What Does Jackson Do in a Spring Boot Application?

#webdev #java #programming #springboot

➤ Serialization:

Converts Java objects → JSON
Used when sending responses from controllers.

@GetMapping("/user")
public User getUser() {
    return new User("John", 25);  // 👈 Spring uses Jackson to convert this to JSON
}

Result:

{
  "name": "John",
  "age": 25
}

➤ Deserialization:

Converts JSON → Java objects
Used when receiving data in request bodies.

@PostMapping("/user")
public ResponseEntity<?> createUser(@RequestBody User user) {
    // 👈 Jackson maps incoming JSON into a User object
    return ResponseEntity.ok("User created");
}

📦 Where Is Jackson in Spring Boot?

You don’t have to manually add Jackson — it’s included automatically with:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId> ✅ includes Jackson
</dependency>

Under the hood, Spring Boot uses:

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
</dependency>

⚙️ Customizing Jackson (Optional)

You can customize how JSON is handled:

@Bean
public ObjectMapper objectMapper() {
    ObjectMapper mapper = new ObjectMapper();
    mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    return mapper;
}

Or use annotations:

@JsonProperty("user_name")
private String name;

@JsonIgnore
private String password;

✅ Summary

Feature	Handled by Jackson in Spring Boot
Return JSON from controller	✅ Serialize Java → JSON
Accept JSON in request	✅ Deserialize JSON → Java
Customize format	✅ With annotations or config
Built-in with Spring Boot	✅ via `spring-boot-starter-web`