Saturday, September 25, 2010

Apache log4j

Apache log4j is a very popular framework for building logging facilities in Java applications. Logging is essential in debugging, localizing problems, and security auditing. Logging statements in the application do not have to be removed when the application is finished for deployment, and will not influence performance.

Log4j is an hierarchical logger, and has 6 logging levels to control/grade logging messages:

  1. TRACE
  2. DEBUG
  3. INFO
  5. ERROR
  6. FATAL

The list is ordered by importance, where the last level is the highest in hierarchy. The current log level and hierarchy determine what to log. When a certain log level is used in an application, all lower ranked log statements are also logged. Example: when the current log level is WARNING, all lower log statements like: TRACE, DEBUG, and INFO are logged. But when the log level is TRACE, no other log level messages will be printed, because the DEBUG level is the lowest log level. Log level can be changed during run-time.

Another control mechanism for hierarchical logging, is that classes/objects of the application obtain a logger separately attached to its class hierarchy. Like the statement below in the constructor of Foo.class.

Log log = Logger.getLogger(Foo.class);

This way, you can configure the logger to print log messages of a selection of classes only. You can use the root logger to print log messages from all classes, or use a class specific logger to print only message from this class and/or its children.

Apache log4j can be configured in two ways:

  1. Using property files (example:
  2. Using XML files (example: log4j.xml)

I prefer the properties file way, because it's less verbose. We can configure many things in the configuration file, like:

  • output log file
  • log file name pattern
  • initial log level
  • log line format
  • log file management

Example application
Let's create an example application that uses Apache log4j:

package test;

import org.apache.log4j.Logger;

public class LogMain {
private Logger log;

public static void main(String[] args) {
LogMain app = new LogMain();;

public LogMain() {
System.out.print("Application started.\n");
this.log = Logger.getLogger(LogMain.class);

public void run() {
this.log.trace("TRACE message!");
this.log.debug("DEBUG message!");"INFO message!");
this.log.warn("WARN message!");
this.log.error("ERROR message!");
this.log.fatal("FATAL message!");

To configure Apache log4j, you can use a properties file or an XML file. The properties file looks like this:

log4j.rootLogger=INFO, CONSOLE, FILE

.conversionPattern=%d{HH:mm:ss:SSS} - %p - %C{1} - %m%n

.conversionPattern=%d{HH:mm:ss:SSS} - %p - %C{1} - %m%n

The equivalent XML-file is this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">


<appender name="file"
<param name="file" value="logs/app.log" />
<param name="datePattern" value="yyyyMMDD." />
<param name="append" value="true" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern"
value="%d{HH:mm:ss:SSS} - %p - %C{1} - %m%n" />

<appender name="console"
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern"
value="%d{HH:mm:ss:SSS} - %p - %C{1} - %m%n" />

<priority value="info" />
<appender-ref ref="console" />
<appender-ref ref="file" />


Put the file in the class path, and Apache log4j will automatically find and load it.

The example configuration uses two log appenders that define the output of logging messages:

  1. DailyRollingFileAppender: automatically rotates logs every day
  2. Console: prints to console

The output can also be customized by the layout class, which is configured to use a conversion pattern to format the output. The output of the example is formatted like this:

19:23:54:938 - WARN - LogMain - WARN message!

This blog post gives you enough information to start using Apache log4j. For more information you can also read the manual here.

Extra note
When using Apache log4j for applications in containers (web and EJB), it might clash with the logging used by the container. For example: Oracle Application Server (OAS) also uses Apache log4j for its application server logging, and will not deploy applications that bundle Apache log4j. This problem can be circumvented by disabling the library apache.commons.logging for deployment.

Sunday, September 19, 2010

SUN certificates rebranded to Oracle

Oracle has rebranded SUN certificates to Oracle certificates.

Click this link to see how the SUN certification titles have been rebranded under the Oracle certification program.

What this means:

  • SUN certificates you're holding will still be valid, and will not expire.
  • Exam objectives remain unchanged for current certification exams.
  • Candidates who pass the exam after 1-3 september 2010 will get the Oracle branded certificate.

Glassfish integration in Eclipse 3.6 (Helios)

Developing in Eclipse for Glassfish is easier when Glassfish is integrated into the IDE. This way, it's possible to right-click the project to deploy the selected project automatically in Glassfish.

In this tutorial, I will show you how to integrate a local Glassfish installation into Eclipse 3.6 (Helios). Before we start, I assume you've installed: Eclipse 3.6, the Java RE, the Java JDK, and the Java EE SDK. Install Java RE and JDK first, before you install the Java SDK.

The first step is to start up Eclipse and locate the servers tab, which is found at the bottom of the screen for default installations.

Now, right-click somewhere in the tab, select "new", and then "server". The following screen will pop up, with the default server adapters.

The server adapter for Glassfish is not included by default. So we have to click "Download additional server adapters" to download the server adapter for Glassfish. A screen will pop up with a selection of server adapters. Select "Oracle Glassfish Server Tools", which is the adapter we're looking for.

Click "next" to download and install the server adapter. Restart Eclipse, when the installation is finished. After the restart, the Glassfish server adapter will show up in the list from the servers tab.

Select it, and click next. The next screen lets you configure the server adapter. Select a working JRE environment and select the installation path of your Glassfish application server.

Click next to go to the next screen. If you have set an administrator password during the installation of Glassfish, you have to fill in this password in the form. Otherwise, use the default values and click next to proceed.

The next screen lets you select existing projects to be added to the newly configured server adapter. The screen is empty in this tutorial, because we're using a fresh install.

When the configuration is succesful, you'll see the server adapter in the servers tab. Now, you can start using it by right-clicking on the server.

From this menu, you can:

  • start/stop the server
  • add/remove new projects
  • publish/unpublish projects
  • view the administration console
  • update Glassfish

Have fun playing with Glassfish in Eclipse!

Friday, September 17, 2010

Number of Sun Certified Enterprise Architects (SCEA) in the world

According to this topic, there are over 5900 SCEAs in the world. Below is an incomplete list of the numbers of SCEAs per country.

Argentina: 14
Australia: 107
Austria: 27
Belgium: 52
Brazil: 200
Canada: 435
China: 138
Denmark: 58
Finland: 45
France: 45
Germany: 276
Hong Kong: 146
India: 421
Italy: 46
Netherlands: 142
New Zealand: 28
Norway: 47
Sweden: 72
UK: 348
Uraguay: 1
USA: 2334

Monday, September 6, 2010


SoapUI is a tool that has a lot in common with the tool discussed in my previous blog post. SoapUI also lets you analyze traffic. But this time, it's all about web services traffic like SOAP, and RESTful web services.

One neat feature is importing WSDL-documents in order to create automatic simulation requests. A generated request template can be filled out, before SoapUI sends it to the server. The response of the web service will be nicely printed on the screen for you to analyze. This way, you can easily test or try out your web service.