
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{
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if (mName.equals("addNotificationListener"))
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{
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conn.addNotificationListener(name,
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(NotificationListener) args[0],
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(NotificationFilter) args[1],
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args[2]);
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return null;
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}
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if (mName.equals("getNotificationInfo"))
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return conn.getMBeanInfo(name).getNotifications();
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if (mName.equals("removeNotificationListener"))
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{
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if (args.length == 1)
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conn.removeNotificationListener(name,
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(NotificationListener)
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args[0]);
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else
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conn.removeNotificationListener(name,
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(NotificationListener)
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args[0],
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(NotificationFilter)
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args[1], args[2]);
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return null;
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}
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}
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String[] sigs;
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if (args == null)
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sigs = null;
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else
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{
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sigs = new String[args.length];
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for (int a = 0; a < args.length; ++a)
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sigs[a] = args[a].getClass().getName();
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}
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String attrib = null;
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if (mName.startsWith("get"))
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attrib = mName.substring(3);
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else if (mName.startsWith("is"))
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attrib = mName.substring(2);
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if (attrib != null)
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{
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Object val = conn.getAttribute(name, attrib);
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if (mxBean)
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return Translator.toJava(val, method);
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else
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return val;
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}
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else if (mName.startsWith("set"))
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{
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Object arg;
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if (mxBean)
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arg = Translator.fromJava(args, method)[0];
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else
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arg = args[0];
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conn.setAttribute(name, new Attribute(mName.substring(3), arg));
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return null;
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}
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if (mxBean)
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return Translator.toJava(conn.invoke(name, mName,
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Translator.fromJava(args,method),
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sigs), method);
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else
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return conn.invoke(name, mName, args, sigs);
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}
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/**
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* Returns true if this is a proxy for an {@link MXBean}
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* and conversions must be applied to input parameters
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* and return types, according to the rules for such beans.
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*
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* @return true if this is a proxy for an {@link MXBean}.
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* @since 1.6
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*/
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public boolean isMXBean()
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{
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return mxBean;
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}
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/**
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* <p>
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* Returns a proxy for the specified bean. A proxy object is created
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* using <code>Proxy.newProxyInstance(iface.getClassLoader(),
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* new Class[] { iface }, handler)</code>. The
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* {@link javax.management.NotificationEmitter} class is included as the
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* second element of the array if <code>broadcaster</code> is true.
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* <code>handler</code> refers to the invocation handler which forwards
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* calls to the connection, which is created by a call to
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* <code>new MBeanServerInvocationHandler(conn, name)</code>.
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* </p>
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* <p>
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* <strong>Note</strong>: use of the proxy may result in
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* {@link java.io.IOException}s from the underlying
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* {@link MBeanServerConnection}.
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* As of 1.6, the use of {@link JMX#newMBeanProxy(MBeanServerConnection,
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* ObjectName,Class)} and {@link JMX#newMBeanProxy(MBeanServerConnection,
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* ObjectName,Class,boolean)} is preferred.
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* </p>
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*
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* @param conn the server connection to use to access the bean.
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* @param name the {@link javax.management.ObjectName} of the
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* bean to provide a proxy for.
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* @param iface the interface for the bean being proxied.
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* @param broadcaster true if the proxy should implement
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* {@link NotificationEmitter}.
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* @return a proxy for the specified bean.
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* @see JMX#newMBeanProxy(MBeanServerConnection,ObjectName,Class)
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*/
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// Suppress warnings as we know an instance of T will be returned.
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@SuppressWarnings("unchecked")
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public static <T> T newProxyInstance(MBeanServerConnection conn,
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ObjectName name, Class<T> iface,
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boolean broadcaster)
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{
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if (broadcaster)
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return (T) Proxy.newProxyInstance(iface.getClassLoader(),
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new Class[] { iface,
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NotificationEmitter.class },
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new MBeanServerInvocationHandler(conn,name));
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else
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return (T) Proxy.newProxyInstance(iface.getClassLoader(),
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new Class[] { iface },
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new MBeanServerInvocationHandler(conn,name));
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}
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/**
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* Returns true if the specified method is specified
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* by one of the proxy's interfaces.
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*
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* @param name the name of the method to search for.
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* @param proxyClass the class of the proxy.
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* @param args the arguments to the method.
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* @return true if one of the interfaces specifies the
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* given method.
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*/
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private boolean inInterface(String name, Class<?> proxyClass,
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Class<?>... args)
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{
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for (Class<?> iface : proxyClass.getInterfaces())
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{
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try
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{
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iface.getMethod(name, args);
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return true;
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}
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catch (NoSuchMethodException e)
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{
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/* Ignored; this interface doesn't specify
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the method. */
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}
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}
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return false;
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}
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}
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