java如何解析双层json

Java如何解析双层JSON：实用指南与代码示例

在Java开发中，处理JSON数据是一项常见任务，特别是当面对嵌套的双层JSON结构时，本文将详细介绍如何在Java中解析双层JSON，包括使用不同库的方法、代码示例以及最佳实践。

理解双层JSON结构

双层JSON通常指一个JSON对象中包含另一个嵌套的JSON对象或数组。

{
  "user": {
    "name": "张三",
    "age": 30,
    "address": {
      "city": "北京",
      "district": "朝阳区"
    }
  },
  "orders": [
    {
      "id": "001",
      "product": "Java编程书",
      "price": 89.9
    },
    {
      "id": "002",
      "product": "Spring指南",
      "price": 79.9
    }
  ]
}

这个例子中，user是一个嵌套的JSON对象，orders是一个包含JSON对象的数组。

使用Gson解析双层JSON

Gson是Google提供的JSON处理库,以下是使用Gson解析双层JSON的步骤：

添加依赖

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.9</version>
</dependency>

创建实体类

public class Address {
    private String city;
    private String district;
    // getters and setters
}
public class User {
    private String name;
    private int age;
    private Address address;
    // getters and setters
}
public class Order {
    private String id;
    private String product;
    private double price;
    // getters and setters
}
public class ResponseData {
    private User user;
    private List<Order> orders;
    // getters and setters
}

解析JSON

import com.google.gson.Gson;
public class GsonParser {
    public static void main(String[] args) {
        String json = "{\"user\":{\"name\":\"张三\",\"age\":30,\"address\":{\"city\":\"北京\",\"district\":\"朝阳区\"}},\"orders\":[{\"id\":\"001\",\"product\":\"Java编程书\",\"price\":89.9},{\"id\":\"002\",\"product\":\"Spring指南\",\"price\":79.9}]}";
        Gson gson = new Gson();
        ResponseData responseData = gson.fromJson(json, ResponseData.class);
        // 访问数据
        System.out.println("用户名: " + responseData.getUser().getName());
        System.out.println("城市: " + responseData.getUser().getAddress().getCity());
        for (Order order : responseData.getOrders()) {
            System.out.println("订单ID: " + order.getId() + ", 产品: " + order.getProduct());
        }
    }
}

使用Jackson解析双层JSON

Jackson是另一个流行的JSON处理库,以下是使用Jackson的步骤：

添加依赖

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.13.0</version>
</dependency>

解析JSON

import com.fasterxml.jackson.databind.ObjectMapper;
public class JacksonParser {
    public static void main(String[] args) throws Exception {
        String json = "{\"user\":{\"name\":\"张三\",\"age\":30,\"address\":{\"city\":\"北京\",\"district\":\"朝阳区\"}},\"orders\":[{\"id\":\"001\",\"product\":\"Java编程书\",\"price\":89.9},{\"id\":\"002\",\"product\":\"Spring指南\",\"price\":79.9}]}";
        ObjectMapper mapper = new ObjectMapper();
        ResponseData responseData = mapper.readValue(json, ResponseData.class);
        // 访问数据
        System.out.println("用户名: " + responseData.getUser().getName());
        System.out.println("城市: " + responseData.getUser().getAddress().getCity());
        for (Order order : responseData.getOrders()) {
            System.out.println("订单ID: " + order.getId() + ", 产品: " + order.getProduct());
        }
    }
}

使用org.json解析双层JSON

org.json是一个轻量级的JSON处理库,以下是使用方法：

添加依赖

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20220320</version>
</dependency>

解析JSON

import org.json.JSONArray;
import org.json.JSONObject;
public class OrgJsonParser {
    public static void main(String[] args) {
        String json = "{\"user\":{\"name\":\"张三\",\"age\":30,\"address\":{\"city\":\"北京\",\"district\":\"朝阳区\"}},\"orders\":[{\"id\":\"001\",\"product\":\"Java编程书\",\"price\":89.9},{\"id\":\"002\",\"product\":\"Spring指南\",\"price\":79.9}]}";
        JSONObject jsonObject = new JSONObject(json);
        // 解析user对象
        JSONObject userObject = jsonObject.getJSONObject("user");
        String name = userObject.getString("name");
        JSONObject addressObject = userObject.getJSONObject("address");
        String city = addressObject.getString("city");
        System.out.println("用户名: " + name);
        System.out.println("城市: " + city);
        // 解析orders数组
        JSONArray ordersArray = jsonObject.getJSONArray("orders");
        for (int i = 0; i < ordersArray.length(); i++) {
            JSONObject orderObject = ordersArray.getJSONObject(i);
            String id = orderObject.getString("id");
            String product = orderObject.getString("product");
            System.out.println("订单ID: " + id + ", 产品: " + product);
        }
    }
}