Unlock Spring’s Power: Global Exception Handling, Custom Interceptors, and Thread‑Local Scopes

1. Global Exception Handling

When an API throws an exception, the raw stack trace is exposed to the user. Example controller code:

@RequestMapping("/test")
@RestController
public class TestController {
    @GetMapping("/division")
    public String division(@RequestParam("a") int a, @RequestParam("b") int b) {
        return String.valueOf(a / b);
    }
}

Calling 127.0.0.1:8080/test/division?a=10&b=0 returns a detailed error page, which is a poor user experience. Using a global exception handler solves this:

@RestControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(Exception.class)
    public String handleException(Exception e) {
        if (e instanceof ArithmeticException) {
            return "params error";
        }
        return "Internal server exception";
    }
}

Now the user sees a friendly message "params error".