NamedEventManager.java

/*
** Module   : NamedEventManager.java
** Abstract : provides a publish/subscribe mechanism for interprogram linkage
**
** Copyright (c) 2007-2022, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- -----------------------------------Description-----------------------------------
** 001 GES 20070221   @32210 Created initial version which provides a publish/subscribe mechanism
**                           for interprogram linkage.
** 002 CA  20130130          Added APIs to support all possible parameters for PUBLISH, SUBSCRIBE
**                           and UNSUBSCRIBE.
** 003 CA  20170228          Added PUBLISH/SUBSCRIBE/UNSUBSCRIBE extensions for global support
**                           and for external applications.
** 004 GES 20171206          Update javadoc to match changes to silent error mode. 
** 005 CA  20190219          Changes from adding class event support.
** 006 CA  20190903          Added GLOBAL support for SUBSCRIBE/UNSUBSCRIBE (cross-session messaging).
** 007 CA  20220106          PUBLISH arguments must be evaluated only if the subscription is found.
*/

/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
** 
** Additional terms under GNU Affero GPL version 3 section 7:
** 
**   Under Section 7 of the GNU Affero GPL version 3, the following additional
**   terms apply to the works covered under the License.  These additional terms
**   are non-permissive additional terms allowed under Section 7 of the GNU
**   Affero GPL version 3 and may not be removed by you.
** 
**   0. Attribution Requirement.
** 
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**     work or Appropriate Legal Notices displayed by works containing the covered
**     work.  You may not remove from the covered work any author or developer
**     credit already included within the covered work.
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** 
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**     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
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**     name Golden Code, FWD, or the names of any author or contributor, for
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**     Corporation or FWD.  All modified versions must contain the notices of
**     attribution required in this license.
*/

package com.goldencode.p2j.util;

import java.util.function.*;

/**
 * Provides a publish/subscribe mechanism for interprogram linkage. This
 * corresponds to the following language statements in Progress 4GL. Actual
 * implementation of each statement resides in specific 
 * {@link ProcedureManager} APIs.
 * <p>
 * <pre>
 * PUBLISH                         {@link ProcedureManager#publish}
 * SUBSCRIBE                       {@link ProcedureManager#subscribe}
 *                                 {@link ProcedureManager#subscribeAnywhere}
 * UNSUBSCRIBE                     {@link ProcedureManager#unsubscribe}
 *                                 {@link ProcedureManager#unsubscribeAll}
 * </pre>
 */
public class NamedEventManager
{
   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    */
   public static void publishGlobal(String event, handle publisher)
   {
      publishGlobal(new character(event), publisher, null, null);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    */
   public static void publishGlobal(character event, handle publisher)
   {
      publishGlobal(event, publisher, null, null);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    * @param    modes
    *           The mode for each parameter, encoded in a string. When
    *           <code>null</code>, the parameter modes will not be checked
    *           against the procedure definition.
    * @param    param
    *           The parameters passed to the subscriber. May be
    *           <code>null</code> to represent no parameters.
    */
   public static void publishGlobal(String event, handle publisher, String modes, Supplier<Object[]> param)
   {
      publishGlobal(new character(event), publisher, modes, param);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    * @param    modes
    *           The mode for each parameter, encoded in a string. When
    *           <code>null</code>, the parameter modes will not be checked
    *           against the procedure definition.
    * @param    param
    *           The parameters passed to the subscriber. May be
    *           <code>null</code> to represent no parameters.
    */
   public static void publishGlobal(character event, handle publisher, String modes, Supplier<Object[]> param)
   {
      ProcedureManager.publish(false, true, event, publisher, modes, param);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    */
   public static void publish(String event, handle publisher)
   {
      publish(new character(event), publisher);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    */
   public static void publish(character event, handle publisher)
   {
      publish(event, publisher, null);
   }
   
