create new tag
, view all tags
-- JoaoCarreira - 15 Dec 2009

XEO Logging Mechanism

General Description

In XEO a logging system was created to create an abstraction over the loggers currently used. In the current XEO version log4j was updated to release 1.2.15 (which is used internally by the XEO). This Logging system is an attempt in normalizing the logging process in XEO Applications.

If no configuration is specified in the boconfig.xml, the system will use the log4j general parameterization, namely the log4j.properties file.

Logger Architecture

The logger system consists of two levels. The Logger and the Appender

The loggers are the elements that define which packages should be logged, as also the writing format in the log. For each logger there are appenders, which can be the following:

  • console - This appender writes the log messages to the standard Java output
  • file - This appender creates log files with a predefined file-size limit.
  • email - This appender sends error by email to the configured recipients. This logger does not work in every logging level ( only for error levels superior to WARNING).

There can be loggers with different appenders, if you need to have Java packages logged in different ways.

How to use

Obtain a logger for a class

import netgest.bo.system.Logger;
private static final Logger logger = Logger.getLogger(MyClass.class);

Write on the log

logger.warn("Something went wrong. Message");


When logging, you should pay attention to performance. For instance, avoid logging messages if the logger is not active for the current level.

When logging, you should put the code inside an if statement to check if the logger is active for the current level.


logger.finest("Entering class " + this.getClass().getName );


if( logger.isFinestEnabled() ) 
    logger.finest("Entering class %s", this.getClass().getName ); 

In the "Correct" way, you avoid the string to be concatenated with the class name when the FINEST level is not active.

XEO Logging configuration ( boconfig.xml )

Logging levels and respective use cases:

# Level Log Text Description
1 FINEST FINST This level should be used to debug behavior. This level should never be active in production environments.
2 FINER FINER This level should give relevant information to trace errors, ( such as when calling external API's, or reading runtime configuration results.
3 FINE FINE Extended log level, should give information about background task execution, results of external API calls (like sending emails), web service calls, etc.
4 CONFIG CONF Information about System configurations, Attention, do not log passwords.
5 WARNING WARN Information of critical warning, unusual errors, but those the user is notified if they occurred.
6 SEVERE SEVER Errors that prevent a good system functioning, such as poorly written queries, viewers/objects with definition syntax error.

Configuration in boconfig.xml

General configuration logger:

Attribute Possible Values Description
active true/false If the logger is active or not
for String separated by commas Java Packages for which this configuration should be used
level FINEST / FINER / FINE / CONFIG / WARNING / SERVERE Log level that will be used by this configuration
pattern Writing format for the log of type log4j Log writing format

Appender Configuration console:

Attribute Possible Values Description
active true/false Activate or disable this appender

Appender Configuration file:

Attribute Possible Values Description
active true/false Activate or disable this appender


Name of the log file

Path relative to the xeoHome or absolute path (with filename)

maxSize nn / nnKB / nnMB Maximum log file size.
backupFiles n Number of files that should be kept in the history after log limit exceeded

Appender Configuration ( This Appender only works for logs superior to WARNING) email:

Attribute Possible Values Description
active true/false Activate or disable this appender
buffer n Number of earlier messages in the log that should be sent in the email body
smtpHost hostname SMTP Server to use for sending error logs
from email address Sender email address
to email address Receiver email address
cc email address Email CC address
bcc email address Email BCC address
subject String Email subject text
Configuration Examples

This logger is configured to do logging in all classes that are in the pt and netgest package hierarchy. The log level is FINEST so, the log will be long. Since the email appender is deactivated, the WARNING and SEVERE messages are not sent by email.

 <logger active='true' for='pt,netgest' level='FINEST' pattern='%d %5p [%t] (%F:%L) - %m%n' >
  <console active='true'  />
  <file active='true' logFile='.\log\fileName.log' backupFiles='5' maxSize='50MB' />
  <email active='false' buffer='50' smtpHost='mail.itds.pt' from='' to='jp[a]itds.pt' cc='' bcc='' subject='ola' />

The next listing includes different logger and appenders for different Java packages. This configuration makes the log in FINEST mode to the console, file and email of all classes that are in the package pt (remember, though, that e-mail messages are only sent for SEVERE errors). For the classes in the netgest package, only the console logger is enabled (for CONFIG level or higher).

 <logger active='true' for='pt' level='FINEST' pattern='%d %5p [%t] (%F:%L) - %m%n' >
  <console active='true'  />
  <file active='true' logFile='.\log\fileName.log' backupFiles='5' maxSize='50MB' />
  <email active='true' buffer='50' smtpHost='mail.itds.pt' from='' to='destemail' cc='' bcc='' subject='ola' />
 <logger active='true' for='netgest' level='CONFIG' pattern='%d %5p [%t] (%F:%L) - %m%n' >
  <console active='true'  />

Example of a class using logging

package pt.logger;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;

import netgest.bo.system.Logger;
import netgest.bo.system.boApplication;

public class LoggerDemo {
   // Initialize the logger for the class
   private static final Logger logger = Logger.getLogger( LoggerDemo.class );
   public static void main( String[] args ) {
      // Call some sample methods
   public static void doSomeWork() {
      FileWriter fw;
      PrintWriter pw;
      File propsFile;
      // Log configuration info to the logger
      logger.config("xeoHome is [%s]", 
      propsFile = new File("c:\\jvmprops.txt");
      if( propsFile.exists() ) {
         // Warning - the previous file was overwritten
         logger.warn("Overwritting file %s ", propsFile.getName() );
      else {
         if( logger.isFineEnabled() )
            // Fine - Creating a file
            logger.fine("Creating file %s ", propsFile.getName() );
      try {
         fw = new FileWriter( propsFile );
         pw = new PrintWriter( fw );
         if( logger.isFinestEnabled() ) {
            // Finest - Filling a file
            logger.finest("Dumping properties to [%s]", propsFile.getAbsolutePath() );
         for( Object propName : System.getProperties().keySet() ) {
            pw.format( "%s : %s \n", propName, System.getProperty( propName.toString() ) );
         if( logger.isFinestEnabled() ) {
            // Finest - Closing the file
            logger.finest("Closing file [%s]", propsFile.getAbsolutePath() );
      } catch (IOException e) {
         // Severe - Something goes wrong writing the file
         logger.severe( "Error writing to file [%s]" , e, propsFile.getAbsolutePath() );
   public static void loggedMethod() {
      // Finest - tracing method call's
      logger.finest( "Entering in method: %s", "loggedMethod" );
      // Do Work
      // (...)

      logger.finest( "Exiting in method: %s", "loggedMethod" );

Topic attachments
I Attachment Action Size Date Who Comment
Java source code filejava LoggerDemo.java manage 2.1 K 2009-12-21 - 20:49 JoaoCarreira Código fonte da class de demonstração
Topic revision: r8 - 2013-06-07 - PedroRio

No permission to view TWiki.WebTopBar

This site is powered by the TWiki collaboration platform Powered by Perl

No permission to view TWiki.WebBottomBar