Question

How to send exception to log4j log from java swing ?

We have much code already done and it does a lot of:

mytable.getSelectionModel().addListSelectionListener(
        new ListSelectionListener() {
            @Override
            public void valueChanged(ListSelectionEvent e) {
                ... no try catch
            }
        });

There is no try/catch. App sends npe exception to console. We need it in log4j. But don’t want to change all this code (100s of line like this). What can we do?

Answer 1

You can set up an uncaught-exception handler that will log anything thrown by your application.

In the main method of your Swing app add these lines:

Thread.setDefaultUncaughtExceptionHandler(new LoggingExceptionHandler());
System.setProperty("sun.awt.exception.handler", LoggingExceptionHandler.class.getName());

Then implement the exception-handler like this:

package com.initech.tps;

import java.lang.Thread.UncaughtExceptionHandler;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class LoggingExceptionHandler implements UncaughtExceptionHandler
{

  private static final Logger logger = LoggerFactory.getLogger(LoggingExceptionHandler.class);

  @Override
  public void uncaughtException(Thread t, Throwable e)
  {
      logger.error("caught exception in thread: " + t.getName(), e);
  }
}