Difference between "dispatcherServlet" and "appServlet" in spring MVC - spring

Question

Difference between "dispatcherServlet" and "appServlet" in spring MVC. Can I get any samples or references?

Answer 1

Technically both are HttpServlet implementation to handle incoming requests. DispatcherServlet is Spring provided servlet implemenation having all essential features like exception handling ..
You have to just write your Request mappers ,it will handle all request.
AppServlet is nothing different, just your implementation for specific handling of requests.
Both will work in same way .If you dont have any specific handling than you can just go with Spring DispatcherServlet.
For example..
<servlet>
<servlet-name>DispatcherServlet</servlet-name>
<servlet-class>
org.springframework.web.servlet.DispatcherServlet
</servlet-class>
<load-on-startup>1</load-on-startup>
<!-- Custom Servlet -->
<servlet>
<servlet-name>CustomServlet</servlet-name>
<servlet-class>org.abc.CustomServlet</servlet-class>
<init-param>
<param-name>debug</param-name>
<param-value>false</param-value>
</init-param>
<init-param>
<param-name>any-other-Parameter</param-name>
<param-value>false</param-value>
</init-param>
<servlet-mapping>
<servlet-name>DispatcherServlet</servlet-name>
<url-pattern>*.do</url-pattern>
<url-pattern>/myapp/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>CustomServlet</servlet-name>
<url-pattern>/myapp2/*</url-pattern>
</servlet-mapping>
For reference of DispatcherServlet you can see http://www.mkyong.com/spring-mvc/spring-mvc-hello-world-example/

Answer 2

to understand this, you can have a look on below configuration :
<servlet>
<servlet-name>appServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/spring/servlet-context.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
In above configuration DispatcherServlet is the servlet class provided by spring framework.
The job of the DispatcherServlet is to take an incoming URI and find the
right combination of handlers (generally methods on Controller classes)
and views (generally JSPs) that combine to form the page or resource
that's supposed to be found at that location.
while appServlet is the custom name given by you in your web.xml file.