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package javax.management.remote;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.management.MBeanNotificationInfo;
import javax.management.MBeanRegistration;
import javax.management.MBeanServer;
import javax.management.Notification;
import javax.management.NotificationBroadcasterSupport;
import javax.management.ObjectName;


Superclass of every connector server.  A connector server is
attached to an MBean server.  It listens for client connection
requests and creates a connection for each one.


A connector server is associated with an MBean server either by
registering it in that MBean server, or by passing the MBean server
to its constructor.


A connector server is inactive when created. It only starts listening for client connections when the start method is called. A connector server stops listening for client connections when the stop method is called or when the connector server is unregistered from its MBean server.


Stopping a connector server does not unregister it from its
MBean server.  A connector server once stopped cannot be
restarted.


Each time a client connection is made or broken, a notification of class JMXConnectionNotification is emitted.


Since:1.5
/**
 * <p>Superclass of every connector server.  A connector server is
 * attached to an MBean server.  It listens for client connection
 * requests and creates a connection for each one.</p>
 *
 * <p>A connector server is associated with an MBean server either by
 * registering it in that MBean server, or by passing the MBean server
 * to its constructor.</p>
 *
 * <p>A connector server is inactive when created.  It only starts
 * listening for client connections when the {@link #start() start}
 * method is called.  A connector server stops listening for client
 * connections when the {@link #stop() stop} method is called or when
 * the connector server is unregistered from its MBean server.</p>
 *
 * <p>Stopping a connector server does not unregister it from its
 * MBean server.  A connector server once stopped cannot be
 * restarted.</p>
 *
 * <p>Each time a client connection is made or broken, a notification
 * of class {@link JMXConnectionNotification} is emitted.</p>
 *
 * @since 1.5
 */
public abstract class JMXConnectorServer
        extends NotificationBroadcasterSupport
        implements JMXConnectorServerMBean, MBeanRegistration, JMXAddressable {

    
Name of the attribute that specifies the authenticator for a connector server. The value associated with this attribute, if any, must be an object that implements the interface JMXAuthenticator.


/**
     * <p>Name of the attribute that specifies the authenticator for a
     * connector server.  The value associated with this attribute, if
     * any, must be an object that implements the interface {@link
     * JMXAuthenticator}.</p>
     */
    public static final String AUTHENTICATOR =
        "jmx.remote.authenticator";

    
Constructs a connector server that will be registered as an
MBean in the MBean server it is attached to.  This constructor
is typically called by one of the createMBean
methods when creating, within an MBean server, a connector
server that makes it available remotely.


/**
     * <p>Constructs a connector server that will be registered as an
     * MBean in the MBean server it is attached to.  This constructor
     * is typically called by one of the <code>createMBean</code>
     * methods when creating, within an MBean server, a connector
     * server that makes it available remotely.</p>
     */
    public JMXConnectorServer() {
        this(null);
    }

    
Constructs a connector server that is attached to the given
MBean server.  A connector server that is created in this way
can be registered in a different MBean server, or not registered
in any MBean server.


Params:
  • mbeanServer – the MBean server that this connector server
is attached to.  Null if this connector server will be attached
to an MBean server by being registered in it.
/**
     * <p>Constructs a connector server that is attached to the given
     * MBean server.  A connector server that is created in this way
     * can be registered in a different MBean server, or not registered
     * in any MBean server.</p>
     *
     * @param mbeanServer the MBean server that this connector server
     * is attached to.  Null if this connector server will be attached
     * to an MBean server by being registered in it.
     */
    public JMXConnectorServer(MBeanServer mbeanServer) {
        this.mbeanServer = mbeanServer;
    }

    
Returns the MBean server that this connector server is
attached to.


