/* * Copyright 1999,2004 The Apache Software Foundation. *  * Licensed 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.spi;import org.apache.log4j.*;import org.apache.log4j.helpers.LogLog;// Contibutors: Mathias Bogaert/**   RootLogger sits at the top of the logger hierachy. It is a   regular logger except that it provides several guarantees.   <p>First, it cannot be assigned a <code>null</code>   level. Second, since root logger cannot have a parent, the   {@link #getChainedLevel} method always returns the value of the   level field without walking the hierarchy.   @author Ceki G&uuml;lc&uuml; */public final class RootLogger extends Logger {  /**     The root logger names itself as "root". However, the root     logger cannot be retrieved by name.  */  public RootLogger(Level level) {    super("root");    setLevel(level);  }  /**     Return the assigned level value without walking the logger     hierarchy.  */  public final Level getChainedLevel() {    return level;  }  /**     Setting a null value to the level of the root logger may have catastrophic     results. We prevent this here.     @since 0.8.3 */  public final void setLevel(Level level) {    if (level == null) {      LogLog.error(        "You have tried to set a null level to root.", new Throwable());    } else {      this.level = level;    }  }}