Tutorials : Building Web Applications Using Servlets and JSP :

A: Compiling & Executing Servlets

Compiling the servlets:

A servlet file has a .java extension , so the FirstServlet servlet will be saved in a file FirstServlet.java. Use your favorite 'javac' compiler to compile the sample servlet (and all other servlets). Make sure that the 'servlets.jar' file is in your 'classpath'. So for example, if you installed Java Web Server and the servlets.jar file is in the directory C:\JavaWebServer2.0\lib\servlets.jar then you can compile the servlet with the following command:

	
"javac -classpath 
	C:\JavaWebServer2.0\lib\servlets.jar FirstServlet.java"

The best environment to test - execute servlets is of-course your web server. The Web server should support running servlets.

You can try Apache with Jserv or any other web server with a servlet engine such as Jrun. If you want to try a new web server, download an evaluation copy of Java Web Server, (comes with built in servlet engine). After you install JWS and start the server, it will start by default at port 8080.

One other option is to download the Java Web Server development Kit from Sun and use it for testing.

Once you have your web server and the servlet engine ready you need to set up the default directory from which the servlets will be 'loaded'. For JWS it is '/servlets' under the JWS directory. So put your compiled servlets in this directory.

Also you need to call the servlet invoker. With JWS the /servlet alias starts the invoker. So to access the 'FirstServlet' servlet under 'servlets' directory use the following URL:

	
http://Your Hostname : Port no /servlet/FirstServlet

For e.g.

	
http://localhost:8080/servlet/FirstServlet

So in this article we saw how to build a simple web application using servlets and JSP. One can build on this and make a lot of improvements to the application. First of all we made a lot of assumptions and did not concentrate on the 'best practices' or performance improvements. Secondly we did not use any database such as a table for storing user id, password etc. That helped us not going into the JDBC details as the database calls and connections with reference to servlets need a special treatment. As servlets are multithreaded by default, (Which you can change if you want), one should consider the possible issues with non-thread safe calls. We will try to cover some of these topics in our next article.

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