Message serialization in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to annotate a class for JSON serialization in Spring Boot.

Spring Boot

public class User {
    private String name;
    private int age;

    // getters and setters

    @[1]
    public String getName() {
        return name;
    }
}

Drag options to blanks, or click blank then click option'

AJsonProperty

BAutowired

CRequestMapping

DComponent

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Autowired instead of @JsonProperty

Confusing Spring annotations with Jackson annotations

The @JsonProperty annotation marks a method or field to be included in JSON serialization.

2fill in blank

medium

Complete the code to convert a Java object to JSON string using Jackson's ObjectMapper.

Spring Boot

ObjectMapper mapper = new ObjectMapper();
String json = mapper.[1](user);

Drag options to blanks, or click blank then click option'

AwriteValueAsString

BreadValue

CconvertValue

DreadTree

Attempts:

3 left

💡 Hint

Common Mistakes

Using readValue which is for deserialization

Using readTree which returns a JsonNode

The writeValueAsString method converts a Java object to a JSON string.

3fill in blank

hard

Fix the error in the code to deserialize JSON string to a Java object.

Spring Boot

User user = mapper.[1](json, User.class);

Drag options to blanks, or click blank then click option'

AwriteValueAsString

BwriteValue

CreadValue

DconvertValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using writeValueAsString which is for serialization

Using convertValue incorrectly without JSON string

The readValue method deserializes JSON string into a Java object.

4fill in blank

hard

Fill both blanks to create a REST controller method that returns JSON response.

Spring Boot

@RestController
public class UserController {

    @GetMapping("/user")
    public [1] getUser() {
        User user = new User("Alice", 30);
        return user;
    }

    public void setUser(@[2] User user) {
        // setter
    }
}

Drag options to blanks, or click blank then click option'

AUser

Bvoid

CJsonProperty

DRequestBody

Attempts:

3 left

💡 Hint

Common Mistakes

Using void as return type for JSON response

Missing @RequestBody on setter parameter

The method returns a User object which Spring Boot automatically serializes to JSON.

The @RequestBody annotation is used on setter to bind JSON request body to the method parameter.

5fill in blank

hard

Fill all three blanks to create a Map with filtered entries serialized to JSON.

Spring Boot

Map<String, Integer> result = Map.of("a", 1, "b", 2, "c", 3);
Map<String, Integer> filtered = result.entrySet().stream()
    .filter(e -> e.getValue() [1] 1)
    .collect(Collectors.[2](
        e -> e.getKey().[3](),
        e -> e.getValue()
    ));

Drag options to blanks, or click blank then click option'

A>

BtoMap

CtoUpperCase

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operator in filter

Using wrong collector method

Not converting keys to uppercase

The filter keeps entries with values greater than 1.

The collector gathers entries into a Map.

The keys are converted to uppercase strings.