   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    * @param    param
    *           The parameters passed to the subscriber. May be
    *           <code>null</code> to represent no parameters.
    */
   public static void publish(String event, handle publisher, Supplier<Object[]> param)
   {
      publish(new character(event), publisher, param);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    * @param    param
    *           The parameters passed to the subscriber. May be
    *           <code>null</code> to represent no parameters.
    */
   public static void publish(character event, handle publisher, Supplier<Object[]> param)
   {
      publish(new character(event), publisher, null, param);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    * @param    modes
    *           The mode for each parameter, encoded in a string. When
    *           <code>null</code>, the parameter modes will not be checked
    *           against the procedure definition.
    * @param    param
    *           The parameters passed to the subscriber. May be
    *           <code>null</code> to represent no parameters.
    */
   public static void publish(String event, handle publisher, String modes, Supplier<Object[]> param)
   {
      publish(new character(event), publisher, modes, param);
   }

   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event. Must not be <code>null</code>.
    * @param    modes
    *           The mode for each parameter, encoded in a string. When
    *           <code>null</code>, the parameter modes will not be checked
    *           against the procedure definition.
    * @param    param
    *           The parameters passed to the subscriber. May be
    *           <code>null</code> to represent no parameters.
    */
   public static void publish(character event, handle publisher, String modes, Supplier<Object[]> param)
   {
      ProcedureManager.publish(false, event, publisher, modes, param);
   }
   
   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to a Progress 4GL internal
    *           procedure name created from the given event name.
    * @param    event
    *           The name of the event which is being published.
    */
   public static void subscribe(handle subscriber, String event)
   {
      subscribe(subscriber, new character(event));
   }

   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to a Progress 4GL internal
    *           procedure name created from the given event name.
    * @param    event
    *           The name of the event which is being published.
    */
   public static void subscribe(handle subscriber, character event)
   {
      subscribe(subscriber, event, null);
   }

   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to a Progress 4GL internal
    *           procedure name created from the given event name.
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the named event will only
    *           cause a notification if the event source matches this handle.
    *           <code>null</code> represents the <code>ANYWHERE</code> option
    *           which means that the events will not be filtered by source.
    */
   public static void subscribe(handle subscriber,
                                String event,
                                handle publisher)
   {
      subscribe(subscriber, new character(event), publisher);
   }

   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to a Progress 4GL internal
    *           procedure name created from the given event name.
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the named event will only
    *           cause a notification if the event source matches this handle.
    *           <code>null</code> represents the <code>ANYWHERE</code> option
    *           which means that the events will not be filtered by source.
    */
   public static void subscribe(handle    subscriber,
                                character event,
                                handle    publisher)
   {
      subscribe(subscriber, event, publisher, (character) null);
   }

   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the named event will only
    *           cause a notification if the event source matches this handle.
    *           <code>null</code> represents the <code>ANYWHERE</code> option
    *           which means that the events will not be filtered by source.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribe(handle subscriber,
                                String event,
                                handle publisher,
                                String method)
   {
      subscribe(subscriber,
                new character(event), 
                publisher,
                new character(method));
   }

   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the named event will only
    *           cause a notification if the event source matches this handle.
    *           <code>null</code> represents the <code>ANYWHERE</code> option
    *           which means that the events will not be filtered by source.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribe(handle    subscriber,
                                String    event,
                                handle    publisher,
                                character method)
   {
      subscribe(subscriber, new character(event), publisher, method);
   }

   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the named event will only
    *           cause a notification if the event source matches this handle.
    *           <code>null</code> represents the <code>ANYWHERE</code> option
    *           which means that the events will not be filtered by source.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribe(handle    subscriber,
                                character event,
                                handle    publisher,
                                String    method)
   {
      subscribe(subscriber, event, publisher, new character(method));
   }
   
   /**
    * Create a new subscription to the given event for a specified program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the named event will only
    *           cause a notification if the event source matches this handle.
    *           <code>null</code> represents the <code>ANYWHERE</code> option
    *           which means that the events will not be filtered by source.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribe(handle    subscriber,
                                character event,
                                handle    publisher,
                                character method)
   {
      ProcedureManager.subscribe(false, subscriber, event, publisher, method, null);
   }
   
