custom-appender.cpp

This example shows how to extend Log4cxx with a new appender.

/*
 * 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.
 */
 
#include <log4cxx/basicconfigurator.h>
#include <log4cxx/appenderskeleton.h>
#include <log4cxx/helpers/stringhelper.h>
#include <log4cxx/xml/domconfigurator.h>
 
namespace LOG4CXX_NS {
 
class NullWriterAppender : public AppenderSkeleton {
public:
    DECLARE_LOG4CXX_OBJECT(NullWriterAppender)
    BEGIN_LOG4CXX_CAST_MAP()
    LOG4CXX_CAST_ENTRY(NullWriterAppender)
    LOG4CXX_CAST_ENTRY_CHAIN(AppenderSkeleton)
    END_LOG4CXX_CAST_MAP()
 
    NullWriterAppender(){}
 
    void close() override{}
 
    bool requiresLayout() const override {
        return false;
    }
 
    void append(const spi::LoggingEventPtr& event, helpers::Pool& p) override {
        // This gets called whenever there is a valid event for our appender.
    }
 
    void activateOptions(helpers::Pool& /* pool */) override {
        // Given all of our options, do something useful(e.g. open a file)
    }
 
    void setOption(const LogString& option, const LogString& value) override {
        if (helpers::StringHelper::equalsIgnoreCase(option,
                                           LOG4CXX_STR("SOMEVALUE"), LOG4CXX_STR("somevalue"))){
            // Do something with the 'value' here.
        }
    }
};
 
IMPLEMENT_LOG4CXX_OBJECT(NullWriterAppender)
 
}
 
int main( int argc, char** argv )
{
    using namespace log4cxx;
 
    xml::DOMConfigurator::configure( "custom-appender.xml" );
 
    LoggerPtr rootLogger = Logger::getRootLogger();
    LoggerPtr nullLogger = Logger::getLogger( "NullLogger" );
 
    LOG4CXX_INFO( rootLogger, "This is some root message" );
    LOG4CXX_INFO( nullLogger, "This message will be discarded" );
}