@WebServlet Annotation and servlet-mapping differences

Question

In my servlet class, I have annotated the class with:

@WebServlet("/OnlinePostListener/testFromAnnotation")
public class OnlinePostListener extends HttpServlet {
   ...
}

My web.xml contains the following:

<servlet>
    <description>
    </description>
    <display-name>OnlinePostListener</display-name>
    <servlet-name>OnlinePostListener</servlet-name>
    <servlet-class>com.me.forwardingProxy.OnlinePostListener</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>OnlinePostListener</servlet-name>
    <url-pattern>/testFromWebXML</url-pattern>
</servlet-mapping>

My servlet only responds when I access the URL:

http://localhost:8080/forwardingProxy/OnlinePostListener/testFromAnnotation

but not:

http://localhost:8080/forwardingProxy/OnlinePostListener/testFromWebXML

What is the difference between the @WebServlet's annotation and servlet-mapping? Why is the servlet-mapping not working for this URL-pattern?

KNU KNU · Accepted Answer · 2014-11-05T12:35:56

It's because you are using wrong url to fetch the servlet in the later case.

Use the correct url :

http://localhost:8080/forwardingProxy/testFromWebXML

ERROR : You used an extra /OnlinePostListener in later case.

In the first case your mapped URL for the specified servlet is "/OnlinePostListener/testFromAnnotation" hence you have used this string as appending URL to http://localhost:8080/forwardingProxy BUT in the later case you have mapped the servlet to /testFromWebXML ( AND NOT /OnlinePostListener/testFromWebXML).

If,however, you insist on using the URL http://localhost:8080/forwardingProxy/OnlinePostListener/testFromWebXML to exploit web.xml you should make following changes :

<servlet-mapping>
    <servlet-name>OnlinePostListener</servlet-name>
    <url-pattern>/OnlinePostListener/testFromWebXML</url-pattern>
</servlet-mapping>

@WebServlet Annotation and servlet-mapping differences

2 Answers