What Is The Role Of Dispatcherservlet Inwards Leap Mvc Framework?

If you lot bring worked alongside Spring MVC hence you lot should know what is a DispatcherServlet? It's genuinely the pump of Spring MVC, just the C of MVC blueprint pattern or Controller. Every unmarried spider web asking which is supposed to live processed past times Spring MVC goes through DispatcherServlet. In general, its an implementation of Front Controller Pattern which provides a unmarried bespeak of entry inwards your application. It handles all incoming requests. It is every bit good the duo betwixt Java as well as Spring. Btw, the DispatcherServlet is similar whatever other Servlet is declared inwards the web.xml alongside a URL pattern only the solely especial matter is that the URL pattern for dispatcher servlet is plenty to map every unmarried spider web asking to DispathcherServlert.

It is responsible for asking treatment past times delegating requests to additional components of Spring MVC e.g. actual controller classes i.e. those which are annotated using @Controller or @RestController (in instance of RESTful Web Services), Views, View Resolvers, handler mappers etc.

Though the project of actual asking mapping is done past times @RequestMapping annotation, it's genuinely the DispatcherServlet which delegates asking to the corresponding controller.

In the instance of RESTful spider web services, it is every bit good responsible for finding the right message converter to convert the response into the format customer is expecting e.g. JSON, XML, or TEXT.

For example, if a customer is expecting JSON hence it volition utilization the MappingJacksonHttpMessageConverter or MappingJackson2HttpMessageConverter (depending upon whether Jackson 1 or Jackson ii is available inwards Classpath) to convert the response returned past times convert into a JSON string.

You tin sack farther see Spring Framework 5: Beginner to Guru to larn to a greater extent than almost developing RESTful spider web services using Spring iv as well as Spring 5.

How does DispatcherServlet procedure asking inwards Spring MVC

As I said before, Dispatcher Servlet is used to grip all incoming requests as well as road them through dissimilar Spring Controllers for farther processing. To accomplish this, it determines which controllers should grip the incoming request.

The DispatcherServlet uses HandlerMapping implementations - pre-built or provided every bit business office of the application to road incoming requests to handler objects. By default, it uses BeanNameUrlHandlerMapping as well as DefaultAnnotationHandlerMapping, which is driven by @RequestMapping annotation.

In social club to notice the right methods for treatment the request, it scans through all the classes declared using @Controller musical note as well as it every bit good uses @RequestMapping musical note to notice the types as well as methods responsible for treatment requests. @RequestMapping musical note tin sack map the asking past times path e.g. @RequestMapping(“path”), by HTTP method e.g. @RequestMapping("path", method=RequestMethod.GET), past times asking parameters e.g. @RequestMapping("path"”, method=RequestMethod.POST, params="param1") as well as past times presence of HTTP asking header like
@RequestMapping("path", header="content-type=text/*").

You tin sack every bit good apply @RequestMapping musical note at the cast degree to filter incoming requests. If you lot are interested, you lot tin sack farther check Spring Framework 5: Beginner to Guru course on Udemy to larn the amount attain of options you lot tin sack utilization alongside the @RequestMapping annotation. I'll every bit good write an article almost that only till hence this course of teaching is i of the best resources.

Anyway, afterward processing the asking Controller returns logical persuasion squall as well as model to DispatcherServlet. It hence consults to persuasion resolvers to notice the actual View to homecoming the output.

The persuasion resolution strategy tin sack live specified using a ViewResolver implementation, past times default, DispatcherServlet uses InternalResourceViewResolver to convert logical persuasion squall to actual View object e.g. a JSP.

After this DispatcherServlet contacts the chosen persuasion e.g. a JSP file alongside model information as well as it renders the output depending on the model data. This rendered output is returned to the customer every bit a response. Sometimes you lot don't fifty-fifty demand a persuasion e.g. inwards instance of RESTful Web services.

