Log4net and Winsor Container Integration

Inversion of Control / Depedency Injection has been floating around for several years and I got to know this design pattern through the following articles on MSDN website:

• Inversion of Control and Dependency Injection: Working with Windsor Container by Oren Eini
• Dependency Injection by Griffin Caprio

I immediately decided to adopt the pattern into my projects. I chose Castle project's Winsor container for the project I was working on. As soon as I started using Winsor container, I realized how many depedencies my program relied on implictly, especially the log4net object I had instantiated in almost every class. Following the practices recommended by Castle project, I changed the logging object as a property of a class so that Winsor container could inject the logging facility into my object at runtime.

However, my program threw out exceptions when launched. The exception message said there is a revision number mismatch in the log4net library. That is, the Winsor library I used, which is "RC2 for .NET framework 1.1", expects log4net in version 1.2.9.0, but my project referenced the log4net in 1.2.0. That caused the problem. Actually, Visual Studio gave me the warning during compiliation but I didn't notice. After I updated my log4net program reference to version 1.2.9.0, my program worked as expected and I externalized the logging dependencyin my program. That's great.

Do-it-yourself Database Change Notification

I am currently involved in a project which needs some database change notification mechanism. The environment is Oracle 9i + .NET 1.1. Although ADO.NET has this feature, but it's not available in .NET 1.1 and ODP.NET won't support it until version 10.2. So under the current environment, I have to rely on other solutions. Belows are several apporaches I found and I list here for my reference.

1. Use UTL_TCP. With this package, we can write PL/SQL code to communicate with programs out of Oracle database. We write a PL/SQL client using UTL_TCP to send notifications and a socket server, dedicated to listening to the events sent out by the PL/SQL client. If the frontend is an ASP.NET program, UTL_HTTP can be considered as well.
2. Use DBMS_PIPE. This is a package, similar to pipes in Unix, which allow programs to exchange messages. To send and receive notifications, we will write two PL/SQL programs, Publisher and Receiver, using DBMS_PIPE. Change events are sent by calling Publisher and events are received by calling Receiver through ADO.NET. Events are delivered via the pipes Oracle provides.
3. Use Advanced Queuing. This is Oracle's implementation of message queue. I haven't tried it yet, and will post some experience after I have time to give it a try.

Update: If more than 2 sessions need to exchange messages, for DBMS_PIPE to work well, a mechanism is needed to locate the pipes where each communicating session is using. A table might be needed to store the pipe name for each session. It seems DBMS_PIPE is not suitable for a publish/subscribe scenario.