Re: log4j configuration and Applets

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <>
Sun, 07 Jun 2009 15:55:26 -0400
Richard Maher wrote:

I need to do some logging from my Applet with varying levels of verbosity
and log4j looked like the most likely, best-of-breed, widley used, option
available for the right price. (The Applet is unsigned so a Console Appender
to System.out is all I require and have available)

So I downloaded log4j-1_2_15.jar and included it with my HTML <object> and
everything looked ok, but when the Applet loaded it was now instructing the
browser to look for a log4j.xml or log4j.conf file. I thought I was
good-to-code with the default configuration options (plus runtime
configuration of the logging level [info,debug,fatal, etc]) but I was happy
to stick a minimal XML file where the browser could find it. (See below)

What I don't like about it now is it's asking for all sorts of
infrastructure bloat to be resolved and sent down the line: -







I guess I'm asking why these classes (if needed) aren't in the JAR file
already and just home much "baggage" does log4j need?

Is there a "minimalist" switch I can set in the config, or perhaps log4j is
not the most appropriate tool after all?

I have no idea about where those classes come from. But I do
not think they are needed.

See simple example below, which works for me.

I use instead of log4j.xml, but that should
not matter.



Jar content

      0 Sun Jun 07 15:48:38 EDT 2009 META-INF/
     97 Sun Jun 07 15:48:38 EDT 2009 META-INF/MANIFEST.MF
    799 Sun Jun 07 15:33:08 EDT 2009 test/LogApplet$1.class
    798 Sun Jun 07 15:33:08 EDT 2009 test/LogApplet$2.class
    798 Sun Jun 07 15:33:08 EDT 2009 test/LogApplet$3.class
    799 Sun Jun 07 15:33:08 EDT 2009 test/LogApplet$4.class
   1302 Sun Jun 07 15:33:08 EDT 2009 test/LogApplet$5.class
   1291 Sun Jun 07 15:33:08 EDT 2009 test/LogApplet$6.class
   2216 Sun Jun 07 15:33:08 EDT 2009 test/LogApplet.class
   2947 Sun Jun 07 15:48:34 EDT 2009 test/GuiAppender.class
    487 Sun Jun 07 15:31:40 EDT 2009


Class-Path: log4j-1.2.9.jar

package test;

import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JApplet;
import javax.swing.JButton;

import org.apache.log4j.ConsoleAppender;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public class LogApplet extends JApplet {
     private Logger log = Logger.getLogger(LogApplet.class);
     private JButton debugbtn = new JButton("Log debug");
     private JButton infobtn = new JButton("Log info");
     private JButton warnbtn = new JButton("Log warning");
     private JButton errorbtn = new JButton("Log error");
     private JButton consolebtn = new JButton("Log to console");
     private JButton guibtn = new JButton("Log to GUI");
     private boolean console = false;
     private boolean gui = false;
     public void init() {
         debugbtn.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent e) {
                 log.debug("This is a test");
         infobtn.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent e) {
       "This is a test");
         warnbtn.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent e) {
                 log.warn("This is a test");
         errorbtn.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent e) {
                 log.error("This is a test");
         consolebtn.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent e) {
                 console = !console;
                 ConsoleAppender app =
                 if(console) {
                 } else {
         guibtn.addActionListener(new ActionListener() {
             public void actionPerformed(ActionEvent e) {
                 gui = !gui;
                 GuiAppender app = (GuiAppender)log.getAppender("gui");
                 if(gui) {
                 } else {
         getContentPane().setLayout(new GridLayout(3,2 ));


package test;

import java.awt.BorderLayout;
import java.awt.Color;

import javax.swing.JFrame;
import javax.swing.JTextPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.MutableAttributeSet;
import javax.swing.text.StyleConstants;
import javax.swing.text.StyledDocument;

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

public class GuiAppender extends AppenderSkeleton {
     private JFrame f;
     private JTextPane tp;
     public GuiAppender() {
         f = new JFrame();
         tp = new JTextPane();
         f.getContentPane().setLayout(new BorderLayout());
         f.getContentPane().add(tp, BorderLayout.CENTER);
         f.setSize(600, 400);
     private Color LevelToColor(Level lvl) {
         if(lvl.equals(Level.DEBUG)) {
             return Color.GRAY;
         } else if(lvl.equals(Level.INFO)) {
             return Color.GREEN;
         } else if(lvl.equals(Level.WARN)) {
             return Color.YELLOW;
         } else if(lvl.equals(Level.ERROR)) {
             return Color.RED;
         } else if(lvl.equals(Level.FATAL)) {
             return Color.RED;
         } else {
             return Color.BLACK;

     protected void append(LoggingEvent ev) {
         try {
             StyledDocument doc = tp.getStyledDocument();
             MutableAttributeSet attrs = tp.getInputAttributes();
             StyleConstants.setBackground(attrs, Color.LIGHT_GRAY);
             doc.insertString(doc.getLength(), getLayout().format(ev),
         } catch (BadLocationException e) {
     public void open() {
     public void close() {
     public boolean requiresLayout() {
         return true;

log4j.category.test.LogApplet = debug, console, gui
log4j.appender.console.threshold = off
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern = %-30c %d %-5p %m%n
log4j.appender.gui.threshold = off
log4j.appender.gui = test.GuiAppender
log4j.appender.gui.layout = org.apache.log4j.PatternLayout
log4j.appender.gui.layout.ConversionPattern = %-30c %d %-5p %m%n

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