Best practice to send response in spring boot

Question

I'm coding REST Api-s in spring boot. I want to make sure that my code is readable to front-end developers using swagger API development tool (Swagger). For example

@GetMapping("/getOne")
    public ResponseEntity<?> getOne(@RequestParam String id) {
        try {
            return new ResponseEntity<Branch>(branchService.getOne(id), HttpStatus.OK);
        } catch (Exception e) {
            return new ResponseEntity<FindError>(new FindError(e.getMessage()), HttpStatus.BAD_REQUEST);
        }
    }

If the request is successful, response is a Branch object, if fails, the response is a FindError object which has only one attribute (message). So both can be carried out depends on the response. But the swagger UI doesn't show how the response should be shown, because I use "?" as generic type. Is this a best practice to catch an error? (This coding documentation swagger is not useful to front-end developers since it doesn't show the response object). Or any best practice for the above problem?

There are a lot of method which return different object like Branch. Thanks in advance

Answer 1

First of all you should follow the best practices of a RESTful API . Don't use verbs, instead use nouns as URL.So instead of @GetMapping("/getOne") , you can write it as @GetMapping("/branch/{id}") . You can refer this blog https://blog.mwaysolutions.com/2014/06/05/10-best-practices-for-better-restful-api/

@2ndly , Don't return a generic type as ? , instead you can user the specific type , here as Branch and do central exception handling . The following code snippet can help you :

@GetMapping("/branch/{id}")
public ResponseEntity<Branch> getBranch(@Pathvariable String id) {
{
    Branch branch = branchService.getOne(id);

    if(branch == null) {
         throw new RecordNotFoundException("Invalid Branch id : " + id);
    }
    return new ResponseEntity<Branch>(branch, HttpStatus.OK);
}

RecordNotFoundException.java

@ResponseStatus(HttpStatus.NOT_FOUND)
public class RecordNotFoundException extends RuntimeException
{
    public RecordNotFoundException(String exception) {
        super(exception);
    }
}

CustomExceptionHandler.java

@ControllerAdvice
public class CustomExceptionHandler extends ResponseEntityExceptionHandler
{
    @ExceptionHandler(Exception.class)
    public final ResponseEntity<Object> handleAllExceptions(Exception ex, WebRequest request) {
        List<String> details = new ArrayList<>();
        details.add(ex.getLocalizedMessage());
        ErrorResponse error = new ErrorResponse("Server Error", details);
        return new ResponseEntity(error, HttpStatus.INTERNAL_SERVER_ERROR);
    }

    @ExceptionHandler(RecordNotFoundException.class)
    public final ResponseEntity<Object> handleRecordNotFoundException(RecordNotFoundException ex, WebRequest request) {
        List<String> details = new ArrayList<>();
        details.add(ex.getLocalizedMessage());
        ErrorResponse error = new ErrorResponse("Record Not Found", details);
        return new ResponseEntity(error, HttpStatus.NOT_FOUND);
    }
}

ErrorResponse.java

public class ErrorResponse
{
    public ErrorResponse(String message, List<String> details) {
        super();
        this.message = message;
        this.details = details;
    }

    private String message;

    private List<String> details;

    //Getter and setters
}

The above class handles multiple exceptions including RecordNotFoundException and you can also customize for payload validations too.

Test Cases :

1) HTTP GET /branch/1 [VALID]

HTTP Status : 200

{
    "id": 1,
    "name": "Branch 1",
    ...
}
2) HTTP GET /branch/23 [INVALID]

HTTP Status : 404

{
    "message": "Record Not Found",
    "details": [
        "Invalid Branch id : 23"
    ]
}