What Is The Purpose Of Dispatcherservlet Inward Saltation Mvc Framework?

If you lot convey worked alongside Spring MVC hence you lot should know what is a DispatcherServlet? It's genuinely the see of Spring MVC, exactly 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 betoken of entry inwards your application. It handles all incoming requests. It is besides the distich betwixt Java in addition to Spring. Btw, the DispatcherServlet is similar whatever other Servlet is declared inwards the web.xml alongside a URL pattern just the exclusively exceptional affair 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 chore 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 besides 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 two is available inwards Classpath) to convert the response returned past times convert into a JSON string.

You tin farther see Spring Framework 5: Beginner to Guru to larn to a greater extent than close developing RESTful spider web services using Spring iv in addition to Spring 5.

How does DispatcherServlet procedure asking inwards Spring MVC

As I said before, Dispatcher Servlet is used to handgrip all incoming requests in addition to road them through unlike Spring Controllers for farther processing. To accomplish this, it determines which controllers should handgrip 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 in addition to DefaultAnnotationHandlerMapping, which is driven by @RequestMapping annotation.

In guild to discovery the right methods for treatment the request, it scans through all the classes declared using @Controller tone in addition to it besides uses @RequestMapping tone to discovery the types in addition to methods responsible for treatment requests. @RequestMapping tone tin 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") in addition to past times presence of HTTP asking header like
@RequestMapping("path", header="content-type=text/*").

You tin besides apply @RequestMapping tone at the course of written report score to filter incoming requests. If you lot are interested, you lot tin farther check Spring Framework 5: Beginner to Guru course on Udemy to larn the amount attain of options you lot tin utilization alongside the @RequestMapping annotation. I'll besides write an article close that just till hence this course of written report is i of the best resources.

Anyway, afterwards processing the asking Controller returns logical thought holler in addition to model to DispatcherServlet. It hence consults to thought resolvers to discovery the actual View to homecoming the output.

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

After this DispatcherServlet contacts the chosen thought e.g. a JSP file alongside model information in addition to 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 withdraw a thought e.g. inwards instance of RESTful Web services.

Their handler method lead writes into response using @ResponseBody tone in addition to DispatcherServlet lead homecoming a response to the client. See REST alongside Spring course to larn to a greater extent than close developing in addition to testing RESTful Web service using Spring MVC.

10 Points close DispatcherServlet

In this article, I am going to part approximately of the useful in addition to essential things close DispatcherServlet a Java Web Developer should know. These points volition non exclusively assist you lot to sympathise the chore of DispatcherServlet inwards Spring MVC amend just besides encourage you lot to larn to a greater extent than close them past times exploring in addition to researching each point.


1) The DispatcherServlet is the principal 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 plant internally for to a greater extent than details of the inner workings of Spring.


6) Spring's DispatcherServlet is besides completely integrated alongside the Spring IoC container in addition to 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 way 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 commencement asking because DispatcherServlet does a lot of chore at the startup to scan in addition to discovery all controllers in addition to 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 live overridden inwards the servlet-specific scope, in addition to novel scope-specific beans tin live defined locally to a given servlet instance.


10) The DispatcherServlet of Spring MVC framework tin besides homecoming the last-modification-date, every bit specified past times the Servlet API. It determines the concluding alteration appointment past times looking for an appropriate handler mapping in addition to essay out if the handler that is constitute implements the LastModified interface. If yes, hence it calls the getLastModified(request) method of the LastModified interface in addition to value is returned to the client.


That's all close DispatcherServlet of Spring MVC framework. As I said, the DispatcherServlet is the backbone of Spring MVC in addition to serves every bit the principal controller which routes unlike HTTP asking to corresponding Spring Controllers. It is an implementation of Front Controller blueprint pattern in addition to provides a unmarried entry betoken to your Spring spider web application.

You configure DispatcherServlet inwards the web.xml just gives it load-on-startup value 1 to propose container to charge this Servlet during startup in addition to non when a asking comes up. This reduces response fourth dimension for the commencement 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 in addition to @Controller inwards Spring MVC? (answer)
• 23 Spring MVC Interview questions for two to three 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 assist inwards Job in addition to Career? (article)
• Top v Spring Certification Mock Exams (list)
• Spring Framework MasterClass past times Udemy (see)
• Difference betwixt @Autowired in addition to @Injection annotations inwards Spring? (answer)
• 5 Spring in addition to Hibernate online courses for Java developers (list)

Thanks for reading this article hence far. If you lot similar this article hence delight part alongside your friends in addition to colleagues. If you lot convey whatever question, suggestion, or feedback or you lot convey whatever betoken close dispatcher servlet which is non mentioned hither just worth knowing hence delight driblet a comment in addition to I'll include it inwards the principal article.

P. S. - If you lot don't hear learning from gratis resources hence you lot tin besides cheque out my listing of  Free Spring Core in addition to Spring Boot courses for Java developers to start your journey.

Sumber https://javarevisited.blogspot.com/