   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    */
   public static void subscribeAnywhere(handle subscriber, String event)
   {
      subscribeAnywhere(subscriber, new character(event));
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    */
   public static void subscribeAnywhere(handle subscriber, character event)
   {
      subscribeAnywhere(subscriber, event, (character) null);
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeAnywhere(handle subscriber,
                                        String event,
                                        String method)
   {
      subscribeAnywhere(subscriber,
                        new character(event),
                        new character(method));
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeAnywhere(handle    subscriber,
                                        character event,
                                        String    method)
   {
      subscribeAnywhere(subscriber, event, new character(method));
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeAnywhere(handle    subscriber,
                                        String    event,
                                        character method)
   {
      subscribeAnywhere(subscriber, new character(event), method);
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeAnywhere(handle    subscriber,
                                        character event,
                                        character method)
   {
      ProcedureManager.subscribeAnywhere(false, subscriber, event, method);
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    */
   public static void subscribeGlobal(handle subscriber, String event)
   {
      subscribeGlobal(subscriber, new character(event));
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    */
   public static void subscribeGlobal(handle subscriber, character event)
   {
      subscribeGlobal(subscriber, event, (character) null);
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeGlobal(handle subscriber, String event, String method)
   {
      subscribeGlobal(subscriber, new character(event), new character(method));
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeGlobal(handle subscriber, character event, String method)
   {
      subscribeGlobal(subscriber, event, new character(method));
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeGlobal(handle subscriber, String event, character method)
   {
      subscribeGlobal(subscriber, new character(event), method);
   }

   /**
    * Create a new subscription to the given event for any program.
    * This program will receive a call-back when the event is published.
    *
    * @param    subscriber
    *           The program to notify when the specified event is published.
    *           Must not be <code>null</code>.  The specified program must
    *           have a method that corresponds to the given Progress 4GL
    *           internal procedure name (<code>method</code>).
    * @param    event
    *           The name of the event which is being published.
    * @param    method
    *           The Progress 4GL internal procedure name which will be
    *           translated into a method name and invoked on the 
    *           <code>subscriber</code> instance. 
    */
   public static void subscribeGlobal(handle subscriber, character event, character method)
   {
      ProcedureManager.subscribeAnywhere(true, subscriber, event, method);
   }

   /**
    * Create a new subscription to the given event for a specified external resource. 
    * This resource will receive a notification when the event is published.
    *
    * @param    global
    *           Flag indicating if the subscription is for global (cross-session) events.
    * @param    subscriber
    *           The resource to notify when the specified event is published. If <code>null</code>,
    *           a {@link ExternalResource} will be built and its ID return.
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The handle representing the program or resource that is the source of the event. 
    *           If specified, the named event will only cause a notification if the event source 
    *           matches this handle. <code>null</code> represents the <code>ANYWHERE</code> option
    *           which means that the events will not be filtered by source.
    * 
    * @return   The subscriber's ID.
    */
   public static handle subscribeExternal(boolean global, 
                                          handle  subscriber, 
                                          String  event, 
                                          handle  publisher)
   {
      return ProcedureManager.subscribeExternal(global, subscriber, event, publisher);
   }

   /**
    * Delete a subscription to the given event for the specified external resource.  This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    global
    *           Flag indicating if the search is done in the global (cross-session) event register.
    * @param    subscriber
    *           The resource whose subscription is to be deleted.  Must not be <code>null</code>.
    * @param    event
    *           The name of the event which is being published. If this is <code>null</code>, then
    *           subscriptions to all events will be deleted.
    * @param    publisher
    *           The procedure or resource handle representing the source of the event.
    *           If specified, the subscription will only be deleted if the event source matches
    *           this handle.  <code>null</code> represents the <code>ALL</code> option which means
    *           that the events will not be filtered by source. When <code>null</code>, it means
    *           that the publisher was not set.
    */
   public static void unsubscribeExternal(boolean global, 
                                          handle  subscriber, 
                                          String  event,
                                          handle  publisher)
   {
      ProcedureManager.unsubscribeExternal(global, subscriber, event, publisher);
   }
   
