Adding Other Servlets

One of the sample servlets provided with the Java Servlet Development Kit is called the snoop servlet. It simply dumps out all of the servlet environment information as shown when you click on the JavaSoft link below:

http://jserv.javasoft.com/servlet/SnoopServlet?key=value

We'll show you how to add any servlet to the VolanoChat server's built-in servlet runner by taking you through an example in which we add the snoop servlet to VolanoChat.

Installing the servlet

You install the servlet by placing it in the VolanoChat server's installation directory. For example, to add the snoop servlet, simply place the file SnoopServlet.class in the server's vchat2.0.0 directory so that the servlet runner can find it.

If you do not require a servlet alias or any initialization parameters, you're done. Just invoke the servlet using the servlet runner's port number. If you are currently using a Web browser on the same machine as the VolanoChat server, you could invoke the servlet with something like:

http://localhost:8080/servlet/SnoopServlet

Note that the link above will work only if you actually installed the snoop servlet, you're on the same machine as the VolanoChat server, and you're running its built-in servlet runner on port 8080.

Defining an alias

To set up an alias, add the following line to the properties file of the servlet runner, called servlets.txt by default.

servlet.snoop.code=SnoopServlet

You must restart the VolanoChat server for the new alias to take effect. With the alias defined, you could invoke the snoop servlet with something like:

http://localhost:8080/servlet/snoop

Defining initialization parameters

If the servlet you're adding has any initialization parameters, you add them to the properties file of the servlet runner as well. For example, to add the following two initialization parameters to the snoop servlet:

key1=value1
key2=value2

we simply add an additional line for the snoop servlet to the servlets.txt file, as shown below:

servlet.snoop.code=SnoopServlet
servlet.snoop.initArgs=key1=value1,key2=value2

You must restart the VolanoChat server for the new initialization parameters to take effect. Now when you invoke the snoop servlet with:

http://localhost:8080/servlet/snoop

you will see the initialization parameters listed in the snoop servlet's output page.

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