38-Creating a Complete REST Application

Question 1

What does REST stand for?

Answer 1

REpresentational State Transfer

Question 2

What does REST emphasize?

Answer 2

Scalability

Question 3

What does HATEOAS stand for?

Answer 3

Hypermedia As The Engine of Application State

Question 4

What is the REST specification in Java?

Answer 4

JAX-RS

Question 5

Implementations of JAX-RS

Answer 5

1. Jersey (RI)
2. RESTEasy
3. Restlet
4. CXF

Question 6

What JAX-RS implementations are supported by Spring?

Answer 6

1. Jersey (RI)
2. RESTEasy
3. Restlet
4. CXF

Question 7

Does Spring MVC implement JAX-RS?

Answer 7

No

Question 8

What combined request mapping annotations are supported?

Answer 8

1. GetMapping
2. PostMapping
3. PutMapping
4. PatchMapping
5. DeleteMapping

Question 9

What request methods must use @RequestMapping?

Answer 9

1. HEAD
2. OPTIONS
3. TRACE

Question 10

How to use @RequestMapping?

Answer 10

e.g. @RequestMapping(path=”hello”, method=RequestMethod.GET)

Question 11

What request mappings are implemented automatically by Spring?

Answer 11

1. HEAD

2. OPTIONS

Question 12

What objects help to translate JSON to Java objects and vice versa?

Answer 12

Message converters

Question 13

Which controller method do we need to return a ResponseEntity?

Answer 13

For POST as we need to return the location of the created object
e.g. return ResponseEntity.created(location).build()

Question 14

What response should PUT return?

Answer 14

204 no content and empty body

Question 15

What response should DELETE return?

Answer 15

204 no content and empty body

Question 16

What response should POST return?

Answer 16

201 created with “Location” in the response header

Question 17

HTTP status code of Unsupported Media Type

Answer 17

415 - might be due to the request’s indicated Content-Type or Content-Encoding

Question 18

HTTP status code of cannot generate response body in the requested format

Answer 18

406 Not Acceptable

Due to Accept, Accept-Encoding or Accept-Language

Question 19

HTTP status code of method not supported

Answer 19

405

Question 20

By default, what is the result of controller methods?

Answer 20

view name

Question 21

How to override HTTP status of void method?

Answer 21

@ResponseStatus(HttpStatus.OK) void controllerMethod() {}

Question 22

How to build the location for POST requests?

Answer 22

Using ServletUriComponentsBuilder
e.g. 
URI location = ServletUriComponentsBuilder
				.fromCurrentRequestUri()
				.path("/{resourceId}")
				.buildAndExpand(resourceId)
				.toUri();
return ResponseEntity.created(location).build();

Question 23

What is the return type of a POST controller method?

Answer 23

ResponseEntity

Question 24

UriComponentsBuilder vs. ServletUriComponentsBuilder

Answer 24

UriComponentsBuilder must hard-code URL

ServletUriComponentsBuilder extends UriComponentsBuilder but allows building from relative API path

Question 25

What is the difference between RestTemplate.xxxForObject and RestTemplate.xxxForEntity?

Answer 25

1. xxxForObject(String, Class, Object… urlVariables): T
   return response object if any or null if not found
2. xxxForEntity(String, Class, Object… urlVariables): ResponseEntity

Question 26

How to create a custom RestTemplate?

Answer 26

Inject RestTemplateBuilder and call .build()

Question 27

Example of urlVariables in RestTemplate.xxxForObject

Answer 27

String uri = “/accounts/{id}”;

User user = restTemplate.xxxForObject(uri, User.class, “1”);

Question 28

How to setup your custom API request?

Answer 28

Using RequestEntity
e.g.
request = RequestEntity.post(uri)
.getHeaders().add(HttpHeaders.Authorization, auth)
.contentType(MediaType.APPLICATION_JSON)
.body(newItem);
ResponseEntity response = restTemplate.exchange(request, Void.class);

Question 29

What is WebClient?

Answer 29

1. New client, Support streaming

2. Will Replace RestTemplate

Question 30

How to customize response status for an exception?

Answer 30

e.g. @ResponseStatus(HttpStatus.NOT_FOUND)
class OrderNotFound extends RuntimeException {}
from now, when this exception thrown, client will receive 404 instead of 500

Question 31

How to customize response status for existing exceptions (i.e. exceptions from third-party libs)?

Answer 31

Create method inside the controller e.g.
@ResponseStatus(HttpStatus.CONFLICT) // 409
@ExceptionHandler({DataIntegrityViolationException.class})
public void conflict() {
// could add the exception, response, etc. as method params
}

Question 32

Example of calling a GET API to get a user by id using WebClient

Answer 32

e.g.
client = WebClient.create();
Mono result = client.get()
    .uri("/users/{id}", 1)
    .accept(MediaType.APPLICATION_JSON)
    .retrieve()
    .bodyToMono(User.class);
return result.block();

Question 33

Helper class to build a link for HATEOAS API?

Answer 33

Using ControllerLinkBuilder

Question 34

What HypermediaType is supported by Spring HATEOAX API?

Answer 34

Only HAL for now

Question 35

Example of building a method with HATEOAS response

Answer 35

1. Enable HATEOAS
   @Configuration
   @EnableHypermediaSupport(type=HypermediaType.HAL)
   public class MyConfig { }
2. Using @Controller for controller class (not @RestController)
3. Return Resource
   e.g.
   public @ResponseBody Resource method() {
   Links[] = …; // Some links (see previous slide)
   return new Resource(order, links);
   }

Question 36

What links does Spring HATEOAS support?

Answer 36

ATOM and HAL

Question 37

List out 10 arguments in a controller method

Answer 37

1. WebRequest, NativeWebRequest
2. ServletRequest, ServletResponse
3. HttpSession
4. Principal
5. HttpMethod
6. Locale
7. InputStream, Reader, OutputStream, Writer
8. @PathVariable, @RequestBody, @RequestParam, @MatrixVariable
9. @ModelAttribute, @RequestAttribute, @SessionAttribute, @RedirectAttribytes
10. HttpEntity
11. @RequestHeader