What is log4J's equivalent of java.util.logging.Handler - log4j

Question

I like to intercept some (the most important) log messages and display them inside the GUI or check if any errors where logged. Normally I use java.util.logging and here the java.util.logging.Handler with and java.util.logging.Formatter.
However the current project uses Log4J (2.x) and there every feature has different names and seems to be at least four times as complex.
Can anybody give me some hints on how to archive something like this with Log4J:
/**
* <p>
* logs error so they can be returned to the server (and tested in unit tests)
* </p>
*
* #author "Martin Krischik" <martin.krischik#noser.com>
* #version 1.0 $Revision: 2229 $
* #see java.util.logging.Handler
* #since 1.0
*/
#SuppressWarnings ("synthetic-access")
protected final class LogHandler
extends
java.util.logging.Handler
{
/**
* <p>
* A very simple formatter which displays only what is relevant to end users. Developer
* should look at the log file
* </p>
*
* #author "Martin Krischik" <martin.krischik#noser.com>
* #version 1.0 $Revision: 2229 $
* #see java.util.logging.Formatter
* #since 1.0
*/
private class LogFormatter
extends
java.util.logging.Formatter
{
/**
* <p>
* line separator
* </p>
*/
private final String lineSeparator = System.getProperty ("line.separator");
/**
* <p>
* Format the given LogRecord.
* </p>
*
* #param record
* the log record to be formatted.
* #return a formatted log record
* #see java.util.logging.Formatter#format(java.util.logging.LogRecord)
*/
#Override
public synchronized String format (final java.util.logging.LogRecord record)
{
final StringBuilder retval = new StringBuilder (4096);
final String message = this.formatMessage (record);
final java.util.logging.Level level = record.getLevel ();
retval.append (level.getLocalizedName ());
retval.append (": ");
retval.append (message);
retval.append (this.lineSeparator);
return retval.toString ();
} // format
} // LogFormatter
/**
* <p>
* A very simple formatter which displays only what is relevant to end users. Developer
* should look at the log file
* </p>
*/
private final DBUpdate.LogHandler.LogFormatter formatter =
new DBUpdate.LogHandler.LogFormatter ();
/**
* #throws SecurityException
* some severity error
* #see java.util.logging.Handler#close()
*/
#Override
public void close ()
throws SecurityException
{
return;
} // close
/**
* #see java.util.logging.Handler#flush()
*/
#Override
public void flush ()
{
return;
} // flush
/**
* #param record
* record to log.
* #see java.util.logging.Handler#publish(java.util.logging.LogRecord)
*/
#Override
public void publish (final java.util.logging.LogRecord record)
{
if (record.getLevel ().intValue () >= this.getLevel ().intValue ())
{
REST_Responce.this.errorMessages.add (this.formatter.format (record));
} // if
return;
} // publish
} // LogHandler

Answer 1

You could try to subclass AbstractAppender.
Appender maps to Handler
Layout maps to Formatter
ErrorHandler maps to ErrorManager