'How to create my own Appender in log4j?

I am new in log4j. Can anyone explain how to create my own Appender? i.e. how to implement the classes and interfaces and how to override it?

javalog4jappender


Solution 1:[1]

If you would like to do some manipulations or decisions you can do it like this:

@Override
protected void append(LoggingEvent event) {
        String message = null;
        if(event.locationInformationExists()){
            StringBuilder formatedMessage = new StringBuilder();
            formatedMessage.append(event.getLocationInformation().getClassName());
            formatedMessage.append(".");
            formatedMessage.append(event.getLocationInformation().getMethodName());
            formatedMessage.append(":");
            formatedMessage.append(event.getLocationInformation().getLineNumber());
            formatedMessage.append(" - ");
            formatedMessage.append(event.getMessage().toString());
            message = formatedMessage.toString();
        }else{
            message = event.getMessage().toString();
        }

        switch(event.getLevel().toInt()){
        case Level.INFO_INT:
            //your decision
            break;
        case Level.DEBUG_INT: 
            //your decision
            break;
        case Level.ERROR_INT:
            //your decision
            break;
        case Level.WARN_INT:
            //your decision
            break;
        case Level.TRACE_INT:
            //your decision
            break;
        default:
            //your decision
            break;
        }
}

Solution 2:[2]

I would like to expend @AgostinoX answer to support pro file configuration and the ability to start and stop the logging capture :

public class StringBufferAppender extends org.apache.log4j.AppenderSkeleton {

    StringBuffer logs = new StringBuffer();
    AtomicBoolean captureMode = new AtomicBoolean(false);

    public void close() {
        // TODO Auto-generated method stub

    }

    public boolean requiresLayout() {
        // TODO Auto-generated method stub
        return false;
    }


    @Override
    protected void append(LoggingEvent event) {
        if(captureMode.get())
            logs.append(event.getMessage());
    }

    public void start()
    {
        //System.out.println("[StringBufferAppender|start] - Start capturing logs");
        StringBuffer logs = new StringBuffer();
        captureMode.set(true);
    }

    public StringBuffer stop()
    {
        //System.out.println("[StringBufferAppender|start] - Stop capturing logs");
        captureMode.set(false);
        StringBuffer data = new StringBuffer(logs);
        logs = null;
        return data;
    }


}

Now all you have to do is to define in in the log4j.property file

log4j.rootLogger=...., myAppender  # here you adding your appendr name
log4j.appender.myAppender=com.roi.log.StringBufferAppender # pointing it to the implementation

than when ever you want to enable it during runtume:

Logger logger = Logger.getRootLogger();
        StringBufferAppender appender = (StringBufferAppender)logger.getAppender("myAppender");
        appender.start();

and while want to stop it:

StringBuffer sb = appender.stop();

Solution 3:[3]

To create a own Appender you just implement the Appender Interface and just override it. And also study this link start log

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Lior
Solution 2 USer22999299
Solution 3 Aleksandr Kravets

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