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/*
* 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.
*
* 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 Gülcü
* */
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 null
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 AppenderSkeleton 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'
close 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 null 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 true.
*/
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.
In configuration files this option is specified by setting the
value of the Threshold option to a level
string, such as "DEBUG", "INFO" and so on.
@since 0.8.3 */
public
void setThreshold(Priority threshold) {
this.threshold = threshold;
}
}