org.dhatim.util.StdoutToLog4jFilter.java Source code

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Here is the source code for org.dhatim.util.StdoutToLog4jFilter.java

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/*
 * Milyn - Copyright (C) 2006 - 2010
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License (version 2.1) as published
 * by the Free Software Foundation.
 * 
 * This library 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 Lesser General Public License for more details:
 * http://www.gnu.org/licenses/lgpl.txt
 */
package org.dhatim.util;

import java.io.FilterWriter;
import java.io.IOException;
import java.io.Writer;

import org.apache.commons.logging.Log;

/**
 * StoutToLog4jFilter is just a simple FileWriter implementation that 
 * supresses output unless the log4j priority is set to debug.
 * This class in indended to be used with hsql embedded server and to 
 * be used like this:
 * <pre>{@code
 * 
 * Log targetLogger = LogFactory.getLog("org.hsqldb");
 * server.setLogWriter(new PrintWriter(new StdoutToLog4jFilter(server.getLogWriter(), targetLogger)));
 * 
 * }</pre>
 * 
 * @author <a href="mailto:dbevenius@redhat.com">Daniel Bevenius</a>
 */
public class StdoutToLog4jFilter extends FilterWriter {
    /**
     * Log to log check logging level.
     */
    protected Log logger;

    /**
     * string "buffer"
     */
    protected StringBuilder sb = new StringBuilder();

    /**
     * Carrage Return
     */
    private static final char CR = '\r';
    /**
     * Line Feed
     */
    private static final char LF = '\n';

    public StdoutToLog4jFilter(Writer writer) {
        super(writer);
    }

    public StdoutToLog4jFilter(Writer writer, Log log) {
        this(writer);
        this.logger = log;
    }

    @Override
    public synchronized void write(int c) throws IOException {
        sb.append(c);
    }

    @Override
    public synchronized void write(char[] cbuf, int off, int len) throws IOException {
        sb.append(cbuf, off, len);
    }

    @Override
    public synchronized void write(String str, int off, int len) throws IOException {
        sb.append(str.substring(off, off + len));
    }

    @Override
    public synchronized void flush() throws IOException {
        log();
    }

    @Override
    public synchronized void close() throws IOException {
        if (sb.length() != 0) {
            log();
        }
    }

    @Override
    protected void finalize() throws Throwable {
        if (sb.length() != 0) {
            log();
        }
        super.finalize();
    }

    protected void log() {
        stripExtraNewLine();
        logBuffer(sb);
        sb.delete(0, sb.length());
    }

    private void logBuffer(final StringBuilder sb) {
        if (logger == null) {
            return;
        }

        if (logger.isDebugEnabled()) {
            logger.debug(sb.toString());
        }
    }

    protected final void stripExtraNewLine() {
        int length = sb.length();

        if (length == 0) {
            return;
        }

        if (length == 1) {
            char last = sb.charAt(0);
            if (last == CR || last == LF) {
                sb.deleteCharAt(0);
            }
        } else {
            int lastPosition = length - 1;
            char secondLast = sb.charAt(lastPosition);
            if (secondLast == CR) {
                sb.deleteCharAt(lastPosition);
            } else if (secondLast == LF) {
                int secondlastPosition = length - 2;
                sb.deleteCharAt(lastPosition);
                if (sb.charAt(secondlastPosition) == CR) {
                    sb.deleteCharAt(secondlastPosition);
                }
            }
        }
    }
}