Log4cxx custom appender

Question

Is it possible to write a custom appender for log4cxx and have it configurable via a properties file (like the built-in appenders)? I\'d prefer doing this without having to

Answer 1

I am adding this answer as the the links in the most rated answer appear to be from an older version. I have created a custom appender using version 1.2.0 following what was done in their SysLogAppender. At a high level you will need to do these steps:

• Create an your own class which inherits their Appender class.
• Implement the pure virtual functions void close() and void append(const spi::InternalLoggingEvent& event)
• Register your appender class with the AppenderFactoryRegistry.

Here is an example class with code for class with the namespace yournamespace::ExampleCustomAppender:

#include 

namespace yournamespace {
    class ExampleCustomAppender : public Appender
    {
    public:
        ExampleCustomAppender(const log4cplus::helpers::Properties & properties);

        // Dtor
        virtual ~ExampleCustomAppender();

        // Methods
        virtual void close();

        /** Register the appender with the factory registry. */
        static void registerAppender();

    protected:
        virtual void append(const spi::InternalLoggingEvent& event);
    };
}

Then the implementation of the methods:

#include 
#include 

namespace yournamespace {

    ExampleCustomAppender::ExampleCustomAppender(const helpers::Properties & properties)
        : Appender(properties)
    {
    // if you want to use properties to configure your object do so here
    }

    ExampleCustomAppender::~ExampleCustomAppender()
    {
    }

    void ExampleCustomAppender::registerAppender()
    {
        log4cplus::spi::AppenderFactoryRegistry & reg
            = log4cplus::spi::getAppenderFactoryRegistry();
        LOG4CPLUS_REG_PRODUCT(reg, "log4cplus::", ExampleCustomAppender, 
            yournamespace::, log4cplus::spi::AppenderFactory);
    }

    void ExampleCustomAppender::close()
    {
        // do anything you need to close the appender
        closed = true;
    }

    // This method does not need to be locked since it is called by
    // doAppend() which performs the locking
    void LoggingCallbackAppender::append(const spi::InternalLoggingEvent& event)
    {
        if (!closed) {
            std::stringstream logOutput;
            layout->formatAndAppend(logOutput, event);
            std::string outputString = logOutput.str();
        }
    }
}

and lastly an example of how it may be used in the configuration file:

log4cplus.rootLogger=INFO, STDOUT, ROLLING, EXAMPLE
// other definitions for STDOUT and ROLLING here and then  ...
log4cplus.appender.EXAMPLE=log4cplus::ExampleCustomAppender
log4cplus.appender.EXAMPLE.layout=log4cplus::PatternLayout
log4cplus.appender.EXAMPLE.layout.ConversionPattern=%d{%m/%d %H:%M:%S} [%t] %-5p %c{2} - %m%n

I did this code by cutting up some other code so it has not been compiled per se in this exact format. Let me know of any issues and I will correct it.