Semaphores in Java

What exactly is a semaphore ?
To use the wiki definition:

In computer science, particularly in operating systems, a semaphore is a variable 
or abstract data type that is used for controlling access, by multiple processes, 
to a common resource in a parallel programming or a multi-user environment.

Mapping a Filter directly to a Servlet

I guess we have all used filters in our web projects. The common approach that I have followed is specifying the URL patterns to be intercepted by the filter.

<filter>
    <filter-name>someFilter</filter-name>
    <filter-class>com.filter.SomeFilter</filter-class>
</filter>

<filter-mapping>
    <filter-name>someFilter</filter-name>
    <url-pattern>*.do</url-pattern>
</filter-mapping>

All urls having the .do extension will now pass through the filter. There is also one more way to specify the filter pattern.

Which Log message belongs to which user ?

I created a very simple web application. In it any calls to URLs ending in ".do" reach the below servlet :

Handlers and Interceptors in CXF - Are they related ?

I have been trying out some things in CXF (and also feeling pretty good about it :P ) The other day I needed to modify the message of more than one web service in a common manner. I achieved the same using a CXF interceptor. However another team member did the same task using Handlers. Interestingly Handler is more a part of the JAX-WS vocabulary than Interceptor. So I decided to look at this option too.

Writing Logs to the Database

With loggers we have something called as an Appender. Simply defined an appender is a component responsible  for taking a log request, building the log message in a suitable format and sending it to the output device.