Java Spring – how to handle missing required request parameters

If a required @RequestParam is not present in the request, Spring will throw a MissingServletRequestParameterException exception. You can define an @ExceptionHandler in the same controller or in a @ControllerAdvice to handle that exception:

@ExceptionHandler(MissingServletRequestParameterException.class)
public void handleMissingParams(MissingServletRequestParameterException ex) {
    String name = ex.getParameterName();
    System.out.println(name + " parameter is missing");
    // Actual exception handling
}

I want to return let’s say a different page. How to I achieve this?

As the Spring documentation states:

Much like standard controller methods annotated with a @RequestMapping
annotation, the method arguments and return values of
@ExceptionHandler methods can be flexible. For example, the
HttpServletRequest can be accessed in Servlet environments and the
PortletRequest in Portlet environments. The return type can be a
String, which is interpreted as a view name, a ModelAndView object, a
ResponseEntity, or you can also add the @ResponseBody to have the
method return value converted with message converters and written to
the response stream.