AppenderSkeleton.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;
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.
* <p>
* This class provides the code for common functionality, such as support for threshold filtering and support for
* general filters.
*
* @author Ceki Gülcü
* @since 0.8.1
*/
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;
/**
* Create new instance.
*/
public AppenderSkeleton() {
super();
}
/**
* Create new instance. Provided for compatibility with log4j 1.3.
*
* @param isActive true if appender is ready for use upon construction. Not used in log4j 1.2.x.
* @since 1.2.15
*/
protected AppenderSkeleton(final boolean isActive) {
super();
}
/**
* 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.setNext(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 appender.
*
* @return name, may be null.
*/
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.getNext();
}
}
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;
}
}