Java ResponseEntity

Java ResponseEntity is a class used to represent HTTP response entities. It allows programmers to build responses that include both a response body and HTTP headers, as well as the HTTP status code.

Usage

To use the ResponseEntity class, start by creating an instance of the class and specifying the expected response type. Here's an example that returns a plain text response:

@GetMapping(value = "/api/hello")
public ResponseEntity<String> sayHello() {
    return new ResponseEntity<>("Hello World!", HttpStatus.OK);
}

To return a JSON response, use the ResponseEntity class along with the @ResponseBody annotation:

@GetMapping(value = "/api/person/{id}")
@ResponseBody
public ResponseEntity<Person> getPersonById(@PathVariable Long id) {
    Person person = personService.getPersonById(id);
    if (person == null) {
        return new ResponseEntity<>(HttpStatus.NOT_FOUND);
    }
    return new ResponseEntity<>(person, HttpStatus.OK);
}

HTTP Headers

To add additional HTTP headers to the response, add them to an instance of the HttpHeaders class and pass the headers to the ResponseEntity constructor:

@GetMapping(value = "/api/person/{id}")
@ResponseBody
public ResponseEntity<Person> getPersonById(@PathVariable Long id) {
    HttpHeaders headers = new HttpHeaders();
    headers.setCacheControl(CacheControl.noCache());
    Person person = personService.getPersonById(id);
    if (person == null) {
        return new ResponseEntity<>(HttpStatus.NOT_FOUND);
    }
    return new ResponseEntity<>(person, headers, HttpStatus.OK);
}

Conclusion

ResponseEntity is a powerful tool for building custom HTTP responses in Java, allowing programmers to easily specify the response body, HTTP headers, and status code. Its flexibility makes it a useful tool for any Java-based web application.