[FIXED] return different type of response from controller when there is an error state

Issue

How do I handle error states inside a controller?

For example: My controller which accepts two headers. If both the headers are null then it's a problem so return response of type ErrorResponse else if all ok then return response of type customer.

However, there is a problem as we defined the handler method to return ResponseEntity<Customer>.

My controller:

@PostMapping("/generate/send")
fun handleRequest( @RequestHeader header1: String,
                    @RequestHeader header2: String): ResponseEntity<Customer> {
     
    if(header1 == null && header2== null) { // ERROR if both header null
      
        return ResponseEntity(ErrorResponse(""), HttpStatus.BAD_REQUEST )
    }

    return ResponseEntity(Customer(), HttpStatus.OK )
}

how do refactor my code to prevent this or handle this type of situation where I have to return a different type because of an error?

Solution

You can use ResponseEntity<?> to return either Customer or ErrorResponse like this.

@PostMapping("/generate/send")
fun handleRequest( @RequestHeader header1: String,
                    @RequestHeader header2: String): ResponseEntity<?> {
       // ...
}

Answered By - J.F.
Answer Checked By - Marie Seifert (JavaFixing Admin)