When use ResponseEntity<T> and #RestController for Spring RESTful applications - spring

Question

I am working with Spring Framework 4.0.7, together with MVC and Rest
I can work in peace with:
#Controller
ResponseEntity<T>
For example:
#Controller
#RequestMapping("/person")
#Profile("responseentity")
public class PersonRestResponseEntityController {
With the method (just to create)
#RequestMapping(value="/", method=RequestMethod.POST)
public ResponseEntity<Void> createPerson(#RequestBody Person person, UriComponentsBuilder ucb){
logger.info("PersonRestResponseEntityController - createPerson");
if(person==null)
logger.error("person is null!!!");
else
logger.info("{}", person.toString());
personMapRepository.savePerson(person);
HttpHeaders headers = new HttpHeaders();
headers.add("1", "uno");
//http://localhost:8080/spring-utility/person/1
headers.setLocation(ucb.path("/person/{id}").buildAndExpand(person.getId()).toUri());
return new ResponseEntity<>(headers, HttpStatus.CREATED);
}
to return something
#RequestMapping(value="/{id}", method=RequestMethod.GET)
public ResponseEntity<Person> getPerson(#PathVariable Integer id){
logger.info("PersonRestResponseEntityController - getPerson - id: {}", id);
Person person = personMapRepository.findPerson(id);
return new ResponseEntity<>(person, HttpStatus.FOUND);
}
Works fine
I can do the same with:
#RestController (I know it is the same than #Controller + #ResponseBody)
#ResponseStatus
For example:
#RestController
#RequestMapping("/person")
#Profile("restcontroller")
public class PersonRestController {
With the method (just to create)
#RequestMapping(value="/", method=RequestMethod.POST)
#ResponseStatus(HttpStatus.CREATED)
public void createPerson(#RequestBody Person person, HttpServletRequest request, HttpServletResponse response){
logger.info("PersonRestController - createPerson");
if(person==null)
logger.error("person is null!!!");
else
logger.info("{}", person.toString());
personMapRepository.savePerson(person);
response.setHeader("1", "uno");
//http://localhost:8080/spring-utility/person/1
response.setHeader("Location", request.getRequestURL().append(person.getId()).toString());
}
to return something
#RequestMapping(value="/{id}", method=RequestMethod.GET)
#ResponseStatus(HttpStatus.FOUND)
public Person getPerson(#PathVariable Integer id){
logger.info("PersonRestController - getPerson - id: {}", id);
Person person = personMapRepository.findPerson(id);
return person;
}
My questions are:
when for a solid reason or specific scenario one option must be used mandatorily over the other
If (1) does not matter, what approach is suggested and why.

Answer 1

ResponseEntity is meant to represent the entire HTTP response. You can control anything that goes into it: status code, headers, and body.
#ResponseBody is a marker for the HTTP response body and #ResponseStatus declares the status code of the HTTP response.
#ResponseStatus isn't very flexible. It marks the entire method so you have to be sure that your handler method will always behave the same way. And you still can't set the headers. You'd need the HttpServletResponse.
Basically, ResponseEntity lets you do more.

Answer 2

To complete the answer from Sotorios Delimanolis.
It's true that ResponseEntity gives you more flexibility but in most cases you won't need it and you'll end up with these ResponseEntity everywhere in your controller thus making it difficult to read and understand.
If you want to handle special cases like errors (Not Found, Conflict, etc.), you can add a HandlerExceptionResolver to your Spring configuration. So in your code, you just throw a specific exception (NotFoundException for instance) and decide what to do in your Handler (setting the HTTP status to 404), making the Controller code more clear.

Answer 3

According to official documentation: Creating REST Controllers with the #RestController annotation
#RestController is a stereotype annotation that combines #ResponseBody
and #Controller. More than that, it gives more meaning to your
Controller and also may carry additional semantics in future releases
of the framework.
It seems that it's best to use #RestController for clarity, but you can also combine it with ResponseEntity for flexibility when needed (According to official tutorial and the code here and my question to confirm that).
For example:
#RestController
public class MyController {
#GetMapping(path = "/test")
#ResponseStatus(HttpStatus.OK)
public User test() {
User user = new User();
user.setName("Name 1");
return user;
}
}
is the same as:
#RestController
public class MyController {
#GetMapping(path = "/test")
public ResponseEntity<User> test() {
User user = new User();
user.setName("Name 1");
HttpHeaders responseHeaders = new HttpHeaders();
// ...
return new ResponseEntity<>(user, responseHeaders, HttpStatus.OK);
}
}
This way, you can define ResponseEntity only when needed.
Update
You can use this:
return ResponseEntity.ok().headers(responseHeaders).body(user);

Answer 4

A proper REST API should have below components in response
Status Code
Response Body
Location to the resource which was altered(for example, if a resource was created, client would be interested to know the url of that location)
The main purpose of ResponseEntity was to provide the option 3, rest options could be achieved without ResponseEntity.
So if you want to provide the location of resource then using ResponseEntity would be better else it can be avoided.
Consider an example where a API is modified to provide all the options mentioned
// Step 1 - Without any options provided
#RequestMapping(value="/{id}", method=RequestMethod.GET)
public #ResponseBody Spittle spittleById(#PathVariable long id) {
return spittleRepository.findOne(id);
}
// Step 2- We need to handle exception scenarios, as step 1 only caters happy path.
#ExceptionHandler(SpittleNotFoundException.class)
#ResponseStatus(HttpStatus.NOT_FOUND)
public Error spittleNotFound(SpittleNotFoundException e) {
long spittleId = e.getSpittleId();
return new Error(4, "Spittle [" + spittleId + "] not found");
}
// Step 3 - Now we will alter the service method, **if you want to provide location**
#RequestMapping(
method=RequestMethod.POST
consumes="application/json")
public ResponseEntity<Spittle> saveSpittle(
#RequestBody Spittle spittle,
UriComponentsBuilder ucb) {
Spittle spittle = spittleRepository.save(spittle);
HttpHeaders headers = new HttpHeaders();
URI locationUri =
ucb.path("/spittles/")
.path(String.valueOf(spittle.getId()))
.build()
.toUri();
headers.setLocation(locationUri);
ResponseEntity<Spittle> responseEntity =
new ResponseEntity<Spittle>(
spittle, headers, HttpStatus.CREATED)
return responseEntity;
}
// Step4 - If you are not interested to provide the url location, you can omit ResponseEntity and go with
#RequestMapping(
method=RequestMethod.POST
consumes="application/json")
#ResponseStatus(HttpStatus.CREATED)
public Spittle saveSpittle(#RequestBody Spittle spittle) {
return spittleRepository.save(spittle);
}