Java logging questions - an example would really help

Question

We have taken over a project (i.e. we inherited someone else's code). I am relatively new to java. We would like to add debug messages or log messages to trace the application. Is there an easy way to insert debug messages and view the applicable log files?
1.) I added the following code to add a debug message "log.error("Inside doResetPassword (" + userIdentification + ", " + newPassword + ")");"
2.) Where is this log file located (what is the name of the log file)? Do I have to enable logging in Oracle? What are the steps to enable the logging? Is there a console that displays the log messages?
Any help would be greatly appreciated ...
Thanks,
Mike
public class AuthenticationListener implements Listener {
private static final Log log = LogFactory.getLog(AuthenticationListener.class);
PersonnelService personnelService;
EmailService emailService;
* Setter for Spring injection of {@link EmailService}.
* @param emailService
public void setEmailService(EmailService emailService) {
this.emailService = emailService;
* Setter for Spring injection of {@link PersonnelService}.
* @param personnelService
public void setPersonnelService(PersonnelService personnelService) {
this.personnelService = personnelService;
public void doResetPassword(String userIdentification, String newPassword) {
Personnel personnel = personnelService.loadPersonnelById(Integer.parseInt(userIdentification));
log.error("Inside doResetPassword (" + userIdentification + ", " + newPassword + ")");
try {
emailService.send(new PasswordEmail(personnel, newPassword));
} catch (Exception e) {
log.error("AuthenticationListener.doResetPassword: " + e.getMessage());
}

Answer 1

Hi,
You should check out log4j. It's pretty easy to use, and has been the favorite logging tool for pretty much everyone I've worked with for the last few years. It's free, just google it.
You won't have to change your java code, it plugs into the standard Java logging facility automatically.
You just put log4j.jar and log4j.xml into your applib directory. Here is an example of a log4j.xml file that logs both to the console and to the file /logs/my.log. It assumes your code is in 'com.mypackage.' You can have as many logger elements as you want, and have different packages or classes set to different logging levels.
<pre>
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
     <appender name="console" class="org.apache.log4j.ConsoleAppender">
          <param name="Target" value="System.out" />
          <layout class="org.apache.log4j.PatternLayout">
               <param name="ConversionPattern" value="%d{HH:mm:ss,SSS} %-5p %C %m%n" />
          </layout>
     </appender>
     <appender name="file" class="org.apache.log4j.RollingFileAppender">
          <param name="File" value="/logs/my.log" />
     <param name="Append" value="true" />     
          <layout class="org.apache.log4j.PatternLayout">
               <param name="ConversionPattern"
                    value="%d{HH:mm:ss,SSS} %-5p %c %m%n" />
          </layout>
     </appender>
     <logger name="com.mypackage">
          <level value="debug" />
     </logger>
     <root>
          <priority value="warn" />
          <appender-ref ref="console" />
          <appender-ref ref="file" />
     </root>
</log4j:configuration>
</pre>
Hope that helps,
Mike from Ottawa