How does handler mapping work in Spring MVC?

Handler mapping in Spring MVC maps request URIs to handler methods. The process includes: receiving the request URI, parsing the request URI, and creating a HandlerExecutionChain object containing the handler method and request-response information. Its main components are: mapping registry, request matcher, handler adapter. A practical example showing how to use the RequestMapping annotation and handler mapping to map the request URI "/hello" to the hello() method.

Into Spring MVC handler mapping

Introduction

Spring MVC The handler map is an important component that is responsible for mapping requests to handler methods. This article will delve into how handler mapping works and demonstrate its use through a practical case.

The internal mechanism of handler mapping

Handler mapping is a key part of the request processing chain. Its responsibilities include:

• Receive the request URI
• Parse the request URI to determine the handler method
• Create a HandlerExecutionChain object that contains information about the handler method and request-response details

To To implement these functions, the handler mapping contains the following main components:

• Mapping registry: It stores the mapping relationship between the request URI and the handler method.
• Request matcher: It uses the request URI to find a mapping entry that matches it.
• Handler Adapter: It wraps handler methods into HandlerExecutionChain objects so that the Spring MVC framework can call them.

Practical case

To demonstrate handler mapping, we create a simple Spring MVC controller:

@Controller
public class MyController {

    @RequestMapping("/hello")
    public String hello() {
        return "hello";
    }
}

In In the RequestMapping annotation, we specify that the request URI "/hello" is mapped to the hello() method.

In the Spring MVC configuration, we need to configure the handler mapping:

<mvc:annotation-driven/>

This configuration enables Spring MVC's annotation-driven support, which includes handler mapping.

When a request arrives at the URI "/hello", the handler mapping does the following:

1. Parses the request URI and finds the matching mapping entry, which is "/hello".
2. Use a request matcher to determine the handler method, which is hello().
3. Create a HandlerExecutionChain object containing the hello() method and request-response details.

Spring MVC will then call the hello() method and return the "hello" view.

Conclusion

Handler mapping in Spring MVC is a complex but powerful component that is responsible for mapping requests to handler methods. By understanding its internals and how to use it, you can create scalable and robust web applications.

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