ResponseEntity

ResponseEntity<?>

• When responding to something over http protocol, look to respond with a ResponseEntity<> object, which wraps around some other data type. It is a class that represents the HTTP response returned by a controller method. It encapsulates the response status, headers, and body, allowing you to customize and control the HTTP response returned to the client.
  • Here are popular use cases:

@GetMapping("/data")
public ResponseEntity<String> getData() {
    String data = "This is the response data.";
    return ResponseEntity.ok(data); // 200
}

// In another method or class
ResponseEntity<String> responseEntity = getData();
String responseData = responseEntity.getBody(); // can use hasBody() to check first too

In short, it wraps whatever data we want to return in a ResponseEntity object, which can then pass additional parameter such as HTTP.STATUS_CODE and header data.

In addition, we can use these with wildcards. The <?> part is a wildcard, which means that we can expect any type. This means we can return any type within the ResponseEntity, and it will be fine.