Returns:the MBean server that this connector server is attached
to, or null if it is not yet attached to an MBean server.
/**
     * <p>Returns the MBean server that this connector server is
     * attached to.</p>
     *
     * @return the MBean server that this connector server is attached
     * to, or null if it is not yet attached to an MBean server.
     */
    public synchronized MBeanServer getMBeanServer() {
        return mbeanServer;
    }

    public synchronized void setMBeanServerForwarder(MBeanServerForwarder mbsf)
    {
        if (mbsf == null)
            throw new IllegalArgumentException("Invalid null argument: mbsf");

        if (mbeanServer !=  null) mbsf.setMBeanServer(mbeanServer);
        mbeanServer = mbsf;
    }

    public String[] getConnectionIds() {
        synchronized (connectionIds) {
            return connectionIds.toArray(new String[connectionIds.size()]);
        }
    }

    
Returns a client stub for this connector server. A client stub is a serializable object whose connect method can be used to make one new connection to this connector server.


A given connector need not support the generation of client
stubs.  However, the connectors specified by the JMX Remote API do
(JMXMP Connector and RMI Connector).


The default implementation of this method uses JMXConnectorServerMBean.getAddress and JMXConnectorFactory to generate the stub, with code equivalent to the following:


JMXServiceURL addr = getAddress(); return 
         JMXConnectorFactory.newJMXConnector(addr, env); 


A connector server for which this is inappropriate must override this method so that it either implements the appropriate logic or throws UnsupportedOperationException.


Params:
  • env – client connection parameters of the same sort that could be provided to 
JMXConnector.connect(Map). Can be null, which is equivalent to an empty map.
Throws:
Returns:a client stub that can be used to make a new connection
to this connector server.
/**
     * <p>Returns a client stub for this connector server.  A client
     * stub is a serializable object whose {@link
     * JMXConnector#connect(Map) connect} method can be used to make
     * one new connection to this connector server.</p>
     *
     * <p>A given connector need not support the generation of client
     * stubs.  However, the connectors specified by the JMX Remote API do
     * (JMXMP Connector and RMI Connector).</p>
     *
     * <p>The default implementation of this method uses {@link
     * #getAddress} and {@link JMXConnectorFactory} to generate the
     * stub, with code equivalent to the following:</p>
     *
     * <pre>
     * JMXServiceURL addr = {@link #getAddress() getAddress()};
     * return {@link JMXConnectorFactory#newJMXConnector(JMXServiceURL, Map)
     *          JMXConnectorFactory.newJMXConnector(addr, env)};
     * </pre>
     *
     * <p>A connector server for which this is inappropriate must
     * override this method so that it either implements the
     * appropriate logic or throws {@link
     * UnsupportedOperationException}.</p>
     *
     * @param env client connection parameters of the same sort that
     * could be provided to {@link JMXConnector#connect(Map)
     * JMXConnector.connect(Map)}.  Can be null, which is equivalent
     * to an empty map.
     *
     * @return a client stub that can be used to make a new connection
     * to this connector server.
     *
     * @exception UnsupportedOperationException if this connector
     * server does not support the generation of client stubs.
     *
     * @exception IllegalStateException if the JMXConnectorServer is
     * not started (see {@link JMXConnectorServerMBean#isActive()}).
     *
     * @exception IOException if a communications problem means that a
     * stub cannot be created.
     **/
    public JMXConnector toJMXConnector(Map<String,?> env)
        throws IOException
    {
        if (!isActive()) throw new
            IllegalStateException("Connector is not active");
        JMXServiceURL addr = getAddress();
        return JMXConnectorFactory.newJMXConnector(addr, env);
    }

    
Returns an array indicating the notifications that this MBean
sends. The implementation in JMXConnectorServer returns an array with one element, indicating that it can emit notifications of class JMXConnectionNotification with the types defined in that class. A subclass that can emit other notifications should return an array that contains this element plus descriptions of the other notifications.


