Log.java Source code

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Here is the source code for Log.java

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/*BEGIN_COPYRIGHT_BLOCK
 *
 * Copyright (c) 2001-2008, JavaPLT group at Rice University (drjava@rice.edu)
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *    * Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *    * Redistributions in binary form must reproduce the above copyright
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 *      documentation and/or other materials provided with the distribution.
 *    * Neither the names of DrJava, the JavaPLT group, Rice University, nor the
 *      names of its contributors may be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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import java.io.*;

import java.util.Date;
import java.text.SimpleDateFormat;
import java.util.TimeZone;

/** Logging class to record errors or unexpected behavior to a file.  The file is created in the current directory,
  * and is only used if the log is enabled.  All logs can be enabled at once with the ENABLE_ALL field.
  * @version $Id: Log.java 4691 2008-12-02 23:33:27Z dlsmith $
  */
public class Log {
    public static final boolean ENABLE_ALL = false;

    /** Whether this particular log is enabled in development mode. */
    protected volatile boolean _isEnabled;

    /** The filename of this log. */
    protected volatile String _name;

    /** The file object for this log. */
    protected volatile File _file;

    /** PrintWriter to print messages to a file. */
    protected volatile PrintWriter _writer;

    public static final SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("d MMM yyyy H:mm:ss z");
    static {
        DATE_FORMAT.setTimeZone(TimeZone.getTimeZone("GMT"));
        DATE_FORMAT.setLenient(false);
    }

    /** Creates a new Log with the given name.  If enabled is true, a file is created in the current directory with the
      * given name.
      * @param name  File name for the log
      * @param isEnabled  Whether to actively use this log
      */
    public Log(String name, boolean isEnabled) {
        this(new File(name), isEnabled);
    }

    public Log(File f, boolean isEnabled) {
        _file = f;
        _name = f.getName();
        _isEnabled = isEnabled;
        _init();
    }

    /** Creates the log file, if enabled. */
    protected void _init() {
        if (_writer == null) {
            if (_isEnabled || ENABLE_ALL) {
                try {
                    FileWriter w = new FileWriter(_file.getAbsolutePath(), true);
                    _writer = new PrintWriter(w);
                    log("Log '" + _name + "' opened: " + DATE_FORMAT.format(new Date()));
                } catch (IOException ioe) {
                    throw new RuntimeException("Could not create log: " + ioe);
                }
            }
        }
    }

    /** Sets whether this log is enabled.  Only has an effect if the code is in development mode.
      * @param isEnabled  Whether to print messages to the log file
      */
    public void setEnabled(boolean isEnabled) {
        _isEnabled = isEnabled;
    }

    /** Returns whether this log is currently enabled. */
    public boolean isEnabled() {
        return (_isEnabled || ENABLE_ALL);
    }

    /** Prints a message to the log, if enabled.
      * @param message Message to print.
      */
    public synchronized void log(String message) {
        if (isEnabled()) {
            if (_writer == null) {
                _init();
            }
            _writer.println(DATE_FORMAT.format(new Date()) + ": " + message);
            _writer.flush();
        }
    }

    /** Converts a stack trace (StackTraceElement[]) to string form */
    public static String traceToString(StackTraceElement[] trace) {
        final StringBuilder traceImage = new StringBuilder();
        for (StackTraceElement e : trace)
            traceImage.append("\n\tat " + e.toString());
        return traceImage.toString();
    }

    /** Prints a message and exception stack trace to the log, if enabled.
      * @param s  Message to print
      * @param trace  Stack track to log
      */
    public synchronized void log(String s, StackTraceElement[] trace) {
        if (isEnabled())
            log(s + traceToString(trace));
    }

    /** Prints a message and exception stack trace to the log, if enabled.
      * @param s Message to print
      * @param t Throwable to log
      */
    public synchronized void log(String s, Throwable t) {
        if (isEnabled()) {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            t.printStackTrace(pw);
            log(s + "\n" + sw.toString());
        }
    }

    /** Closes a log file. */
    public void close() {
        _writer.close();
        _writer = null;
    }
}