Their handler method straight writes into response using @ResponseBody musical note as well as DispatcherServlet straight homecoming a response to the client. See REST alongside Spring course to larn to a greater extent than almost developing as well as testing RESTful Web service using Spring MVC.

10 Points almost DispatcherServlet

In this article, I am going to percentage around of the useful as well as essential things almost DispatcherServlet a Java Web Developer should know. These points volition non solely aid you lot to empathise the project of DispatcherServlet inwards Spring MVC improve only every bit good encourage you lot to larn to a greater extent than almost them past times exploring as well as researching each point.


1) The DispatcherServlet is the chief controller of Spring MVC Application. All incoming spider web asking passes through DispatcherServlet earlier processed past times private Spring controllers i.e classes annotated using @Controller annotation.

2) The DispatcherServlet of Spring MVC is an Implementation of Front Controller Pattern (see  how Spring MVC works internally for to a greater extent than details of the inner workings of Spring.


6) Spring's DispatcherServlet is every bit good completely integrated alongside the Spring IoC container as well as every bit such allows you lot to utilization every characteristic of Spring framework e.g. dependency injection.


7) The dispatcher servlet is configured every bit load-on-startup = 1 which agency this Servlet should live created past times Servlet container when you lot deploy the application rather than creating when a asking arrived for this request.

This is done to cut back the response fourth dimension of the kickoff asking because DispatcherServlet does a lot of project at the startup to scan as well as notice all controllers as well as asking mappings. See 

9) In the Spring MVC framework, each DispatcherServlet has its ain WebApplicationContext (see Spring inwards Action), which inherits all the beans already defined inwards the root WebApplicationContext. These inherited beans tin sack live overridden inwards the servlet-specific scope, as well as novel scope-specific beans tin sack live defined locally to a given servlet instance.


10) The DispatcherServlet of Spring MVC framework tin sack every bit good homecoming the last-modification-date, every bit specified past times the Servlet API. It determines the final alteration engagement past times looking for an appropriate handler mapping as well as attempt if the handler that is industrial plant life implements the LastModified interface. If yes, hence it calls the getLastModified(request) method of the LastModified interface as well as value is returned to the client.


That's all almost DispatcherServlet of Spring MVC framework. As I said, the DispatcherServlet is the backbone of Spring MVC as well as serves every bit the chief controller which routes dissimilar HTTP asking to corresponding Spring Controllers. It is an implementation of Front Controller blueprint pattern as well as provides a unmarried entry bespeak to your Spring spider web application.

You configure DispatcherServlet inwards the web.xml only gives it load-on-startup value 1 to propose container to charge this Servlet during startup as well as non when a asking comes up. This reduces response fourth dimension for the kickoff request.

Further Learning
Spring Master Class - Beginner to Expert
Spring Framework 5: Beginner to Guru
REST alongside Spring past times Baeldung


Other Spring related articles you lot may similar to explore

• Difference between @RestControler as well as @Controller inwards Spring MVC? (answer)
• 23 Spring MVC Interview questions for ii to iii years experienced (list)
• What is the utilization of DispatcherServlet inwards Spring MVC? (answer)
• How to enable Spring safety inwards Java application? (answer)
• Does Spring certification aid inwards Job as well as Career? (article)
• Top five Spring Certification Mock Exams (list)
• Spring Framework MasterClass past times Udemy (see)
• Difference betwixt @Autowired as well as @Injection annotations inwards Spring? (answer)
• 5 Spring as well as Hibernate online courses for Java developers (list)

Thanks for reading this article hence far. If you lot similar this article hence delight percentage alongside your friends as well as colleagues. If you lot bring whatever question, suggestion, or feedback or you lot bring whatever bespeak almost dispatcher servlet which is non mentioned hither only worth knowing hence delight driblet a comment as well as I'll include it inwards the chief article.

P. S. - If you lot don't heed learning from costless resources hence you lot tin sack every bit good depository fiscal establishment check out my listing of  Free Spring Core as well as Spring Boot courses for Java developers to start your journey.