Returns:the array of possible notifications.
/**
     * <p>Returns an array indicating the notifications that this MBean
     * sends. The implementation in <code>JMXConnectorServer</code>
     * returns an array with one element, indicating that it can emit
     * notifications of class {@link JMXConnectionNotification} with
     * the types defined in that class.  A subclass that can emit other
     * notifications should return an array that contains this element
     * plus descriptions of the other notifications.</p>
     *
     * @return the array of possible notifications.
     */
    @Override
    public MBeanNotificationInfo[] getNotificationInfo() {
        final String[] types = {
            JMXConnectionNotification.OPENED,
            JMXConnectionNotification.CLOSED,
            JMXConnectionNotification.FAILED,
        };
        final String className = JMXConnectionNotification.class.getName();
        final String description =
            "A client connection has been opened or closed";
        return new MBeanNotificationInfo[] {
            new MBeanNotificationInfo(types, className, description),
        };
    }

    
Called by a subclass when a new client connection is opened.
Adds connectionId to the list returned by getConnectionIds(), then emits a JMXConnectionNotification with type JMXConnectionNotification.OPENED.


Params:
Throws:
  • NullPointerException – if connectionId is
null.
/**
     * <p>Called by a subclass when a new client connection is opened.
     * Adds <code>connectionId</code> to the list returned by {@link
     * #getConnectionIds()}, then emits a {@link
     * JMXConnectionNotification} with type {@link
     * JMXConnectionNotification#OPENED}.</p>
     *
     * @param connectionId the ID of the new connection.  This must be
     * different from the ID of any connection previously opened by
     * this connector server.
     *
     * @param message the message for the emitted {@link
     * JMXConnectionNotification}.  Can be null.  See {@link
     * Notification#getMessage()}.
     *
     * @param userData the <code>userData</code> for the emitted
     * {@link JMXConnectionNotification}.  Can be null.  See {@link
     * Notification#getUserData()}.
     *
     * @exception NullPointerException if <code>connectionId</code> is
     * null.
     */
    protected void connectionOpened(String connectionId,
                                    String message,
                                    Object userData) {

        if (connectionId == null)
            throw new NullPointerException("Illegal null argument");

        synchronized (connectionIds) {
            connectionIds.add(connectionId);
        }

        sendNotification(JMXConnectionNotification.OPENED, connectionId,
                         message, userData);
    }

    
Called by a subclass when a client connection is closed
normally.  Removes connectionId from the list returned by getConnectionIds(), then emits a JMXConnectionNotification with type JMXConnectionNotification.CLOSED.


Params:
Throws:
/**
     * <p>Called by a subclass when a client connection is closed
     * normally.  Removes <code>connectionId</code> from the list returned
     * by {@link #getConnectionIds()}, then emits a {@link
     * JMXConnectionNotification} with type {@link
     * JMXConnectionNotification#CLOSED}.</p>
     *
     * @param connectionId the ID of the closed connection.
     *
     * @param message the message for the emitted {@link
     * JMXConnectionNotification}.  Can be null.  See {@link
     * Notification#getMessage()}.
     *
     * @param userData the <code>userData</code> for the emitted
     * {@link JMXConnectionNotification}.  Can be null.  See {@link
     * Notification#getUserData()}.
     *
     * @exception NullPointerException if <code>connectionId</code>
     * is null.
     */
    protected void connectionClosed(String connectionId,
                                    String message,
                                    Object userData) {

        if (connectionId == null)
            throw new NullPointerException("Illegal null argument");

        synchronized (connectionIds) {
            connectionIds.remove(connectionId);
        }

        sendNotification(JMXConnectionNotification.CLOSED, connectionId,
                         message, userData);
    }

    
Called by a subclass when a client connection fails.
Removes connectionId from the list returned by getConnectionIds(), then emits a JMXConnectionNotification with type JMXConnectionNotification.FAILED.


Params:
Throws:
/**
     * <p>Called by a subclass when a client connection fails.
     * Removes <code>connectionId</code> from the list returned by
     * {@link #getConnectionIds()}, then emits a {@link
     * JMXConnectionNotification} with type {@link
     * JMXConnectionNotification#FAILED}.</p>
     *
     * @param connectionId the ID of the failed connection.
     *
     * @param message the message for the emitted {@link
     * JMXConnectionNotification}.  Can be null.  See {@link
     * Notification#getMessage()}.
     *
     * @param userData the <code>userData</code> for the emitted
     * {@link JMXConnectionNotification}.  Can be null.  See {@link
     * Notification#getUserData()}.
     *
     * @exception NullPointerException if <code>connectionId</code> is
     * null.
     */
    protected void connectionFailed(String connectionId,
                                    String message,
                                    Object userData) {

