/*
* Copyright (c) 2001-2007 Sun Microsystems, Inc. All rights reserved.
*
* The Sun Project JXTA(TM) Software License
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The end-user documentation included with the redistribution, if any, must
* include the following acknowledgment: "This product includes software
* developed by Sun Microsystems, Inc. for JXTA(TM) technology."
* Alternately, this acknowledgment may appear in the software itself, if
* and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
* not be used to endorse or promote products derived from this software
* without prior written permission. For written permission, please contact
* Project JXTA at http://www.jxta.org.
*
* 5. Products derived from this software may not be called "JXTA", nor may
* "JXTA" appear in their name, without prior written permission of Sun.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SUN
* MICROSYSTEMS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* JXTA is a registered trademark of Sun Microsystems, Inc. in the United
* States and other countries.
*
* Please see the license information page at :
* <http://www.jxta.org/project/www/license.html> for instructions on use of
* the license in source files.
*
* ====================================================================
*
* This software consists of voluntary contributions made by many individuals
* on behalf of Project JXTA. For more information on Project JXTA, please see
* http://www.jxta.org.
*
* This license is based on the BSD license adopted by the Apache Foundation.
*/
package net.jxta.platform;
import net.jxta.document.Advertisement;
import net.jxta.exception.PeerGroupException;
import net.jxta.id.ID;
import net.jxta.peergroup.PeerGroup;
/**
* Defines the interface for modules loaded by PeerGroups. Message transports,
* services and applications need to implement this interface if they are
* to be loaded and started by a PeerGroup. Service and Application extend
* Module, PeerGroup implements Service and ShellApp implements Application, as
* a result both implement Module.
*
* <p/>Jxta Modules are given their initialization parameters via the init()
* method rather than a non-default constructor.
*
* <p/>Modules are passed the peer group within which they are created.
* From the peergroup object, Modules can access all the peer group
* services. The PeerGroup within which a PeerGroup runs is known as its
* parent.
*
* <p/>The initial root peer group is known as the World Peer Group and is
* implemented by an object of class Platform, a subclass of PeerGroup.
* The "parent" PeerGroup of the World Peer Group is null.
*
* @see net.jxta.protocol.ModuleImplAdvertisement
* @see net.jxta.platform.ModuleClassID
* @see net.jxta.peergroup.PeerGroup
* @see net.jxta.document.Advertisement
* @see net.jxta.id.ID
* @see net.jxta.platform.Application
* @see net.jxta.service.Service
**/
public interface Module {
/**
* <code>startApp()</code> completed successfully. This module claims to now
* be fully functional and no further invocation of startApp is required.
**/
public static final int START_OK = 0;
/**
* This is to be used mostly by co-dependent services when started as
* a set (such as {@link PeerGroup} services) so that their
* <code>startApp()</code> method may be invoked multiple times.
*
* <p/>This value indicates that startApp must be retried later in order for
* this module to become fully functional. However, some progress in
* functionality was accomplished.
*
* <p/>This is a strong indication that some other modules may be able
* to advance or complete their initialization if their
* <code>startApp()</code> method is invoked again.
*
* <p/>The distinction between START_AGAIN_STALLED and START_AGAIN_PROGRESS
* is only a hint. Each module makes an arbitrary judgment in this
* respect. It is up to the invoker of startApp to ensure that the
* starting of a set of modules eventually succeeds or fails.
**/
public static final int START_AGAIN_PROGRESS = 1;
/**
* This is to be used mostly by co-dependent services when started as
* a set (such as {@link PeerGroup} services) so that their startApp
* method may be invoked multiple times.
*
* <p/>This value indicates that startApp must be retried later in order for
* this module to become fully functional. However, some progress in
* functionality was accomplished.
*
* <p/>If all modules in a set return this value, it is a strong indication
* that the modules co-dependency is such that it prevents them
* collectively from starting.
*
* <p/>The distinction between START_AGAIN_STALLED and START_AGAIN_PROGRESS
* is only a hint. Each module makes an arbitrary judgment in this
* respect. It is up to the invoker of startApp to ensure that the
* starting of a set of modules eventually succeeds or fails.
**/
public static final int START_AGAIN_STALLED = 2;
/**
* This return result is used to indicate that the module refuses to start
* because it has been configured to be disabled or otherwise cannot run
* (missing hardware, missing system resources, etc.) The module will not be
* functional and should be discarded but the failure to load may be ignored
* by the loader at it's discretion.
*/
public static final int START_DISABLED = Integer.MIN_VALUE + 100;
/**
* Initialize the module, passing it its peer group and advertisement.
*
* <p/>Note: when subclassing one of the existing PeerGroup implementations
* (which implement Module), it may not be recommended to overload the init
* method. See the documentation of the PeerGroup class being subclassed.
*
* @param group The PeerGroup from which this Module can obtain services.
* If this module is a Service, this is also the PeerGroup of which this
* module is a service.
*
* @param assignedID Identity of Module within group.
* modules can use it as a the root of their namespace to create
* names that are unique within the group but predictable by the
* same module on another peer. This is normally the ModuleClassID
* which is also the name under which the module is known by other
* modules. For a group it is the PeerGroupID itself.
* The parameters of a service, in the Peer configuration, are indexed
* by the assignedID of that service, and a Service must publish its
* run-time parameters in the Peer Advertisement under its assigned ID.
*
* @param implAdv The implementation advertisement for this
* Module. It is permissible to pass null if no implementation
* advertisement is available. This may happen if the
* implementation was selected by explicit class name rather than
* by following an implementation advertisement. Modules are not
* required to support that style of loading, but if they do, then
* their documentation should mention it.
*
* @exception PeerGroupException This module failed to initialize.
**/
public void init(PeerGroup group, ID assignedID, Advertisement implAdv) throws PeerGroupException;
/**
* Complete any remaining initialization of the module. The module should
* be fully functional after <code>startApp()</code> is completed. That is
* also the opportunity to supply arbitrary arguments (mostly to
* applications).
*
* <p/>If this module is a {@link PeerGroup} service, it may be invoked
* several times depending on its return value.
*
* @param args An array of Strings forming the parameters for this
* Module.
*
* @return int A status indication which may be one of
* {@link #START_OK}, {@link #START_AGAIN_PROGRESS},
* {@link #START_AGAIN_STALLED}, which indicates partial or complete
* success, or any other value (negative values are
* recommended for future compatibility), which indicates failure.
**/
public int startApp(String[] args);
/**
* Stop a module. This may be called any time after <code>init()</code>
* completes and should not assume that <code>startApp()</code> has been
* called or completed.
*
* <p/>The Module cannot be forced to comply, but in the future
* we might be able to deny it access to anything after some timeout.
**/
public void stopApp();
}