Request Mapping Example: Reading the Path, the Query String and the Body

A request carries data in three places, and each place has its own annotation.

A request can carry data in three places: in the path (/rides/42), in the query string after the ? (?status=active), and in the body, usually as JSON. A controller method, a method on the class that answers web requests, reads each with its own annotation: @PathVariable, @RequestParam and @RequestBody.

The controller below uses all three. @RequestMapping("/rides") on the class puts /rides in front of every method's path:

java

@RestController
@RequestMapping("/rides")
class RideController {

    @GetMapping("/{id}")
    ResponseEntity<Ride> getRide(@PathVariable String id) { /* ... */ }

    @GetMapping
    ResponseEntity<?> list(@RequestParam(defaultValue = "all") String status) { /* ... */ }

    @PostMapping
    ResponseEntity<Ride> createRide(@RequestBody Ride ride) { /* ... */ }
}

Where each annotation reads from
Annotation	Reads from	Example
`@PathVariable`	A segment of the URL itself	`/rides/42` gives `id = "42"`
`@RequestParam`	The query string	`/rides?status=active` gives `status = "active"`
`@RequestBody`	The request body, converted from JSON by Jackson, Boot's JSON library,	A JSON object becomes a `Ride`

@RequestParam(defaultValue = "all") makes the parameter optional, so /rides with no query string gets status = "all". Without a default, a request that leaves the parameter out is rejected with 400 Bad Request.

So each piece of request data has one obvious home: the identity of a resource in the path, filters and options in the query string, and the thing being created or changed in the body.

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