Request Mapping

Introduction

Request mapping is Spring's mechanism for mapping HTTP URLs to specific methods. Learn how to define paths, HTTP methods, and parameters so your endpoints are better structured.

@RequestMapping

The base annotation for mapping requests to handler methods. It can be placed at the class level or the method level.

@RestController
@RequestMapping("/api/products")
public class ProductController {

    @RequestMapping(value = "/{id}", method = RequestMethod.GET)
    public Product getById(@PathVariable Long id) {
        return productService.findById(id);
    }
}

@RequestMapping parameters:

Parameter	Description	Example
`value` / `path`	URL path	`"/users"`, `"/{id}"`
`method`	HTTP method	`RequestMethod.GET`
`produces`	Response content type	`"application/json"`
`consumes`	Request content type	`"application/json"`

Shortcut Annotations

Spring provides shortcuts to keep the code concise and readable.

@GetMapping("/all")
public List<Product> getAll() {
    return productService.findAll();
}

@PostMapping("/create")
public Product create(@RequestBody Product product) {
    return productService.save(product);
}

@PutMapping("/{id}")
public Product update(@PathVariable Long id, @RequestBody Product product) {
    return productService.update(id, product);
}

@DeleteMapping("/{id}")
public void delete(@PathVariable Long id) {
    productService.delete(id);
}

@PatchMapping("/{id}")
public Product patch(@PathVariable Long id, @RequestBody Map<String, Object> fields) {
    return productService.partialUpdate(id, fields);
}

Annotation	HTTP Method	Use Case
`@GetMapping`	GET	Fetch data
`@PostMapping`	POST	Create new data
`@PutMapping`	PUT	Update all data
`@PatchMapping`	PATCH	Update part of the data
`@DeleteMapping`	DELETE	Delete data

@PathVariable

Captures values from the URL path. Ideal for identifying a resource.

@GetMapping("/category/{categoryId}/products/{productId}")
public Product getByCategory(
        @PathVariable Long categoryId,
        @PathVariable Long productId) {
    return productService.findByCategoryAndId(categoryId, productId);
}

@GetMapping("/users/{id:\\d+}")
public User getById(@PathVariable Long id) {
    return userService.findById(id);
}

@RequestParam

Captures query parameters from the URL. Example: /products?sort=name&page=0.

@GetMapping("/search")
public List<Product> search(
        @RequestParam String keyword,
        @RequestParam(defaultValue = "0") int page,
        @RequestParam(defaultValue = "10") int size,
        @RequestParam(required = false) String sort) {
    return productService.search(keyword, page, size, sort);
}

Parameter	Default	Purpose
`defaultValue`	-	Value to use if the parameter is missing
`required`	true	Whether it must be provided
`name`	-	Custom parameter name

Combining Path Variables & Query Params

@RestController
@RequestMapping("/api/v1")
public class OrderController {

    @GetMapping("/users/{userId}/orders")
    public Page<Order> getUserOrders(
            @PathVariable Long userId,
            @RequestParam(defaultValue = "0") int page,
            @RequestParam(defaultValue = "5") int size,
            @RequestParam(defaultValue = "createdAt,desc") String[] sort) {
        return orderService.getOrdersByUser(userId, page, size, sort);
    }
}

Path Matching

Spring supports wildcards and patterns in paths:

@GetMapping("/files/**")        // Matches all paths under /files/
@GetMapping("/users/{id:[a-z]+}") // Lowercase letters only
@GetMapping({"/old", "/new"})    // Multiple paths

Summary

Use shortcut annotations (@GetMapping, etc.) for cleaner code.
@PathVariable for capturing parts of the URL.
@RequestParam for query strings.

Next chapter: We'll cover Request & Response Body — how to read input from the client and customize responses.