   /**
    * Notify all subscribers (to the given event) that the event has occurred. This method is
    * executed in a {@link ErrorManager#silent} bracket, as the <code>PUBLISH</code>
    * statement is executed with a default NO-ERROR clause.
    * <p>
    * All processing is done with silent error mode implicitly enabled.
    * <p>
    * The subscriptions are fired in the order they were subscribed. Although 4GL
    * documentation specifically states, that "If a named event has multiple subscribers, 
    * the order in which the AVM notifies subscribers is undefined.", the actual
    * 4GL implementation (OpenEdge 10.2B) does fire the events in the order the subscriptions
    * get subscribed.
    *
    * @param    event
    *           The name of the event which is being published.
    * @param    publisher
    *           The procedure or resource handle representing the program that is the source of  
    *           the event. Must not be <code>null</code>.
    * @param    args
    *           The parameters passed to the subscriber. May be <code>null</code> to represent no
    *           parameters. When <code>null</code>, it means that no parameters were specified for
    *           this call.
    */
   public static void publishExternal(String event, handle publisher, String[] args)
   {
      ProcedureManager.publishExternal(event, publisher, args);
   }
   
   /**
    * Delete a subscription to the given event for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    * @param    event
    *           The name of the event which is being published. If this is
    *           <code>null</code>, then subscriptions to all events will be
    *           deleted.
    */
   public static void unsubscribe(handle subscriber, String event)
   {
      unsubscribe(subscriber, new character(event));
   }
   
   /**
    * Delete a subscription to the given event for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    * @param    event
    *           The name of the event which is being published. If this is
    *           <code>null</code>, then subscriptions to all events will be
    *           deleted.
    */
   public static void unsubscribe(handle subscriber, character event)
   {
      unsubscribe(subscriber, event, null);
   }
   
   /**
    * Delete a subscription to the given event for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    * @param    event
    *           The name of the event which is being published. If this is
    *           <code>null</code>, then subscriptions to all events will be
    *           deleted.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the subscription will only
    *           be deleted if the event source matches this handle.
    *           <code>null</code> represents the <code>ALL</code> option
    *           which means that the events will not be filtered by source.
    */
   public static void unsubscribe(handle subscriber, String event, handle publisher)
   {
      unsubscribe(subscriber, new character(event), publisher);
   }
   
   /**
    * Delete a subscription to the given event for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    * @param    event
    *           The name of the event which is being published. If this is
    *           <code>null</code>, then subscriptions to all events will be
    *           deleted.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the subscription will only
    *           be deleted if the event source matches this handle.
    *           <code>null</code> represents the <code>ALL</code> option
    *           which means that the events will not be filtered by source.
    */
   public static void unsubscribe(handle subscriber, character event, handle publisher)
   {
      ProcedureManager.unsubscribe(false, subscriber, event, publisher, null);
   }

   /**
    * Delete a subscription to ALL events for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    */
   public static void unsubscribeAll(handle subscriber)
   {
      unsubscribeAll(subscriber, null);
   }

   /**
    * Delete a subscription to ALL events for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    * @param    publisher
    *           The procedure handle representing the program that is the
    *           source of the event.  If specified, the subscription will only
    *           be deleted if the event source matches this handle.
    *           <code>null</code> represents the <code>ALL</code> option
    *           which means that the events will not be filtered by source.
    */
   public static void unsubscribeAll(handle subscriber, handle publisher)
   {
      ProcedureManager.unsubscribeAll(false, subscriber, publisher);
   }

   
   /**
    * Delete a subscription to the given event for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    * @param    event
    *           The name of the event which is being published. If this is
    *           <code>null</code>, then subscriptions to all events will be
    *           deleted.
    */
   public static void unsubscribeGlobal(handle subscriber, String event)
   {
      unsubscribeGlobal(subscriber, new character(event));
   }
   
   /**
    * Delete a subscription to the given event for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    * @param    event
    *           The name of the event which is being published. If this is
    *           <code>null</code>, then subscriptions to all events will be
    *           deleted.
    */
   public static void unsubscribeGlobal(handle subscriber, character event)
   {
      ProcedureManager.unsubscribe(true, subscriber, event, null, null);
   }

   /**
    * Delete a subscription to ALL events for the specified program. This method is 
    * executed in a {@link ErrorManager#silent} bracket, as the <code>UNSUBSCRIBE</code>
    * statement is executed with a default NO-ERROR clause.
    *
    * @param    subscriber
    *           The program whose subscription is to be deleted.  Must not
    *           be <code>null</code>.
    */
   public static void unsubscribeAllGlobal(handle subscriber)
   {
      ProcedureManager.unsubscribeAll(true, subscriber, null);
   }
}