otpmbox.java

来自「OTP是开放电信平台的简称」· Java 代码 · 共 652 行 · 第 1/2 页

/* ``The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved via the world wide web at http://www.erlang.org/.
 * 
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 * 
 * The Initial Developer of the Original Code is Ericsson Utvecklings AB.
 * Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
 * AB. All Rights Reserved.''
 * 
 *     $Id$
 */
package com.ericsson.otp.erlang;

/**
 * <p> Provides a simple mechanism for exchanging messages with Erlang
 * processes or other instances of this class.</p>
 *
 * <p> Each mailbox is associated with a unique {@link OtpErlangPid
 * pid} that contains information necessary for delivery of messages.
 * When sending messages to named processes or mailboxes, the sender
 * pid is made available to the recipient of the message. When sending
 * messages to other mailboxes, the recipient can only respond if the
 * sender includes the pid as part of the message contents. The sender
 * can determine his own pid by calling {@link #self self()}. </p>
 *
 * <p> Mailboxes can be named, either at creation or later. Messages
 * can be sent to named mailboxes and named Erlang processes without
 * knowing the {@link OtpErlangPid pid} that identifies the mailbox.
 * This is neccessary in order to set up initial communication between
 * parts of an application. Each mailbox can have at most one name.
 * </p>
 *
 * <p> Since this class was intended for communication with Erlang,
 * all of the send methods take {@link OtpErlangObject
 * OtpErlangObject} arguments. However this class can also be used to
 * transmit arbitrary Java objects (as long as they implement one of
 * java.io.Serializable or java.io.Externalizable) by encapsulating
 * the object in a {@link OtpErlangBinary OtpErlangBinary}. </p>
 *
 * <p> Messages to remote nodes are externalized for transmission, and
 * as a result the recipient receives a <b>copy</b> of the original
 * Java object. To ensure consistent behaviour when messages are sent
 * between local mailboxes, such messages are cloned before delivery.
 * </p>
 *
 * <p> Additionally, mailboxes can be linked in much the same way as
 * Erlang processes. If a link is active when a mailbox is {@link
 * #close closed}, any linked Erlang processes or OtpMboxes will be
 * sent an exit signal. As well, exit signals will be (eventually)
 * sent if a mailbox goes out of scope and its {@link #finalize
 * finalize()} method called. However due to the nature of
 * finalization (i.e. Java makes no guarantees about when {@link
 * #finalize finalize()} will be called) it is recommended that you
 * always explicitly close mailboxes if you are using links instead of
 * relying on finalization to notify other parties in a timely manner.
 * </p>
 *
 * When retrieving messages from a mailbox that has received an exit
 * signal, an {@link OtpErlangExit OtpErlangExit} exception will be
 * raised. Note that the exception is queued in the mailbox along with
 * other messages, and will not be raised until it reaches the head of
 * the queue and is about to be retrieved. </p>
 *
 **/
public class OtpMbox {
  OtpNode home;
  OtpErlangPid self;
  GenericQueue queue;
  String name;
  Links links;

  // package constructor: called by OtpNode:createMbox(name)
  // to create a named mbox
  OtpMbox(OtpNode home, OtpErlangPid self, String name) {
    this.self = self;
    this.home = home;
    this.name = name;
    this.queue = new GenericQueue();
    this.links = new Links(10);
  }

  // package constructor: called by OtpNode:createMbox() 
  // to create an anonymous
  OtpMbox(OtpNode home, OtpErlangPid self) {
    this(home,self,null);
  }

  
  /**
   * <p> Get the identifying {@link OtpErlangPid pid} associated with
   * this mailbox.</p>
   *
   * <p> The {@link OtpErlangPid pid} associated with this mailbox
   * uniquely identifies the mailbox and can be used to address the
   * mailbox. You can send the {@link OtpErlangPid pid} to a remote
   * communicating part so that he can know where to send his
   * response. </p>
   *   
   * @return the self pid for this mailbox.
   **/
  public OtpErlangPid self() {
    return self;
  }


  /**
   * <p> Register or remove a name for this mailbox. Registering a
   * name for a mailbox enables others to send messages without
   * knowing the {@link OtpErlangPid pid} of the mailbox. A mailbox
   * can have at most one name; if the mailbox already had a name,
   * calling this method will supercede that name. </p>
   *
   * @param name the name to register for the mailbox. Specify null to
   * unregister the existing name from this mailbox.
   *
   * @return true if the name was available, or false otherwise.
   **/
  public synchronized boolean registerName(String name) {
    return home.registerName(name,this);
  }


  /**
   * Get the registered name of this mailbox.
   *
   * @return the registered name of this mailbox, or null if the
   * mailbox had no registerd name.
   **/
  public String getName() {
    return this.name;
  }


  /** 
   * Block until a message arrives for this mailbox.
   *
   * @return an {@link OtpErlangObject OtpErlangObject} representing
   * the body of the next message waiting in this mailbox.
   *
   * @exception OtpErlangDecodeException if the message can not be
   * decoded.
   *
   * @exception OtpErlangExit if a linked {@link OtpErlangPid pid} has
   * exited or has sent an exit signal to this mailbox.
   **/
  public OtpErlangObject receive() 
    throws OtpErlangExit, OtpErlangDecodeException {
    try {
      return receiveMsg().getMsg();
    }
    catch (OtpErlangExit e) {
      throw e;
    }
    catch (OtpErlangDecodeException f) {
      throw f;
    }
  }
  
