Spring Web

Question 1

What does @RestController do?

Answer 1

Annotates a controller class with:
1. @Controller
2. @ResponseBody

Question 2

1. What is a servlet?
2. What is Spring MVC’s main servlet called?

Answer 2

1. A servlet is a component of a servlet container used to handle HTTP requests and responses
2. DispatcherServlet

Question 3

What is Spring MVC?

Answer 3

A Spring framework for building web applications

Question 4

Spring MVC

Describe the lifecycle of an HTTP request

Question 5

What does @ResponseBody do?

Answer 5

Maps the return value of a controller method to an HTTP response body

Question 6

What does @RequestParam do?

Answer 6

Maps HTTP query parameters to controller method parameters. For example:

// localhost:8080/?name=gianmarco

@GetMapping
public String getName(@RequestParam String name) {
    return name;
  }
	
// returns gianmarco

Question 7

What does @PathVariable do?

Answer 7

Maps a URI template variable to a controller method parameter. For example:

// localhost:8080/1

@GetMapping("/{id}")
public int getId(@PathVariable int id) {
    return id;
}

// returns 1

Question 8

Why does Spring recommend using ResponseEntity instead of HttpServletResponse?

Answer 8

ResponseEntity can be used in a test environment

Question 9

Successful status codes for:

1. GET
2. POST
3. PUT
4. PATCH
5. DELETE

Answer 9

1. 200
2. 201
3. 204
4. 204
5. 204

Question 10

1. How does Spring MVC determine which message converter to use for an HTTP request?
2. How does Spring MVC determine which message converter to use for an HTTP response?

Answer 10

1. Content-Type header
2. Accept header

Question 11

When should a “Location” header be sent back in an HTTP response?

Answer 11

Whenever an HTTP POST request is successful

Question 12

What class does Spring recommend for building URIs?

Answer 12

ServletUriComponentsBuilder

Question 13

What does @ExceptionHandler do?

Answer 13

It marks a controller method as an exception handler. For example:

  @ExceptionHandler(Exception.class)
  public ProblemDetail handleExceptions() {
    return ProblemDetail.forStatus(HttpStatus.INTERNAL_SERVER_ERROR);
  }

Question 14

True or False

ResponseStatusException(…) can be thrown inside a controller method

Answer 14

True

Question 15

Can a controller method declare a Pageable parameter?

Answer 15

Yes
https://docs.spring.io/spring-data/commons/docs/current/reference/html/#core.web.basic.paging-and-sorting

Question 16

What does @RequestHeader do?

Answer 16

Maps HTTP request headers to a controller method parameter

Question 17

What are the 2 different ways to use @RequestMapping?

Answer 17

1. To map an HTTP request to a controller class
2. To map an HTTP request to a controller method

Question 18

What is the name of the Sring MVC starter?

Answer 18

spring-boot-starter-web

Question 19

How can you change the port of a Spring MVC application?

Answer 19

application.properties -> server.port = ?

Question 20

If you want to map HTTP HEAD, OPTIONS, and TRACE requests to a controller method, which annotation should you use?

Answer 20

@RequestMapping(method=?, path=?)

Question 21

Spring Boot

What bean should you use to instantiate a RestTemplate?

Answer 21

RestTemplateBuilder

Question 22

Does RestTemplate support streaming?

Answer 22

No. Consider using WebClient

Question 23

What are the 2 limitations of @ResponseStatus when used on a controller method?

Answer 23

1. Overrides status codes that may have been defined inside the controller method
2. Only works if the controller method does not throw an exception

Question 24

What is the main limitation of @ResponseStatus on a custom exception?

Answer 24

Returns an HTML error page making it unsuitable for RESTful applications. Consider using ResponseEntity instead

Question 25

What is a servlet container?

Answer 25

A servlet container is software that runs inside a web server and is used to manage threads, filters, and servlets

Question 26

Is it possible to map an HTTP request to a controller method by checking for specific headers, query parameters, or media types?

Answer 26

Yes. Look at @RequestMapping(…)

Question 27

What is the difference between @RequestBody vs ModelAttribute?

Answer 27

@RequestBody maps the body of an HTTP request to a POJO and @ModelAttribute maps query parameters to a POJO

Question 28

What is the difference between @Valid and @Validated?

Answer 28

@Valid enforces validation for all annotated fields. If any of the fields fail validation, the object is not created. @Validated enforces validation for either all annotated fields or specificed groups. This means it can be used for partial validation

Question 29

If both Spring MVC and Spring WebFlux are on the classpath, which one will take precedence?

Answer 29

Spring MVC

spring.main.web-application-type can be used to override this behavior

Question 30

What is the purpose of @ControllerAdvice?

Answer 30

To create a class bean that handles exceptions thrown by controllers. Class methods are annotated with @ExceptionHandler. For example:

@RestControllerAdvice // or @ControllerAdvice
public class GlobalExceptionHandler {

  @ExceptionHandler(HttpMessageConversionException.class)
  public ProblemDetail handleMessageConverterException(HttpMessageConversionException e) {
    return ProblemDetail.forStatus(HttpStatus.BAD_REQUEST);
  }

  @ExceptionHandler(Exception.class)
  public ProblemDetail handleExceptions() {
    return ProblemDetail.forStatus(HttpStatus.INTERNAL_SERVER_ERROR);
  }

Question 31

What 2 annotations makeup @RestControllerAdvice?

Answer 31

1. @ControllerAdvice (has @Component)
2. @ResponseBody