Java - convert object to JSON String with Jackson lib

In this short article, we would like to show how to convert any Java object to JSON, using an external Jackson library.

Quick solution:

// import com.fasterxml.jackson.core.JsonProcessingException;
// import com.fasterxml.jackson.databind.ObjectMapper;

ObjectMapper objectMapper = new ObjectMapper();

User userObject = new User("John", 21);
String userJson = objectMapper.writeValueAsString(userObject);

System.out.println(userJson);  // {"name":"John","age":21}

Hint: to know how to attach Jackson *.jar library to your project read this article.

Note: if you want to parse JSON to Object read this article.

Maven repository: https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind

Practical example

Full example of how to use Jackson library.

Main.java file content:

package examples;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Main {

    public static void main(String[] arg) throws JsonProcessingException {

        ObjectMapper objectMapper = new ObjectMapper();

        User userObject = new User("John", 21);
        String userJson = objectMapper.writeValueAsString(userObject);

        System.out.println(userJson); // {"name":"John","age":21}
    }
}

Example output:

{"name":"John","age":21}

User.java file content:

package examples;

public class User {

    private String name;
    private int age;

    // it is good to add no-arguments constructor too
    public User() {
        // nothing here ...
    }

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return this.name;
    }

    public int getAge() {
        return this.age;
    }
}

See also

1. Java - Jackson library installation instruction

2. Java - parse JSON to object with Jackson lib

References

1. Jackson Core - Maven Repository
2. Jackson Databind - Maven Repository