浅析Java中如何处理接口返回的JSON数据

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.2</version>
</dependency>

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.10.1</version>
</dependency>

{
  "code": 200,
  "msg": "请求成功",
  "data": {
    "id": 1001,
    "username": "zhangsan",
    "age": 25
  }
}

import lombok.Data;
// 整体返回结构
@Data
public class ApiResult {
    private Integer code;
    private String msg;
    private User data;
}
// data 里的用户对象
@Data
public class User {
    private Integer id;
    private String username;
    private Integer age;
}

import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonTest {
    public static void main(String[] args) throws Exception {
        // 接口返回的 JSON 字符串
        String json = "{\"code\":200,\"msg\":\"请求成功\",\"data\":{\"id\":1001,\"username\":\"zhangsan\",\"age\":25}}";

        ObjectMapper mapper = new ObjectMapper();
        ApiResult result = mapper.readValue(json, ApiResult.class);

        // 直接取值
        System.out.println(result.getCode());    // 200
        System.out.println(result.getMsg());     // 请求成功
        System.out.println(result.getData().getUsername()); // zhangsan
    }
}

import com.google.gson.Gson;

public class JsonTest {
    public static void main(String[] args) {
        String json = "{\"code\":200,\"msg\":\"请求成功\",\"data\":{\"id\":1001,\"username\":\"zhangsan\",\"age\":25}}";

        Gson gson = new Gson();
        ApiResult result = gson.fromJson(json, ApiResult.class);

        System.out.println(result.getCode());
        System.out.println(result.getData().getUsername());
    }
}

ObjectMapper mapper = new ObjectMapper();
Map<String, Object> map = mapper.readValue(json, Map.class);

int code = (int) map.get("code");
String msg = (String) map.get("msg");

Map<String, Object> data = (Map) map.get("data");
String username = (String) data.get("username");

Gson gson = new Gson();
Map<String, Object> map = gson.fromJson(json, Map.class);

double code = (double) map.get("code"); // Gson 数字默认 double
String username = (String) ((Map) map.get("data")).get("username");

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import com.fasterxml.jackson.databind.ObjectMapper;

public class PostWithJsonParse {
    public static void main(String[] args) throws Exception {
        String url = "https://httpbin.org/post";
        String jsonParams = "{\"username\":\"test\",\"password\":\"123456\"}";

        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(url))
                .POST(HttpRequest.BodyPublishers.ofString(jsonParams))
                .header("Content-Type", "application/json")
                .build();

        // 获取返回 JSON
        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
        String json = response.body();

        // 解析 JSON
        ObjectMapper mapper = new ObjectMapper();
        Map<String, Object> resultMap = mapper.readValue(json, Map.class);

        System.out.println("url: " + resultMap.get("url"));
        System.out.println("data: " + resultMap.get("data"));
    }
}