Gson转换json数据为对象

可以通过Gson使用两种方法，将json字符串转换为对象，以下面该段报文做测试

{
    "id": 84041462,
    "lastName": "小华",
    "age":32,
    "balance":666255.32,
    "hobbyDesc": {
        "subject": "数学",
        "score":25,
        "sport_desc":"跑步有益健康"
    }    
}

1. 创建实体类，通过 fromJson方法将json数据封装进对象中

如上，将上面报文按层次解析并创建两个对象

import com.google.gson.annotations.SerializedName;

public class HobbyDesc {

    private String subject;
    private int score;
    @SerializedName("sport_desc")
    private String sportDesc;

    //***

public class Account {
    private String id;
    private String lastName;
    private int age;
    private double balance;
    private HobbyDesc hobbyDesc;
    
    //***

解析

String jsonStr = "{\n" +
                "\t\"id\": 84041462,\n" +
                "\t\"lastName\": \"小华\",\n" +
                "\t\"age\":32,\n" +
                "\t\"balance\":666255.32,\n" +
                "\t\"hobbyDesc\": {\n" +
                "\t\t\"subject\": \"数学\",\n" +
                "\t\t\"score\":25,\n" +
                "\t\t\"sport_desc\":\"跑步有益健康\"\n" +
                "\t}\n" +
                "\t\n" +
                "}";

Account account = new Gson().fromJson(jsonStr,Account.class);

同时也可以看到，对象中定义为字符串类型的字段也可以接受json串的数值类型，没有转换问题。

2. 解析为jsonObject对象

直接使用Gson API解析

String jsonStr = "{\n" +
                "\t\"id\": 84041462,\n" +
                "\t\"lastName\": \"小华\",\n" +
                "\t\"age\":32,\n" +
                "\t\"balance\":666255.32,\n" +
                "\t\"hobbyDesc\": {\n" +
                "\t\t\"subject\": \"数学\",\n" +
                "\t\t\"score\":25,\n" +
                "\t\t\"sport_desc\":\"跑步有益健康\"\n" +
                "\t}\n" +
                "\t\n" +
                "}";
JsonObject jsonObject = (JsonObject) new JsonParser().parse(jsonStr); 
    
System.out.println("id <getAsInt> = "+jsonObject.get("id").getAsInt());//id <getAsInt> = 84041462
System.out.println("id <getAsString> = "+jsonObject.get("id").getAsString());//id <getAsString> = 84041462
System.out.println("position = "+ jsonObject.get("hobbyDesc").getAsJsonObject().get("sport_desc").getAsString());//position = 跑步有益健康

参照jsonObject结构，可以了解Gson这种封装对象的方式，如果仅仅是取某值的话，可以采用这种方式，可以节约大量时间