Java using Type Response APIs Problems

Question

What are some issues using Generic Types in API Responses? Does it cause any coding bugs, issues, or compatibility headaches? Ccurrently using Java 8, Spring Boot 3, with React 17. I prefer using stable class types.

Generic type as parameter in Java Method

private static <T> List<T> pushBack(List<T> list, Class<T> typeKey) throws Exception {
    list.add(typeKey.getConstructor().newInstance());
    return list;
}

I see a problem thread here, https://github.com/swagger-api/swagger-core/issues/498

score 1 · Accepted Answer · edited Jun 17 '23 at 06:56

There is no issue in using generics in Java unless it is implemented well. I have seen many projects using response wrappers for API calls in spring boot.

Here is an example where generics are used in response entity.

@Builder
@NoArgsConstructor
@Data
@AllArgsConstructor
public class Response<T extends Object> {
    private LocalDateTime timestamp;
    private int status;
    private Boolean isSuccess;
    private String message;
    private T data;
}

It is a wrapper class where every API response will contain the following fields

public class ResponseWrapper {
    public static <T extends Object> ResponseEntity<T> generateResponse(HttpStatus status, boolean isSuccess, String message, T responseObj) {
        Response<Object> response = Response.builder().timestamp(LocalDateTime.now()).status(status.value()).isSuccess(isSuccess).message(message).data(responseObj).build();
        return new ResponseEntity<T>((T) response, status);
    }
    public static <T extends Object> ResponseEntity<T> ok(T responseObj) {
        return generateResponse(HttpStatus.OK, true, "", responseObj);
    }
    public static ResponseEntity<String> message(String message) {
        return generateResponse(HttpStatus.OK, true, message, "");
    }
    public static ResponseEntity<String> error(String message, HttpStatus status) {
        return generateResponse(status, false, message, "");
    }
}

This is the wrapper that needs to be called from the controller

    @GetMapping(value = "/dummy/users", produces = { Api.V10 })
    public ResponseEntity<List<User>> getAllDummyUsers() {
        return ResponseWrapper.ok(userService.getAllUsers());
    }

Hope I understood the question and was able to provide an answer.

Java using Type Response APIs Problems

1 Answers1