Logging class to record errors or unexpected behavior to a file : Debug « Development Class « Java

1. Java
2. Development Class
3. Debug

Logging class to record errors or unexpected behavior to a file

    
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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;
  }
}

   
    
    
    
  

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