Question

I like to know like whenever user requests a jsp page we write hello.jsp or any html file we write hello.html or any image hello.jpeg.
My question is does servlet not have any extension ? Is it called directly called by name?

Answer 1

For Servlets, you have to explicitly tell the Servlet Container what URLs (either specific URLs or wildcards) map to what servlet. For example:

<servlet>
    <servlet-name>HelloWorld</servlet-name>
    <servlet-class>com.example.HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>/hello</url-pattern>
</servlet-mapping>

The above example would map the URL /hello to the servlet com.example.HelloWorld.

You can also do some wildcard mapping. For example:

<servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>*.html</url-pattern>
</servlet-mapping>

This would map requests ending in “.html” to the HelloWorld servlet. But you aren’t limited to any particular extensions. You could use anything you want:

<servlet-mapping>
    <servlet-name>HelloWorld</servlet-name>
    <url-pattern>*.foo</url-pattern>
</servlet-mapping>

All of this configuration takes place in your web application’s web.xml file.