ShellFactory.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.sshd.server;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Map;

import org.apache.sshd.server.session.ServerSession;

/**
 * This factory is used by SSH server when the client connected requests the creation
 * of a shell.
 *
 *
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public interface ShellFactory {

    /**
     * Create a shell.
     * This method is not supposed to throw any exception.
     * Exceptions should be thrown when calling {@link Shell#start(Environment)}
     * method on the shell to start it.
     *
     * @return the newly create shell
     */
    Shell createShell();

    /**
     * Represents a shell that can be used in an interactive mode to send command.
     * This shell have direct streams, meaning those streams will be provided by the ssh server
     * for the shell to use directy. This interface is suitable for implementing shells in java,
     * rather than using an external process.  For wrapping such processes or using inverted streams,
     * see {@link org.apache.sshd.server.shell.InvertedShellWrapper}.
     */
    public interface Shell {

        /**
         * Set the input stream that can be used by the shell to read input.
         * @param in
         */
        void setInputStream(InputStream in);

        /**
         * Set the output stream that can be used by the shell to write its output.
         * @param out
         */
        void setOutputStream(OutputStream out);

        /**
         * Set the error stream that can be used by the shell to write its errors.
         * @param err
         */
        void setErrorStream(OutputStream err);

        /**
         * Set the callback that the shell has to call when it is closed.
         * @param callback
         */
        void setExitCallback(ExitCallback callback);

        /**
         * Starts the shell.
         * All streams must have been set before calling this method.
         *
         * @param env
         * @throws IOException
         */
        void start(Environment env) throws IOException;

        /**
         * Destroy the shell.
         * This method can be called by the SSH server to destroy the shell because
         * the client has disconnected somehow.
         */
        void destroy();

    }

    /**
     * Interface providing access to the environment map and allowing the registration
     * of listeners for certain signals.
     *
     * TODO: should we use enums for signals to allow using EnumSet or varags for
     *       interesting signals ? 
     *
     * @see Signals
     */
    public interface Environment {

        /**
         * Retrieve the environment map
         * @return the environment map
         */
    	Map<String,String> getEnv();

        /**
         * Add a qualified listener for the specific signal
         * @param signal the signal the listener is interested in
         * @param listener the listener to register
         */
    	void addSignalListener(int signal, SignalListener listener);

        /**
         * Remove a previously registered listener for the specific signal
         * @param signal the signal the listener was interested in
         * @param listener the listener to unregister
         */
    	void removeSignalListener(int signal, SignalListener listener);

        /**
         * Add a global listener
         * @param listener the listener to register
         */
    	void addSignalListener(SignalListener listener);

        /**
         * Remove a previously registered listener
         * @param listener
         */
    	void removeSignalListener(SignalListener listener);
    }

    /**
     * Define a listener to receive signals
     */
    public interface SignalListener {

        /**
         *
         * @param signal
         */
    	void signal(int signal);
    }

    /**
     * Callback used by the shell to notify the SSH server is has exited
     */
    public interface ExitCallback {

        /**
         * Informs the SSH server that the shell has exited
         *
         * @param exitValue the exit value
         */
        void onExit(int exitValue);

    }
    
    /**
     * Interface that can be implemented by a shell to be able to access the
     * server session in which this shell will be used.
     */
    public interface SessionAware {

        /**
         * Set the server session in which this shell will be executed.
         *
         * @param session
         */
        void setSession(ServerSession session);
    }

}