I found a solution, which works.
package com.mypackage;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.log4j.spi.LoggingEvent;
/**
* This HTML Log Formatter is a simple replacement for the standard Log4J HTMLLayout formatter and
* replaces the default timestamp (milliseconds, relative to the start of the log) with a more readable
* timestamp (an example of the default format is 2008-11-21-18:35:21.472-0800).
* */
public class MyLayout
extends org.apache.log4j.HTMLLayout
{
// RegEx pattern looks for <tr> <td> nnn...nnn </td> (all whitespace ignored)
private static final String rxTimestamp = "\\s*<\\s*tr\\s*>\\s*<\\s*td\\s*>\\s*(\\d*)\\s*<\\s*/td\\s*>";
//* The timestamp format. The format can be overriden by including the following
* property in the Log4J configuration file:
*
* log4j.appender.<category>.layout.TimestampFormat
*
* using the same format string as would be specified with SimpleDateFormat.
*
*/
private String timestampFormat = "yyyy-MM-dd-HH:mm:ss.SZ"; // Default format. Example: 2008-11-21-18:35:21.472-0800
private SimpleDateFormat sdf = new SimpleDateFormat(timestampFormat);
public MyLayout()
{
super();
}
/** Override HTMLLayout's format() method */
public String format(LoggingEvent event)
{
String record = super.format(event); // Get the log record in the default HTMLLayout format.
Pattern pattern = Pattern.compile(rxTimestamp); // RegEx to find the default timestamp
Matcher matcher = pattern.matcher(record);
if (!matcher.find()) // If default timestamp cannot be found,
{
return record; // Just return the unmodified log record.
}
StringBuffer buffer = new StringBuffer(record);
buffer.replace(matcher.start(1), // Replace the default timestamp with one formatted as desired.
matcher.end(1),
sdf.format(new Date(event.timeStamp)));
return buffer.toString(); // Return the log record with the desired timestamp format.
}
/** Setter for timestamp format. Called if log4j.appender.<category>.layout.TimestampFormat property is specfied */
public void setTimestampFormat(String format)
{
this.timestampFormat = format;
this.sdf = new SimpleDateFormat(format); // Use the format specified by the TimestampFormat property
}
/** Getter for timestamp format being used. */
public String getTimestampFormat()
{
return this.timestampFormat;
}
}