Mega Code Archive
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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