/*
* RHQ Management Platform
* Copyright (C) 2005-2008 Red Hat, Inc.
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation version 2 of the License.
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
package org.rhq.enterprise.communications.command.client;
import org.rhq.enterprise.communications.command.Command;
import org.rhq.enterprise.communications.command.CommandResponse;
/**
* Interface defining the generic contract that is used to locate a remote endpoint and communicate with that remote
* endpoint via any remoting framework.
*
* @author John Mazzitelli
*/
public interface RemoteCommunicator {
/**
* Connects this communicator object with the remote endpoint. Once connected, this communicator may send commands
* and receive command responses from the remote endpoint.
*
* @throws Exception if failed to connect to the remote endpoint for any reason
*
* @see #disconnect()
*/
void connect() throws Exception;
/**
* Disconnects this communicator object from the remote endpoint. Once disconnected, this communicator will not be
* able to send commands to the remote endpoint.
*
* <p>Note that the user may later on change its mind and reconnect simply by calling {@link #connect()}.</p>
*/
void disconnect();
/**
* Returns <code>true</code> if this object has established a live connection with the remote endpoint.
*
* @return <code>true</code> if connected to a remote endpoint; <code>false</code> otherise
*/
boolean isConnected();
/**
* Sends the given command to the remote endpoint by utilizing a remoting framework supported by the specific
* communicator implementation. This will transport the command to the remote endpoint. This is the method in which
* subclasses make the command-specific client calls necessary to invoke the command on the remote endpoint.
*
* If an error is detected by this method, and a {@link #setFailureCallback(FailureCallback) failure callback}
* is defined, this method will notify that callback of the problem and ask it if it should retry.
*
* @param command encapsulates the command that is to be executed (must not be <code>null</code>)
*
* @return the command response
*
* @throws Throwable on any error (either during the sending or execution of the command)
*/
CommandResponse send(Command command) throws Throwable;
/**
* This is the same as {@link #send(Command)} except, on error, this method will not attempt
* to call the failure callback, if one was set. This is useful when the caller wants to
* explicitly handle any failure that might occur without any interference with a failure callback.
* This method will also not attempt to call the {@link #getInitializeCallback() initialize callback},
* thus allowing this method to be called from the initialize callback itself.
*
* @param command encapsulates the command that is to be executed (must not be <code>null</code>)
*
* @return the command response
*
* @throws Throwable on any error (either during the sending or execution of the command)
*/
CommandResponse sendWithoutCallbacks(Command command) throws Throwable;
/**
* This is the same as {@link #send(Command)} except this method will not attempt
* to call the {@link #getInitializeCallback() initialize callback},
* thus allowing this method to be called from the initialize callback itself.
*
* @param command encapsulates the command that is to be executed (must not be <code>null</code>)
*
* @return the command response
*
* @throws Throwable on any error (either during the sending or execution of the command)
*/
CommandResponse sendWithoutInitializeCallback(Command command) throws Throwable;
/**
* Returns the failure callback currently configured within this object.
*
* @return the callback (may be <code>null</code>)
*/
FailureCallback getFailureCallback();
/**
* Sets the given failure callback as the one that will be notified when this object sees a comm failure.
* You can pass in <code>null</code> if you don't need this object to notify anything when a failure is detected.
* The callback can be used to reconfigure this communicator and retry the failed message (useful to implement
* failover algorithms).
*
* @param callback the object that listens to failures and may trigger retries (may be <code>null</code>)
*/
void setFailureCallback(FailureCallback callback);
/**
* Returns the initialize callback currently configured within this object.
*
* @return the callback (may be <code>null</code>)
*/
InitializeCallback getInitializeCallback();
/**
* Sets the given initialize callback as the one that will be notified when this object attempts
* to send its very first message after a {@link #connect()}. This allows the callback to perform
* additional initialization procedures prior to the first message getting sent to the remote
* endpoint. The callback is free to send its own messages via {@link #sendWithoutCallbacks(Command)}
* or {@link #sendWithoutInitializeCallback(Command)}.
*
* @param callback
*/
void setInitializeCallback(InitializeCallback callback);
/**
* Returns a string representation of the remote endpoint this communicator is configured to talk to.
*
* @return remote endpoint string
*/
String getRemoteEndpoint();
/**
* Sets the remote endpoint that this communicator object will send commands to.
*
* @param endpoint the new remote endpoint
*
* @throws Exception if the communicator could not point to the new remote endpoint
*/
void setRemoteEndpoint(String endpoint) throws Exception;
}