What is @RequestMapping

ghz 9months ago ⋅ 71 views

@RequestMapping is a versatile annotation used in Spring MVC to map HTTP requests to handler methods in controller classes. It allows developers to define URL patterns and associate them with specific controller methods, specifying how incoming requests should be handled.

Here are the key features and uses of @RequestMapping:

  1. Mapping URLs:
    • @RequestMapping is used to map HTTP requests to specific URLs or URL patterns.
    • It can be applied at the class level to define a base URL for all handler methods within the controller, as well as at the method level to define more specific mappings.
  2. HTTP Methods:
    • @RequestMapping supports mapping requests to specific HTTP methods (e.g., GET, POST, PUT, DELETE) using the method attribute.
    • If no specific HTTP method is specified, the mapping applies to all HTTP methods by default.
  3. Path Variables:
    • @RequestMapping supports path variables, which allow dynamic parts of the URL to be extracted and passed as method parameters.
    • Path variables are defined within curly braces {} in the URL pattern and are mapped to method parameters using @PathVariable annotation.
  4. Request Parameters:
    • @RequestMapping can map requests based on request parameters using the params attribute.
    • Request parameters can be specified as key-value pairs (e.g., "paramName=value") or as boolean expressions (e.g., "paramName") to check for the presence or absence of a parameter.
  5. Headers and Consumes/Produces:
    • @RequestMapping supports mapping requests based on request headers using the headers attribute.
    • It also supports mapping requests based on the content type of the request (consumes) and the content type of the response (produces).
  6. Content Negotiation:
    • @RequestMapping supports content negotiation, allowing the same URL to handle requests with different content types (e.g., JSON, XML).
    • Content negotiation is based on the produces attribute, which specifies the supported media types for the response.
  7. Fallback and Default Mapping:
    • @RequestMapping can be used as a fallback mapping for requests that do not match any specific mappings.
    • It can also be used to define default mappings for controller methods that handle requests for the root URL or when no specific path is provided.

Example usage of @RequestMapping:

@Controller
@RequestMapping("/products")
public class ProductController {

    @GetMapping("/{id}")
    public ResponseEntity<Product> getProductById(@PathVariable Long id) {
        // Method logic to retrieve product by ID
    }

    @PostMapping
    public ResponseEntity<Product> createProduct(@RequestBody Product product) {
        // Method logic to create a new product
    }
}

In this example, @RequestMapping is used at the class level to specify the base URL /products for all handler methods within the ProductController class. The @GetMapping and @PostMapping annotations are used at the method level to further define specific URL mappings for handling GET and POST requests, respectively.

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