        if (connectionId == null)
            throw new NullPointerException("Illegal null argument");

        synchronized (connectionIds) {
            connectionIds.remove(connectionId);
        }

        sendNotification(JMXConnectionNotification.FAILED, connectionId,
                         message, userData);
    }

    private void sendNotification(String type, String connectionId,
                                  String message, Object userData) {
        Notification notif =
            new JMXConnectionNotification(type,
                                          getNotificationSource(),
                                          connectionId,
                                          nextSequenceNumber(),
                                          message,
                                          userData);
        sendNotification(notif);
    }

    private synchronized Object getNotificationSource() {
        if (myName != null)
            return myName;
        else
            return this;
    }

    private static long nextSequenceNumber() {
        synchronized (sequenceNumberLock) {
            return sequenceNumber++;
        }
    }

    // implements MBeanRegistration
    
Called by an MBean server when this connector server is registered in that MBean server. This connector server becomes attached to the MBean server and its getMBeanServer() method will return mbs.


If this connector server is already attached to an MBean
server, this method has no effect.  The MBean server it is
attached to is not necessarily the one it is being registered
in.


Params:
  • mbs – the MBean server in which this connection server is
being registered.
  • name – The object name of the MBean.
Throws:
Returns:The name under which the MBean is to be registered.
/**
     * <p>Called by an MBean server when this connector server is
     * registered in that MBean server.  This connector server becomes
     * attached to the MBean server and its {@link #getMBeanServer()}
     * method will return <code>mbs</code>.</p>
     *
     * <p>If this connector server is already attached to an MBean
     * server, this method has no effect.  The MBean server it is
     * attached to is not necessarily the one it is being registered
     * in.</p>
     *
     * @param mbs the MBean server in which this connection server is
     * being registered.
     *
     * @param name The object name of the MBean.
     *
     * @return The name under which the MBean is to be registered.
     *
     * @exception NullPointerException if <code>mbs</code> or
     * <code>name</code> is null.
     */
    public synchronized ObjectName preRegister(MBeanServer mbs,
                                               ObjectName name) {
        if (mbs == null || name == null)
            throw new NullPointerException("Null MBeanServer or ObjectName");
        if (mbeanServer == null) {
            mbeanServer = mbs;
            myName = name;
        }
        return name;
    }

    public void postRegister(Boolean registrationDone) {
        // do nothing
    }

    
Called by an MBean server when this connector server is unregistered from that MBean server. If this connector server was attached to that MBean server by being registered in it, and if the connector server is still active, then unregistering it will call the stop method. If the stop method throws an exception, the
unregistration attempt will fail.  It is recommended to call
the stop method explicitly before unregistering
the MBean.


Throws:
/**
     * <p>Called by an MBean server when this connector server is
     * unregistered from that MBean server.  If this connector server
     * was attached to that MBean server by being registered in it,
     * and if the connector server is still active,
     * then unregistering it will call the {@link #stop stop} method.
     * If the <code>stop</code> method throws an exception, the
     * unregistration attempt will fail.  It is recommended to call
     * the <code>stop</code> method explicitly before unregistering
     * the MBean.</p>
     *
     * @exception IOException if thrown by the {@link #stop stop} method.
     */
    public synchronized void preDeregister() throws Exception {
        if (myName != null && isActive()) {
            stop();
            myName = null; // just in case stop is buggy and doesn't stop
        }
    }

    public void postDeregister() {
        myName = null;
    }

    
The MBeanServer used by this server to execute a client request.

/**
     * The MBeanServer used by this server to execute a client request.
     */
    private MBeanServer mbeanServer = null;

    
The name used to registered this server in an MBeanServer.
It is null if the this server is not registered or has been unregistered.

/**
     * The name used to registered this server in an MBeanServer.
     * It is null if the this server is not registered or has been unregistered.
     */
    private ObjectName myName;

    private final List<String> connectionIds = new ArrayList<String>();

    private static final int[] sequenceNumberLock = new int[0];
    private static long sequenceNumber;
}