001    /*
002     * Copyright (C) 2012 eXo Platform SAS.
003     *
004     * This is free software; you can redistribute it and/or modify it
005     * under the terms of the GNU Lesser General Public License as
006     * published by the Free Software Foundation; either version 2.1 of
007     * the License, or (at your option) any later version.
008     *
009     * This software is distributed in the hope that it will be useful,
010     * but WITHOUT ANY WARRANTY; without even the implied warranty of
011     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012     * Lesser General Public License for more details.
013     *
014     * You should have received a copy of the GNU Lesser General Public
015     * License along with this software; if not, write to the Free
016     * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
017     * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
018     */
019    package org.crsh.shell.impl.command.spi;
020    
021    import org.crsh.command.CommandContext;
022    import org.crsh.keyboard.KeyHandler;
023    import org.crsh.stream.Filter;
024    import org.crsh.text.ScreenContext;
025    
026    import java.io.IOException;
027    
028    /**
029     * A command invoker is a filter for a {@link org.crsh.command.CommandContext} kind of consumer.
030     *
031     * @param <C> the consumed element generic type
032     * @param <P> the produced element generic type
033     */
034    public abstract class CommandInvoker<C, P> implements Filter<C, P, CommandContext<? super P>> {
035    
036      /**
037       * Invoke the command.
038       *
039       * @param consumer the consumer for this invocation
040       * @throws IOException any io exception
041       * @throws CommandException anything command exception
042       */
043      public final void invoke(CommandContext<? super P> consumer) throws IOException, CommandException {
044        try {
045          open(consumer);
046        }
047        finally {
048          try {
049            flush();
050          }
051          finally {
052            close();
053          }
054        }
055      }
056    
057      @Override
058      public abstract void flush() throws IOException;
059    
060      @Override
061      public abstract void provide(C element) throws IOException, CommandException;
062    
063      @Override
064      public abstract void open(CommandContext<? super P> consumer) throws IOException, CommandException;
065    
066      @Override
067      public abstract void close() throws IOException, CommandException;
068    
069      /**
070       * Provide an opportunity for the command to implement screen context.
071       *
072       * @return the screen context
073       */
074      public ScreenContext getScreenContext() {
075        return null;
076      }
077    
078      /**
079       * Return the key handler or null if the invoker cannot handler key events.
080       *
081       * @return the key handler
082       */
083      public KeyHandler getKeyHandler() {
084        return null;
085      }
086    }