MinLog/src/com/esotericsoftware/minlog/Log.java

package com.esotericsoftware.minlog;

/**
 * A low overhead, lightweight logging system.
 * @author Nathan Sweet <misc@n4te.com>
 */
public class Log {
	/** No logging at all. */
	static public final int LEVEL_NONE = 6;
	/** Critical errors. The application may no longer work correctly. */
	static public final int LEVEL_ERROR = 5;
	/** Important warnings. The application will continue to work correctly. */
	static public final int LEVEL_WARN = 4;
	/** Informative messages. Typically used for deployment. */
	static public final int LEVEL_INFO = 3;
	/** Debug messages. This level is useful during development. */
	static public final int LEVEL_DEBUG = 2;
	/** Trace messages. A lot of information is logged, so this level is usually only needed when debugging a problem. */
	static public final int LEVEL_TRACE = 1;

	/**
	 * The level of messages that will be logged. Compiling this and the booleans below as "final" will cause the compiler to
	 * remove all "if (Log.info) ..." type statements below the set level.
	 */
	static private int level = LEVEL_TRACE; // Log everything to delegate control to slf4j

	/** True when the ERROR level will be logged. */
	static public boolean ERROR = level <= LEVEL_ERROR;
	/** True when the WARN level will be logged. */
	static public boolean WARN = level <= LEVEL_WARN;
	/** True when the INFO level will be logged. */
	static public boolean INFO = level <= LEVEL_INFO;
	/** True when the DEBUG level will be logged. */
	static public boolean DEBUG = level <= LEVEL_DEBUG;
	/** True when the TRACE level will be logged. */
	static public boolean TRACE = level <= LEVEL_TRACE;

	/**
	 * Sets the level to log. If a version of this class is being used that has a final log level, this has no affect.
	 */
	static public void set (int level) {
		// Comment out method contents when compiling fixed level JARs.
		Log.level = level;
		ERROR = level <= LEVEL_ERROR;
		WARN = level <= LEVEL_WARN;
		INFO = level <= LEVEL_INFO;
		DEBUG = level <= LEVEL_DEBUG;
		TRACE = level <= LEVEL_TRACE;
	}

	static public void NONE () {
		set(LEVEL_NONE);
	}

	static public void ERROR () {
		set(LEVEL_ERROR);
	}

	static public void WARN () {
		set(LEVEL_WARN);
	}

	static public void INFO () {
		set(LEVEL_INFO);
	}

	static public void DEBUG () {
		set(LEVEL_DEBUG);
	}

	static public void TRACE () {
		set(LEVEL_TRACE);
	}

	/**
	 * Sets the logger that will write the log messages.
	 */
	static public void setLogger (Logger logger) {
		Log.logger = logger;
	}

	static private Logger logger = new Logger();

	static public void error (String message, Throwable ex) {
		if (ERROR) logger.log(LEVEL_ERROR, null, message, ex);
	}

	static public void error (String category, String message, Throwable ex) {
		if (ERROR) logger.log(LEVEL_ERROR, category, message, ex);
	}

	static public void error (String message) {
		if (ERROR) logger.log(LEVEL_ERROR, null, message, null);
	}

	static public void error (String category, String message) {
		if (ERROR) logger.log(LEVEL_ERROR, category, message, null);
	}

	static public void warn (String message, Throwable ex) {
		if (WARN) logger.log(LEVEL_WARN, null, message, ex);
	}

	static public void warn (String category, String message, Throwable ex) {
		if (WARN) logger.log(LEVEL_WARN, category, message, ex);
	}

	static public void warn (String message) {
		if (WARN) logger.log(LEVEL_WARN, null, message, null);
	}

	static public void warn (String category, String message) {
		if (WARN) logger.log(LEVEL_WARN, category, message, null);
	}

	static public void info (String message, Throwable ex) {
		if (INFO) logger.log(LEVEL_INFO, null, message, ex);
	}

	static public void info (String category, String message, Throwable ex) {
		if (INFO) logger.log(LEVEL_INFO, category, message, ex);
	}

	static public void info (String message) {
		if (INFO) logger.log(LEVEL_INFO, null, message, null);
	}

	static public void info (String category, String message) {
		if (INFO) logger.log(LEVEL_INFO, category, message, null);
	}

	static public void debug (String message, Throwable ex) {
		if (DEBUG) logger.log(LEVEL_DEBUG, null, message, ex);
	}

	static public void debug (String category, String message, Throwable ex) {
		if (DEBUG) logger.log(LEVEL_DEBUG, category, message, ex);
	}

	static public void debug (String message) {
		if (DEBUG) logger.log(LEVEL_DEBUG, null, message, null);
	}

	static public void debug (String category, String message) {
		if (DEBUG) logger.log(LEVEL_DEBUG, category, message, null);
	}

	static public void trace (String message, Throwable ex) {
		if (TRACE) logger.log(LEVEL_TRACE, null, message, ex);
	}

	static public void trace (String category, String message, Throwable ex) {
		if (TRACE) logger.log(LEVEL_TRACE, category, message, ex);
	}

	static public void trace (String message) {
		if (TRACE) logger.log(LEVEL_TRACE, null, message, null);
	}

	static public void trace (String category, String message) {
		if (TRACE) logger.log(LEVEL_TRACE, category, message, null);
	}

	private Log () {
	}

	/**
	 * Performs the actual logging. Default implementation logs to slf4j. Extended and use {@link Log#logger} set to handle
	 * logging differently.
	 */
	static public class Logger {
		// Log as "com.esotericsoftware.minlog"
		public final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(Logger.class.getPackage().getName());

		public void log (int level, String category, String message, Throwable ex) {
			if (level == LEVEL_NONE) {
				return;
			}
			StringBuilder builder = new StringBuilder(256);
			if (category != null) {
				builder.append(category);
				builder.append(": ");
			}
			builder.append(message);
			String line = builder.toString();

			switch (level) {
				case LEVEL_ERROR: logger.error (line, ex); break;
				case LEVEL_WARN:  logger.warn  (line, ex); break;
				case LEVEL_INFO:  logger.info  (line, ex); break;
				case LEVEL_DEBUG: logger.debug (line, ex); break;
				case LEVEL_TRACE: logger.trace (line, ex); break;
			}
		}
	}
}