log.java

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/* Log.java

{{IS_NOTE

	Purpose: The logging utilities
	Description:
	History:
	2001/11/07 14:55:06, Create, Tom M. Yeh.
}}IS_NOTE

Copyright (C) 2001 Potix Corporation. All Rights Reserved.

{{IS_RIGHT
	This program is distributed under GPL Version 2.0 in the hope that
	it will be useful, but WITHOUT ANY WARRANTY.
}}IS_RIGHT
*/
package org.zkoss.util.logging;

import java.util.logging.Logger;
import java.util.logging.LogManager;
import java.util.logging.Level;
import java.util.logging.Handler;

import org.zkoss.lang.D;
import org.zkoss.lang.Objects;
import org.zkoss.lang.Exceptions;
import org.zkoss.mesg.Messages;

/**
 * The I3 logger. Usage:
 *
 * <p><code>private static final Log log = Log.lookup(MyClass.class);<br>
 * ...<br>
 * if (log.debugable()) log.debug("the information to log:"+some);</code>
 *
 * <p>{@link Log} is designed to minimize the memory usage by avoiding
 * unnecessary allocation of java.util.logging.Logger.
 * In additions, it is possible to use different logger, e.g., log4j,
 * without affecting the client codes.
 * 
 * <p>Since this object is very light-weight, it is OK to have
 * the following statement without using it.<br>
 * private static final Log log = Log.lookup(MyClass.class);
 *
 * <p>To log error or warning, simple use the error and warning method.
 *
 * <p>To log info, depending on the complexity you might want to test infoable
 * first.<br>
 * <pre><code>log.info("a simple info");
 *if (log.infoable())
 *  log.info(a + complex + string + operation);</code></pre>
 *
 * <p>To log debug information, we usually also test with D.<br>
 * <pre><code>log.debug("a simple info");
 *if (D.ON && log.debugable())
 *  log.debug(a + complex + string + operation);</code></pre>
 *
 * <p>There is a special level called FINER whose priority is lower than DEBUG.
 * It is generally used
 * to log massive debug message under certain situation. In other words,
 * it is suggested to use the debug methods to log messages as follows:
 *
 * <pre><code>if (log.finerable()) {
 *  ... do massive testing and/or printing (use finer)
 *}</code></pre>
 *
 * @author tomyeh
 */
public class Log {
	/* Don't interfere what a developer might configure its system
	static {
		if (D.ON) {
			Log.class.getClassLoader().setDefaultAssertionStatus(true);
			Thread.currentThread().getContextClassLoader()
				.setDefaultAssertionStatus(true);
		}
	}*/

	/** All levels. */
	public static final Level ALL     = Level.ALL;
	/** The ERROR level. */
	public static final Level ERROR   = Level.SEVERE;
	/** The WARNING level. */
	public static final Level WARNING = Level.WARNING;
	/** The INFO level. */
	public static final Level INFO    = Level.INFO;
	/** The DEBUG level. */
	public static final Level DEBUG   = Level.FINE;
	/** The FINER level. */
	public static final Level FINER  = Level.FINER;

	/** The category that this log belongs.
	 * Note: it is temporay and set to null when {@link #logger} is called.
	 */
	private String _name;

	/**
	 * Gets the I3 logger based on the class.
	 * @param cls the class that identifies the logger.
	 */
	public static final Log lookup(Class cls) {
		return new Log(cls.getName());
	}
	/**
	 * Gets the I3 logger based on the giving name.
	 */
	public static final Log lookup(String name) {
		return new Log(name);
	}
	/** Gets the I3 logger based on the package.
	 */
	public static final Log lookup(Package pkg) {
		return new Log(pkg.getName());
	}

	/**
	 * The constructor.
	 */
	protected Log(String name) {
		if (name == null)
			throw new IllegalArgumentException(name);
		_name = name;
	}

	/** Returns the name of this logger.
	 */
	public final String getName() {
		return _name;
	}

	/** Returns the logger (never null).
	 * <p>If not found, it created a new one.
	 */
	private final Logger getLogger() {
		return Logger.getLogger(_name);
			//NOTE: we don't cache getLogger because Tomcat use one
			//LogManager per Web app
	}
	/** Returns the closest logger that has been created (never null).
	 */
	private final Logger getClosestLogger() {
		final LogManager logman = LogManager.getLogManager();
		int j = _name.length();
		do {
			final Logger logger = logman.getLogger(_name.substring(0, j));
			if (logger != null)
				return logger;
			j = _name.lastIndexOf('.', j - 1);
		} while (j >= 0);
		return Logger.getLogger("");
	}
	/** Returns the logger, or null if not created yet.
	 */
	private final Logger getLoggerIfAny() {
		return LogManager.getLogManager().getLogger(_name);
	}

	/**
	 * Retruns the logging level.
	 */
	public final Level getLevel() {
		final Logger logger = getLoggerIfAny();
		return logger != null ? logger.getLevel(): null;
	}
	/**
	 * Sets the logging level.
	 */
	public final void setLevel(Level level) {
		getLogger().setLevel(level);
	}