  /**
   * Wait for a message to arrive for this mailbox.
   *
   * @param timeout the time, in milliseconds, to wait for a message
   * before returning null.
   *
   * @return an {@link OtpErlangObject OtpErlangObject} representing
   * the body of the next message waiting in this mailbox.
   *
   * @exception OtpErlangDecodeException if the message can not be
   * decoded.
   *
   * @exception OtpErlangExit if a linked {@link OtpErlangPid pid} has
   * exited or has sent an exit signal to this mailbox.
   **/
  public OtpErlangObject receive(long timeout) 
    throws OtpErlangExit, OtpErlangDecodeException {
    try {
      OtpMsg m = receiveMsg(timeout);
      if (m != null) return m.getMsg();
    }
    catch (OtpErlangExit e) {
      throw e;
    }
    catch (OtpErlangDecodeException f) {
      throw f;
    }
    catch (InterruptedException g) { }
    return null;
  }

  /**
   * Block until a message arrives for this mailbox.
   *
   * @return a byte array representing the still-encoded body of the
   * next message waiting in this mailbox.
   *
   * @exception OtpErlangExit if a linked {@link OtpErlangPid pid} has
   * exited or has sent an exit signal to this mailbox.
   *
   **/
  public OtpInputStream receiveBuf() 
    throws OtpErlangExit {
    return receiveMsg().getMsgBuf();
  }

  /**
   * Wait for a message to arrive for this mailbox.
   *
   * @param timeout the time, in milliseconds, to wait for a message
   * before returning null.
   *
   * @return a byte array representing the still-encoded body of the
   * next message waiting in this mailbox.
   *
   * @exception OtpErlangExit if a linked {@link OtpErlangPid pid} has
   * exited or has sent an exit signal to this mailbox.
   *
   * @exception InterruptedException if no message if the method
   * times out before a message becomes available.
   **/
  public OtpInputStream receiveBuf(long timeout) 
    throws InterruptedException, OtpErlangExit {
    OtpMsg m = receiveMsg(timeout);
    if (m != null) return m.getMsgBuf();

    return null;
  }

  /**
   * Block until a message arrives for this mailbox.
   *
   * @return an {@link OtpMsg OtpMsg} containing the header
   * information as well as the body of the next message waiting in
   * this mailbox.
   *
   * @exception OtpErlangExit if a linked {@link OtpErlangPid pid} has
   * exited or has sent an exit signal to this mailbox.
   *
   **/
  public OtpMsg receiveMsg() 
    throws OtpErlangExit {

    OtpMsg m = (OtpMsg)(queue.get());

    switch (m.type()) {
    case OtpMsg.exitTag:
    case OtpMsg.exit2Tag:
      try {
	OtpErlangObject o = m.getMsg();
	throw new OtpErlangExit(o,m.getSenderPid());
      }
      catch (OtpErlangDecodeException e) {
	throw new OtpErlangExit("unknown",m.getSenderPid());
      }
      
    default:
      return m;
    }
  }

  /**
   * Wait for a message to arrive for this mailbox.
   *
   * @param timeout the time, in milliseconds, to wait for a message.
   *
   * @return an {@link OtpMsg OtpMsg} containing the header
   * information as well as the body of the next message waiting in
   * this mailbox.
   *
   * @exception OtpErlangExit if a linked {@link OtpErlangPid pid} has
   * exited or has sent an exit signal to this mailbox.
   *
   * @exception InterruptedException if no message if the method
   * times out before a message becomes available.
   **/
  public OtpMsg receiveMsg(long timeout)
    throws InterruptedException, OtpErlangExit {
    OtpMsg m = (OtpMsg)(queue.get(timeout));

    if (m == null) return null;
      
    switch (m.type()) {
    case OtpMsg.exitTag:
    case OtpMsg.exit2Tag:
      try {
	OtpErlangObject o = m.getMsg();
	throw new OtpErlangExit(o,m.getSenderPid());
      }
      catch (OtpErlangDecodeException e) {
	throw new OtpErlangExit("unknown",m.getSenderPid());
      }
      
    default:
      return m;
    }
  }

  /**
   * Send a message to a remote {@link OtpErlangPid pid}, representing
   * either another {@link OtpMbox mailbox} or an Erlang process.
   *
   * @param to the {@link OtpErlangPid pid} identifying the intended
   * recipient of the message.
   *
   * @param msg the body of the message to send.
   *
   **/
  public void send(OtpErlangPid to, OtpErlangObject msg) {
    try {
      String node = to.node();
      if (node.equals(home.node())) {
	home.deliver(new OtpMsg(to,(OtpErlangObject)(msg.clone())));
      }
      else {
	OtpCookedConnection conn = home.getConnection(node);
	if (conn == null) return;
	conn.send(self,to,msg);
      }
    }
    catch (Exception e) { }
  }