Snippet

Handling Specific Controller Exceptions with ExceptionHandler

The @ExceptionHandler annotation in Spring catches and handles specific exceptions thrown by controller methods, converting errors into clean HTTP responses.

snippet.java

java

@RestController
@RequestMapping("/users")
public class UserController {
 
    @GetMapping("/{id}")
    public String getUser(@PathVariable Long id) {
        if (id < 1) {
            throw new IllegalArgumentException("User ID must be positive.");
        }
        return "User: " + id;
    }
 
    @ExceptionHandler(IllegalArgumentException.class)
    public ResponseEntity<String> handleInvalidId(IllegalArgumentException ex) {
        return ResponseEntity.badRequest().body(ex.getMessage());
    }
}

spring

Breakdown

if (id < 1) { throw new IllegalArgumentException(...); }

Checks validation logic and triggers an IllegalArgumentException if the ID is invalid.

@ExceptionHandler(IllegalArgumentException.class)

Specifies that this handler method intercepts any IllegalArgumentException within this controller.

return ResponseEntity.badRequest().body(ex.getMessage());

Constructs and returns an HTTP 400 (Bad Request) response containing the exception message.

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Handling Specific Controller Exceptions with ExceptionHandler

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