log.java

P2P协议GUNTELLA的java源代码

/*
 * Copyright (C) 2000-2001  Ken McCrary
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Email: [e-mail]
 */
package com.kenmccrary.jtella.util;

import java.io.RandomAccessFile;
import java.io.StringWriter;
import java.io.PrintWriter;
import java.io.IOException;

import java.util.Date;

import java.text.DateFormat;


/**
 *  Basic logging
 *
 *
 */
public class Log
{
  private static Log log;
  private static RandomAccessFile logFile;
  private static RandomAccessFile errorFile;

  protected Log()
  {
  }

  /**
   *  Access the log
   *
   */
  public static Log getLog()
  {
    if ( null == log ) 
    {
      log = new Log();
    }

    return log;
  }

  /**
   *  Logs an unexcpected exception, some exceptions, such as IO problems
   *  are to be expected
   *
   */
  public void logUnexpectedException(Throwable t)
  {
    StringWriter stringWriter = new StringWriter();
    t.printStackTrace(new PrintWriter(stringWriter));

    logToError("Exception: \n" + stringWriter.toString());
  }
  
  /**
   *  Logs an exception
   *
   */
  public void log(Throwable t)
  {
    StringWriter stringWriter = new StringWriter();
    t.printStackTrace(new PrintWriter(stringWriter));

    logToDebug("Exception: \n" + stringWriter.toString());
  }


  /**
   *  Logs an error
   *
   */
  public void logError(String txt)
  {
    logToError("ERROR: " + txt);
  }
  
  /**
   *  Logs a warning
   *
   */
  public void logWarning(String txt)
  {
    logToDebug("WARNING: " + txt);
  }

  /**
   *  Logs debug information
   *
   */
  public void logDebug(String txt)
  {
    // TODO whether are not this produces output a system property
    logToDebug("DEBUG: " + txt);
  }

  /**
   *  Logs information
   *
   */
  public void logInformation(String txt)
  {
    logToDebug("INFORMATION: " + txt);
  }

  /**
   *   Writes a log to the error log
   *
   */
  private void logToError(String logString)
  {
    if ( null == errorFile )
    {
      try
      {
        errorFile = new RandomAccessFile("jtella.err", "rw");
        errorFile.seek(errorFile.length());
      }
      catch (Exception io)
      {
        io.printStackTrace();
      }
    }
    
    log(errorFile, logString);
  }

  /**
   *   Writes a log to the debug log
   *
   */
  private void logToDebug(String logString)
  {
    if ( null == System.getProperty("JTella.Debug") )
    {
      // debug mode off
      return;
    }
    
    if ( null == logFile )
    {
      // open file
      try
      {
        logFile = new RandomAccessFile("jtella.log", "rw");
        logFile.seek(logFile.length());
      }
      catch (IOException io)
      {
        io.printStackTrace();
      }        
    }
    
    log(logFile, logString);
  }

  /**
   *  Rights the string to the log
   *
   */
  private void log(RandomAccessFile file, String logString)
  {
    Date date = new Date();
    logString = "[" +
                DateFormat.getDateInstance(DateFormat.SHORT).format(date) + 
                " - " +
                DateFormat.getTimeInstance(DateFormat.FULL).format(date) +
                "] " +
                logString +
                "\r\n";

    try
    {
      synchronized (file)
      {
        file.write(logString.getBytes());
      }
    }
    catch (IOException io)
    {
      io.printStackTrace();
    }
  }
  
  // test
  public static void main(String[] args)
  {
    getLog().logDebug("Test");
  }
}