1. Introduction
When working with Jackson to serialize or deserialize Java objects to/from JSON, developers might encounter scenarios where the naming convention of JSON properties differs from the Java fields. The Jackson @JsonNaming annotation lets developers define naming strategies for the properties without changing the actual field names in Java. In this guide, we'll see how to apply this annotation and use a predefined naming strategy.
2. Example Steps
1. Add the necessary Jackson library dependencies to your project.
2. Create a Java class (POJO) for which you want to apply a specific naming strategy during serialization/deserialization.
3. Use the @JsonNaming annotation on the class and specify the desired naming strategy.
4. Create an instance of Jackson's ObjectMapper to perform serialization.
5. Output the serialized JSON.
3. Java Jackson @JsonNaming Example
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.annotation.JsonNaming;
public class JsonNamingExample {
public static void main(String[] args) {
// Create an instance of the User class
User user = new User("John", "Doe");
try {
ObjectMapper objectMapper = new ObjectMapper();
// Serialize the object to JSON
String jsonString = objectMapper.writeValueAsString(user);
System.out.println(jsonString);
} catch (Exception e) {
e.printStackTrace();
}
}
@JsonNaming(PropertyNamingStrategy.SnakeCaseStrategy.class)
static class User {
private String firstName;
private String lastName;
public User(String firstName, String lastName) {
this.firstName = firstName;
this.lastName = lastName;
}
// Getters, setters and other methods...
}
}
Output:
{"first_name":"John","last_name":"Doe"}
4. Step By Step Explanation
1. We created a User class with two fields - firstName and lastName.
2. We applied the @JsonNaming annotation on the User class and specified PropertyNamingStrategy.SnakeCaseStrategy.class as the desired naming strategy. This strategy will convert camel-case field names into snake-case JSON property names (e.g., firstName becomes first_name).
3. In the main method, an instance of the User class is created.
4. We use Jackson's ObjectMapper to serialize the User instance into a JSON string.
5. The resulting JSON string adheres to the snake-case naming convention, thanks to the @JsonNaming annotation.