AgentService.java

/*
 * RHQ Management Platform
 * Copyright (C) 2005-2014 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */

package org.rhq.core.pc.agent;

import java.io.InputStream;
import java.io.OutputStream;

/**
 * Those plugin container managers that need to expose their interfaces remotely (to the JON Server for example) need to
 * extend this class. This class will know what its remote client interface is (see the constructor) and will be able
 * notify a set of listeners when it is started and stopped (to presumably tell the listeners that they should remote
 * and "unremote" its client interface).
 */
public abstract class AgentService {
    private final Class clientInterface;
    private final AgentServiceStreamRemoter streamRemoter;

    /**
     * Creates a new {@link AgentService} object.
     *
     * @param clientInterface the client interface that this agent service wants to make remotely accessible to external
     *                        clients
     */
    protected AgentService(Class clientInterface, AgentServiceStreamRemoter streamRemoter) {
        this.clientInterface = clientInterface;
        this.streamRemoter = streamRemoter;
    }

    /**
     * Given any inputstream, this will attempt to remote it using the {@link AgentServiceStreamRemoter stream remoter},
     * , thus providing access to external clients. If there is no remoter available, the same input stream instance
     * passed into this method is returned as-is.
     *
     * <p>If <code>inputStream</code> is <code>null</code>, <code>null</code> is returned.</p>
     *
     * @param  inputStream the input stream to remote
     *
     * @return the input stream possibly wrapped in a remote proxy to enable it for remote access.
     */
    protected InputStream remoteInputStream(InputStream inputStream) {
        if ((inputStream == null) || (streamRemoter == null)) {
            return inputStream;
        }
        return streamRemoter.prepareInputStream(inputStream);
    }

    /**
     * Given any outputstream, this will attempt to remote it using the {@link AgentServiceStreamRemoter stream remoter},
     * thus providing access to external clients. If there is no remoter available, the same output stream instance
     * passed into this method is returned as-is.
     *
     * <p>If <code>outputStream</code> is <code>null</code>, <code>null</code> is returned.</p>
     *
     * @param  outputStream the output stream to remote
     *
     * @return the output stream possibly wrapped in a remote proxy to enable it for remote access.
     */
    protected OutputStream remoteOutputStream(OutputStream outputStream) {
        if ((outputStream == null) || (streamRemoter == null)) {
            return outputStream;
        }
        return streamRemoter.prepareOutputStream(outputStream);
    }

    /**
     * Returns the interface that this agent service wants to be made remotely accessible to external clients. In other
     * words, this is the interface the agent will expose as the service's remote POJO interface.
     *
     * @return the interface that should be remoted so external clients can access it
     */
    public Class getClientInterface() {
        return clientInterface;
    }

    /**
     * Returns the stream remoter.
     */
    protected AgentServiceStreamRemoter getStreamRemoter() {
        return streamRemoter;
    }
}