/*
* 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 <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;
}
}
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