Convert String JSON to Object and Object to String JSON in Java \ Spring Boot

Follow the steps below to convert a data from String JSON to Object and Object to String JSON in Java:

1. The first thing you'll need to do is, add the GSON library dependency to your application.
2. Create a JsonUtil.java Java class with the following two static methods:
• toObject(String data, Type type) - Method to convert data from String JSON to Object.
• toString(Object obj) - Method to convert data from Object to String JSON.

The following code shows how to do so:

import com.google.gson.Gson;
import java.lang.reflect.Type;

public class JsonUtil {

    public static <T> T toObject(String data, Type type) {
        Gson gson = new Gson();
        return gson.fromJson(data, type);
    }

    public static String toString(Object obj) {
        Gson gson = new Gson();
        return gson.toJson(obj);
    }

}

3. Example of using the above static methods:

import java.util.List;

public class JsonTest {

    public static void main(String[] args) {
        // Converting array JSON to List object
        String jsonArray = "[\"123\",\"456\",\"456\",\"232\"]";
        List<Long> array = JsonUtil.toObject(jsonArray, new TypeToken<List<Long>>() {}.getType());
        System.out.println(array);

        // Converting String JSON to User Object
        String strJsonObj = "{\"name\":\"Joe\", \"email\":\"[email protected]\"}";
        User user = JsonUtil.toObject(strJsonObj, User.class);
        System.out.println("Name=" + user.getName() + ", Email= " + user.getEmail());

        // Converting user object to String JSON
        String strJson = JsonUtil.toString(user);
        System.out.println(strJson);
    }
}

Output:

[123, 456, 456, 232]
Name=Joe, Email= [email protected]
{"name":"Joe","email":"[email protected]"}