/* * Copyright 1999-2005 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;import org.apache.log4j.Layout;import org.apache.log4j.spi.Filter;import org.apache.log4j.spi.ErrorHandler;import org.apache.log4j.spi.OptionHandler;import org.apache.log4j.spi.LoggingEvent;import org.apache.log4j.helpers.OnlyOnceErrorHandler;import org.apache.log4j.helpers.LogLog;/**  * Abstract superclass of the other appenders in the package. *   *  This class provides the code for common functionality, such as *  support for threshold filtering and support for general filters. * * @since 0.8.1 * @author Ceki G&uuml;lc&uuml;  * */public abstract class AppenderSkeleton implements Appender, OptionHandler {  /** The layout variable does not need to be set if the appender      implementation has its own layout. */  protected Layout layout;  /** Appenders are named. */  protected String name;  /**     There is no level threshold filtering by default.  */  protected Priority threshold;  /**       It is assumed and enforced that errorHandler is never null.  */  protected ErrorHandler errorHandler = new OnlyOnceErrorHandler();  /** The first filter in the filter chain. Set to <code>null</code>      initially. */  protected Filter headFilter;  /** The last filter in the filter chain. */  protected Filter tailFilter;  /**     Is this appender closed?    */  protected boolean closed = false;  /**     Derived appenders should override this method if option structure     requires it.  */  public  void activateOptions() {  }  /**     Add a filter to end of the filter list.     @since 0.9.0   */  public  void addFilter(Filter newFilter) {    if(headFilter == null) {      headFilter = tailFilter = newFilter;    } else {      tailFilter.next = newFilter;      tailFilter = newFilter;        }  }  /**     Subclasses of <code>AppenderSkeleton</code> should implement this     method to perform actual logging. See also {@link #doAppend     AppenderSkeleton.doAppend} method.     @since 0.9.0  */  abstract  protected  void append(LoggingEvent event);  /**     Clear the filters chain.          @since 0.9.0 */  public  void clearFilters() {    headFilter = tailFilter = null;  }  /**     Finalize this appender by calling the derived class'     <code>close</code> method.     @since 0.8.4 */  public  void finalize() {    // An appender might be closed then garbage collected. There is no    // point in closing twice.    if(this.closed)       return;    LogLog.debug("Finalizing appender named ["+name+"].");    close();  }  /**       Return the currently set {@link ErrorHandler} for this      Appender.        @since 0.9.0 */  public  ErrorHandler getErrorHandler() {    return this.errorHandler;  }  /**     Returns the head Filter.          @since 1.1  */  public  Filter getFilter() {    return headFilter;  }  /**       Return the first filter in the filter chain for this      Appender. The return value may be <code>null</code> if no is      filter is set.        */  public  final  Filter getFirstFilter() {    return headFilter;  }  /**     Returns the layout of this appender. The value may be null.  */  public  Layout getLayout() {    return layout;  }  /**     Returns the name of this FileAppender.   */  public  final  String getName() {    return this.name;  }  /**     Returns this appenders threshold level. See the {@link     #setThreshold} method for the meaning of this option.          @since 1.1 */  public  Priority getThreshold() {    return threshold;  }  /**     Check whether the message level is below the appender's     threshold. If there is no threshold set, then the return value is     always <code>true</code>.  */  public  boolean isAsSevereAsThreshold(Priority priority) {    return ((threshold == null) || priority.isGreaterOrEqual(threshold));  }  /**    * This method performs threshold checks and invokes filters before    * delegating actual logging to the subclasses specific {@link    * AppenderSkeleton#append} method.    * */  public  synchronized   void doAppend(LoggingEvent event) {    if(closed) {      LogLog.error("Attempted to append to closed appender named ["+name+"].");      return;    }        if(!isAsSevereAsThreshold(event.getLevel())) {      return;    }    Filter f = this.headFilter;        FILTER_LOOP:    while(f != null) {      switch(f.decide(event)) {      case Filter.DENY: return;      case Filter.ACCEPT: break FILTER_LOOP;      case Filter.NEUTRAL: f = f.next;      }    }        this.append(event);      }  /**       Set the {@link ErrorHandler} for this Appender.      @since 0.9.0  */  public  synchronized  void setErrorHandler(ErrorHandler eh) {    if(eh == null) {      // We do not throw exception here since the cause is probably a      // bad config file.      LogLog.warn("You have tried to set a null error-handler.");    } else {      this.errorHandler = eh;    }  }  /**     Set the layout for this appender. Note that some appenders have     their own (fixed) layouts or do not use one. For example, the     {@link org.apache.log4j.net.SocketAppender} ignores the layout set     here.   */  public  void setLayout(Layout layout) {    this.layout = layout;  }    /**     Set the name of this Appender.   */  public  void setName(String name) {    this.name = name;  }  /**     Set the threshold level. All log events with lower level     than the threshold level are ignored by the appender.          <p>In configuration files this option is specified by setting the     value of the <b>Threshold</b> option to a level     string, such as "DEBUG", "INFO" and so on.          @since 0.8.3 */  public  void setThreshold(Priority threshold) {    this.threshold = threshold;  }  }