import java.util.ArrayList;

import org.apache.log4j.AppenderSkeleton;
import org.apache.log4j.spi.LoggingEvent;

public class PayloadLogAppender extends AppenderSkeleton {
    private final ArrayList<LoggingEvent> eventsList = new ArrayList();
    @Override
    protected void append(LoggingEvent event) {
        eventsList.add(event);
    }

    public void close() {
    }
    public boolean requiresLayout() {
        return false;
    }
    public ArrayList<LoggingEvent> getAllMessages() {
        return this.eventsList;
    }
}

log4j.appender.payloadLog=PayloadLogAppender

import mypackage.PayloadLogAppender;

// in the method that gets triggered at the end.
this.LOGGER = Logger.getRootLogger();
Appender payloadlog = this.LOGGER.getAppender("payloadLog");
System.out.println("My list of logging events" + ((PayloadLogAppender) payloadlog).getAllMessage());