LogLog.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.helpers;

/**
 * This class used to output log statements from within the log4j package.
 *
 * <p>
 * Log4j components cannot make log4j logging calls. However, it is sometimes useful for the user to learn about what
 * log4j is doing. You can enable log4j internal logging by defining the <b>log4j.configDebug</b> variable.
 *
 * <p>
 * All log4j internal debug calls go to <code>System.out</code> where as internal error messages are sent to
 * <code>System.err</code>. All internal messages are prepended with the string "log4j: ".
 *
 * @author Ceki G&uuml;lc&uuml;
 * @since 0.8.2
 */
public class LogLog {

    /**
     * Defining this value makes log4j print log4j-internal debug statements to
     * <code>System.out</code>.
     *
     * <p>
     * The value of this string is <b>log4j.debug</b>.
     *
     * <p>
     * Note that the search for all option names is case sensitive.
     */
    public static final String DEBUG_KEY = "log4j.debug";

    /**
     * Defining this value makes log4j components print log4j-internal debug statements to <code>System.out</code>.
     *
     * <p>
     * The value of this string is <b>log4j.configDebug</b>.
     *
     * <p>
     * Note that the search for all option names is case sensitive.
     *
     * @deprecated Use {@link #DEBUG_KEY} instead.
     */
    public static final String CONFIG_DEBUG_KEY = "log4j.configDebug";

    protected static boolean debugEnabled = false;

    /**
     * In quietMode not even errors generate any output.
     */
    private static boolean quietMode = false;

    private static final String PREFIX = "log4j: ";
    private static final String ERR_PREFIX = "log4j:ERROR ";
    private static final String WARN_PREFIX = "log4j:WARN ";

    static {
        String key = OptionConverter.getSystemProperty(DEBUG_KEY, null);

        if (key == null) {
            key = OptionConverter.getSystemProperty(CONFIG_DEBUG_KEY, null);
        }

        if (key != null) {
            debugEnabled = OptionConverter.toBoolean(key, true);
        }
    }

    /**
     * Allows to enable/disable log4j internal logging.
     */
    static public void setInternalDebugging(boolean enabled) {
        debugEnabled = enabled;
    }

    /**
     * This method is used to output log4j internal debug statements. Output goes to
     * <code>System.out</code>.
     */
    public static void debug(String msg) {
        if (debugEnabled && !quietMode) {
            System.out.println(PREFIX + msg);
        }
    }

    /**
     * This method is used to output log4j internal debug statements. Output goes to
     * <code>System.out</code>.
     */
    public static void debug(String msg, Throwable t) {
        if (debugEnabled && !quietMode) {
            System.out.println(PREFIX + msg);
            if (t != null)
                t.printStackTrace(System.out);
        }
    }

    /**
     * This method is used to output log4j internal error statements. There is no way to disable error statements.
     * Output goes to <code>System.err</code>.
     */
    public static void error(String msg) {
        if (quietMode)
            return;
        System.err.println(ERR_PREFIX + msg);
    }

    /**
     * This method is used to output log4j internal error statements. There is no way to disable error statements.
     * Output goes to <code>System.err</code>.
     */
    public static void error(String msg, Throwable t) {
        if (quietMode)
            return;

        System.err.println(ERR_PREFIX + msg);
        if (t != null) {
            t.printStackTrace();
        }
    }

    /**
     * In quite mode no LogLog generates strictly no output, not even for errors.
     *
     * @param quietMode A true for not
     */
    public static void setQuietMode(boolean quietMode) {
        LogLog.quietMode = quietMode;
    }

    /**
     * This method is used to output log4j internal warning statements. There is no way to disable warning statements.
     * Output goes to <code>System.err</code>.
     */
    public static void warn(String msg) {
        if (quietMode)
            return;

        System.err.println(WARN_PREFIX + msg);
    }

    /**
     * This method is used to output log4j internal warnings. There is no way to disable warning statements. Output goes
     * to <code>System.err</code>.
     */
    public static void warn(String msg, Throwable t) {
        if (quietMode)
            return;

        System.err.println(WARN_PREFIX + msg);
        if (t != null) {
            t.printStackTrace();
        }
    }
}