I have done this for Logback (with plain text only). The basic things you need to do are:
- Implement your own Appender to receive the log events. Log4j 2 provides
AbstractAppender
, which will give you the baseline functionality. - Use an appropriate
Layout
to format the log event (will depend what type ofDocument
you're using for yourJTextPane
. - Append the formatted text to the underlying
Document
for theJTextPane
.
A couple of other points:
- Things will be simpler if you log plain text only, in which case you should use a
JTextArea
. - Presumably you will want to cap the amount of text in the
Document
. You can do this by checking the length on each append and cutting out the first X% usingDocument.remove
when it exceeds the maximum length. - If you have frequent log operations, you should limit the frequency at which you append to the document, and buffer the changes in between to reduce the swing update/repaint overhead. I typically use 3 Hz. This is also advisable when you have multiple log producer threads because although the
Document.insertString
method is thread-safe, it obtains a lock on the document before performing the update and can result in quite a bit of contention.
I'd highly recommend referencing the documentation for this. I've never used Log4j 2, but the documentation looks quite straight forward. Similarly, the "Using Text Components" section of the Java Tutorials provides everything you need to know about the Swing side. Unfortunately I can't provide additional links here.