	/**
	 * Tests whether the {@link #WARNING} level is loggable.
	 */
	public final boolean warningable() {
		return getClosestLogger().isLoggable(WARNING);
	}
	/**
	 * Tests whether the {@link #INFO} level is loggable.
	 */
	public final boolean infoable() {
		return getClosestLogger().isLoggable(INFO);
	}
	/**
	 * Tests whether the {@link #DEBUG} level is loggable.
	 */
	public final boolean debugable() {
		return getClosestLogger().isLoggable(DEBUG);
	}
	/**
	 * Tests whether the {@link #FINER} level is loggable.
	 */
	public final boolean finerable() {
		return getClosestLogger().isLoggable(FINER);
	}

	/**
	 * Logs a message and a throwable object at the giving level.
	 *
	 * <p>All log methods eventaully invokes this method to log messages.
	 *
	 * @param t the throwable object; null to ignore
	 */
	public final void log(Level level, String msg, Throwable t) {
		final Logger logger = getClosestLogger();
		if (logger.isLoggable(level)) {
			//We have to unveil the stack frame to find the real source
			//Otherwise, Logger.log will report the wrong source
			//We cannot skip the first few frames because optimizer might
			//preserve all frames
			StackTraceElement[] stack = new Throwable().getStackTrace();
			String cname = "", mname = "";
			for (int j = 0; j < stack.length; ++j) {
				if (!stack[j].getClassName()
				.equals("org.zkoss.util.logging.Log")) {
					cname = stack[j].getClassName();
					mname = stack[j].getMethodName() + ':'
						+ stack[j].getLineNumber();
					break;
				}
			}

			if (t != null)
				logger.logp(level, cname, mname, msg, t);
			else
				logger.logp(level, cname, mname, msg);
		}
	}
	/**
	 * Logs any object and a throwable object at the giving level.
	 *
	 * @param obj the object whose toString method is called to get the message
	 */
	public final void log(Level level, Object obj, Throwable t) {
		log(level, Objects.toString(obj), t);
	}
	/**
	 * Logs a message and a throwable object at the giving level
	 * by giving a message code and multiple format arguments.
	 *
	 * @param t the throwable object; null to ignore
	 */
	public final void
	log(Level level, int code, Object[] fmtArgs, Throwable t) {
		log(level, Messages.get(code, fmtArgs), t);
	}
	/**
	 * Logs a message and a throwable object at the giving level
	 * by giving a message code and ONE format argument.
	 *
	 * @param t the throwable object; null to ignore
	 */
	public final void log(Level level, int code, Object fmtArg, Throwable t) {
		log(level, Messages.get(code, fmtArg), t);
	}
	/**
	 * Logs a message and a throwable object at the giving level
	 * by giving a message code and NO format argument.
	 *
	 * @param t the throwable object; null to ignore
	 */
	public final void log(Level level, int code, Throwable t) {
		log(level, Messages.get(code), t);
	}

	//-- ERROR --//
	/**
	 * Logs an error message and a throwable object.
	 *
	 * <p>Since error messages hardly happens and are rarely disabled,
	 * there is no method like infoable or debuggable.
	 */
	public final void error(String msg, Throwable t) {
		log(ERROR, msg, t);
	}
	/**
	 * Logs an error message.
	 */
	public final void error(String msg) {
		log(ERROR, msg, null);
	}
	/**
	 * Logs an object, whose toString returns the error message,
	 * and a throwable object.
	 *
	 * @param obj the object whose toString method is called to get the message
	 */
	public final void error(Object obj, Throwable t) {
		log(ERROR, obj, t);
	}
	/**
	 * Logs an object, whose toString returns the error message.
	 *
	 * @param obj the object whose toString method is called to get the message
	 */
	public final void error(Object obj) {
		log(ERROR, obj, null);
	}
	/**
	 * Logs an error throwable object.
	 */
	public final void error(Throwable t) {
		log(ERROR, "", t);
	}
	/**
	 * Logs an error message and a throwable object by giving message code.
	 */
	public final void error(int code, Object[] fmtArgs, Throwable t) {
		log(ERROR, code, fmtArgs, t);
	}
	/**
	 * Logs an error message and a throwable object by giving message code.
	 */
	public final void error(int code, Object fmtArg, Throwable t) {
		log(ERROR, code, fmtArg, t);
	}
	/**
	 * Logs an error message and a throwable object by giving message code.
	 */
	public final void error(int code, Throwable t) {
		log(ERROR, code, t);
	}
	/**
	 * Logs an error message by giving message code.
	 */
	public final void error(int code, Object[] fmtArgs) {
		log(ERROR, code, fmtArgs, null);
	}
	/**
	 * Logs an error message by giving message code.
	 */
	public final void error(int code, Object fmtArg) {
		log(ERROR, code, fmtArg, null);
	}
	/**
	 * Logs an error message by giving message code.
	 */
	public final void error(int code) {
		log(ERROR, code, null);
	}

	//-- WARNING --//
	/**
	 * Logs a warning message and a throwable object.
	 *
	 * <p>Since warning messages are rarely disabled,
	 * there is no method like infoable or debuggable.
	 */
	public final void warning(String msg, Throwable t) {
		log(WARNING, msg, t);
	}
	/**
	 * Logs a warning message.
	 */
	public final void warning(String msg) {
		log(WARNING, msg, null);
	}
	/**
	 * Logs an object, whose toString returns the warning message,
	 * and a throwable object.
	 *
	 * @param obj the object whose toString method is called to get the message
	 */
	public final void warning(Object obj, Throwable t) {
		log(WARNING, obj, t);
	}