source: trunk/java-utils/src/main/java/de/ugoe/cs/util/console/FileOutputListener.java @ 927

//   Copyright 2012 Georg-August-Universität Göttingen, Germany
//
//   Licensed 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 de.ugoe.cs.util.console;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;

import de.ugoe.cs.util.console.listener.IOutputListener;

/**
 * <p>
 * Implements an {@link IOutputListener} for the {@link Console} that logs all
 * outputs in a file. This can be used to "pipe" the output-stream of the
 * console into a file. The advantage of using this mechanism for piping is that
 * the file will only contain the output stream. No errors, no commands, etc.
 * </p>
 * 
 * @author Steffen Herbold
 * @version 1.0
 */
public class FileOutputListener implements IOutputListener {

        /**
         * <p>
         * Flag that ensures that only one log message is produced if the listener
         * breaks, e.g., because of a full hard disk/quota.
         * </p>
         */
        boolean failureLogged = false;

        /**
         * <p>
         * Name of the output file.
         * </p>
         */
        String filename;

        /**
         * <p>
         * Writer for the output.
         * </p>
         */
        OutputStreamWriter writer = null;

        /**
         * <p>
         * Constructor. Creates a new FileOutputListener.
         * </p>
         * 
         * @param filename
         *            name and path of the file the listener writes to.
         */
        public FileOutputListener(String filename) {
                this.filename = filename;

        }

        /**
         * <p>
         * Starts the listener by opening the file and registering it with the
         * {@link Console}.
         * </p>
         */
        public void start() {
                try {
                        FileOutputStream fos = new FileOutputStream(filename);
                        writer = new OutputStreamWriter(fos, "UTF-8");
                        Console.getInstance().registerOutputListener(this);
                } catch (IOException e) {
                        Console.printerrln("Failed to start FileOutputListener for file "
                                        + filename + ": " + e.getMessage());
                }
        }

        /**
         * <p>
         * Stops the listener by closing the file and removing itself from the
         * {@link Console}.
         * </p>
         */
        public void stop() {
                Console.getInstance().removeOutputListener(this);
                if( writer!=null ) {
                        try {
                                writer.close();
                                writer = null;
                        } catch (IOException e) {
                                Console.printerrln("Failed to close file " + filename + ": "
                                                + e.getMessage());
                        }
                }
        }

        /*
         * (non-Javadoc)
         * 
         * @see
         * de.ugoe.cs.util.console.listener.IOutputListener#outputMsg(java.lang.
         * String)
         */
        @Override
        public void outputMsg(String newMessage) {
                if( writer!=null ) {
                        try {
                                writer.write(newMessage);
                        } catch (IOException e) {
                                if (!failureLogged) {
                                        Console.printerrln("FileOutpustListener for file " + filename
                                                        + " broken: " + e.getMessage());
                                        failureLogged = true;
                                }
                        }
                }
        }

        /**
         * <p>
         * Returns the name of the log file used by this listener.
         * </p>
         * 
         * @return name of the log file
         */
        public String getFilename() {
                return filename;
        }

}