Java topic notes ~ Fastjson overview

3.3 Mutual conversion between JSON string and Java object

After learning json, let's talk about the role of json.

In the future, we will use data in json format for front-end and back-end interactions. When the front end sends a request, if it is complex data, it will submit it to the back end in json; and if the back end needs to respond to some complex data, it also needs to respond the data back to the browser in json format.

At the back end, we need to focus on learning the following two parts of the operation:

Request data: Convert JSON string to Java object
Response data: Java object converted to JSON string

Next, I will introduce a set of API to you, which can realize the above two operations. This API isFastjson

3.3.1 Fastjson overview

FastjsonIt is a high-performance and fully functional JSONlibrary written in Java language provided by Alibaba. It is currently the fastest JSONlibrary in Java language, which can realize the mutual conversion between Javaobjects and strings.JSON

3.3.2 Using Fastjson

FastjsonThe use is also relatively simple, divided into the following three steps to complete

1. Import coordinates

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.62</version>
</dependency>

2. Java object to JSON

String jsonStr = JSON.toJSONString(obj);

To convert a Java object to a JSON string, you only need to use the static methods in the Fastjsonprovided class.JSONtoJSONString()

3. Convert JSON string to Java object

User user = JSON.parseObject(jsonStr, User.class);

To convert json to Java object, you only need to use the static method in the Fastjsonprovided class.JSONparseObject()

3.3.3 Code Demonstration

import coordinates
Create a class specially used to test the conversion between Java objects and JSON strings, the code is as follows:

public class FastJsonDemo {

    public static void main(String[] args) {
        //1. 将Java对象转为JSON字符串
        User user = new User();
        user.setId(1);
        user.setUsername("zhangsan");
        user.setPassword("123");

        String jsonString = JSON.toJSONString(user);
        System.out.println(jsonString);//{"id":1,"password":"123","username":"zhangsan"}


        //2. 将JSON字符串转为Java对象
        User u = JSON.parseObject("{\"id\":1,\"password\":\"123\",\"username\":\"zhangsan\"}", User.class);
        System.out.println(u);
    }
}