FileLogger.java

package org.apache.maven.shared.scriptinterpreter;

/*
 * 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.
 */

import org.apache.maven.plugin.logging.Log;
import org.apache.maven.shared.utils.io.IOUtil;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;

/**
 * @version $Id$
 */
public class FileLogger
    implements ExecutionLogger
{

    /**
     * The path to the log file.
     */
    private File file;

    /**
     * The underlying file stream this logger writes to.
     */
    private PrintStream stream;

    /**
     * A flag whether the output stream should be closed during finalization of this logger.
     */
    private boolean shouldFinalize = true;

    /**
     * The optional mojo logger to additionally write messages to, can be <code>null</code>.
     */
    private final Log log;

    /**
     * Creates a new logger that writes to the specified file.
     * 
     * @param outputFile The path to the output file, must not be <code>null</code>.
     * @throws java.io.IOException If the output file could not be created.
     */
    public FileLogger( File outputFile )
        throws IOException
    {
        this( outputFile, null );
    }

    /**
     * Creates a new logger that writes to the specified file and optionally mirrors messages to the given mojo logger.
     *
     * @param outputFile The path to the output file, must not be <code>null</code>.
     * @param log The mojo logger to additionally output messages to, may be <code>null</code> if not used.
     * @throws java.io.IOException If the output file could not be created.
     */
    public FileLogger( File outputFile, Log log )
        throws IOException
    {
        this.file = outputFile;
        this.log = log;

        outputFile.getParentFile().mkdirs();
        stream = new PrintStream( new FileOutputStream( outputFile ) );

        Runnable finalizer = new Runnable()
        {
            public void run()
            {
                try
                {
                    finalize();
                }
                catch ( Throwable e )
                {
                    // ignore
                }
            }
        };

        Runtime.getRuntime().addShutdownHook( new Thread( finalizer ) );
    }

    /**
     * Gets the path to the output file.
     * 
     * @return The path to the output file, never <code>null</code>.
     */
    public File getOutputFile()
    {
        return file;
    }

    /**
     * Gets the underlying stream used to write message to the log file.
     * 
     * @return The underlying stream used to write message to the log file, never <code>null</code>.
     */
    public PrintStream getPrintStream()
    {
        return stream;
    }

    /**
     * Writes the specified line to the log file and optionally to the mojo logger.
     * 
     * @param line The message to log.
     */
    public void consumeLine( String line )
    {
        stream.println( line );
        stream.flush();

        if ( log != null )
        {
            log.info( line );
        }
    }

    /**
     * Closes the underlying file stream.
     */
    public void close()
    {
        if ( stream != null )
        {
            stream.flush();
        }

        IOUtil.close( stream );
    }

    /**
     * Closes the underlying file stream.
     */
    protected void finalize()
    {
        if ( shouldFinalize )
        {
            close();
        }
    }
}