FastJson - How to convert Java object to JSON and JSON to Java object

In this section, we will show you how to convert Java object to JSON and JSON to Java object with FastJson.

Note

Fastjson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Fastjson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

Note

JSON (JavaScript Object Notation) is a lightweight format that is used for data interchanging.

JSON is built on two structures: 

• A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array. 
• An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.

1. Download FastJson 

<dependency>
   <groupId>com.alibaba</groupId>
   <artifactId>fastjson</artifactId>
   <version>2.0.19</version>
</dependency>

2. JSON to Java Objects

A User POJO, later uses this for conversion.

User.java

public class User {

    private String name;
    private String email;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

Main.java

import com.alibaba.fastjson.JSON;

public class Main {

    public static void main(String[] args) {

        String json = "{\"name\":\"sibin\", " +
                "\"email\":\"sibin@gmail.in\"}";
        User user = JSON.parseObject(json, User.class);

        System.out.println(user);

    }
}

Console Output:

User{name='sibin', email='sibin@gmail.in'}

3. Java Objects to JSON

Main.java

import com.alibaba.fastjson.JSON;

public class Main {

    public static void main(String[] args) {

        User user = new User();

        user.setName("Sibin");
        user.setEmail("sibin@gmail.in");

        // Java objects to JSON
        String json = JSON.toJSONString(user);
        System.out.println(json);

        // Java objects to JSON, pretty-print
        String json2 = JSON.toJSONString(user, true);
        System.out.println(json2);

    }
}

Console Output:

{"email":"sibin@gmail.in","name":"Sibin"}
{
	"email":"sibin@gmail.in",
	"name":"Sibin"
}

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