[Spring] JSON Jackson Data Binding

Java JSON Data Binding

REST CRUD APIs(4)

• Data binding is the process of converting JSON data to a Java POJO
• mapping, sterilization 뭐 다 같은 말임
• Java POJO is just plain old Java object

JSON Data Binding with Jackson

• Spring uses the Jackson Project behind the scenes
• Jackson handles data binding between JSON and Java POJO
  • Spring Boot Starter Web automatically includes dependency for Jackson
• Details on Jackson Project:
  • https://github.com/FasterXML/jackson-databind

Jackson Data Binding

• By default, Jackson will call appropriate getter/setter method
  • The important thing is that it’ll actually use the getter and setter methods for handing some of this processing

JSON to Java POJO

• Convert JSON to Java POJO … call setter methods on POJO

• Note: Jackson calls the setXXX methods
• It does NOT access internal private fields directly

Java POJO to JSON

• Now let’s go the other direction
• Convert Java POJO to JSON … call getter methods on POJO

Spring and Jackson Support

• When building Spring REST applications
• Spring will automatically handle Jackson Integration
• JSON data being passed to REST controller is converted to POJO
• Java object being returned from REST controller is converted to JSON

Happens automatically behind scenes

Spring REST Service - Students

• Return a list of students

  GET -> /api/students -> Returns a list of students

Behind the scenes

Development Process

1. Create Java POJO class for Student
2. Create Spring REST Service using @RestController

Step 1: Create Java POJO class for Student

• Fields / Constructors / Getter/Setters

Step 2: Create @RestController

Convert Java POJO to JSON

• Our REST Service will return List<Student>
• Need to convert List<Student> to JSON
• Jackson can help up out with this…

Spring Boot and Jackson Support

• Spring Boot will automatically handle Jackson integration
  • Happens automatically behind the scenes
• JSON data being passed to REST controller is converted to Java POJO
• Java POJO being returned from REST controller is converted to JSON
  • Spring Boot Starter Web automatically includes dependency for Jackson

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