在Java中读取和解析JSON文件的示例代码

{
  "name": "张三",        // 字符串类型
  "age": 28,            // 数字类型
  "isStudent": false,   // 布尔类型
  "courses": [          // 数组类型
    "Math",
    "Physics"
  ],
  "details": {          // 对象类型
    "address": "北京",
    "email": "zhangsan@example.com"
  }
}

<!-- Maven配置 -->
<dependency>
    <groupId>com.googlecode.json-simple</groupId>
    <artifactId>json-simple</artifactId>
    <version>1.1.1</version>
</dependency>

import org.json.simple.JSONObject;

public class JsonCreator {
    public static void main(String[] args) {
        JSONObject person = new JSONObject();
        person.put("name", "李四");
        person.put("age", 30);
        person.put("married", false);
        
        System.out.println(person.toJSONString());
        // 输出：{"name":"李四","age":30,"married":false}
    }
}

import org.json.simple.parser.JSONParser;
import org.json.simple.JSONObject;
import java.io.FileReader;

public class JsonReader {
    public static void main(String[] args) {
        JSONParser parser = new JSONParser();
        
        try (FileReader reader = new FileReader("data.json")) {
            JSONObject jsonObject = (JSONObject) parser.parse(reader);
            
            String name = (String) jsonObject.get("name");
            long age = (Long) jsonObject.get("age");
            System.out.println("姓名：" + name);
            System.out.println("年龄：" + age);
            
            // 解析嵌套数组
            JSONArray courses = (JSONArray) jsonObject.get("courses");
            System.out.println("课程列表：");
            for (Object course : courses) {
                System.out.println("\t- " + course);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

// 假设JSON结构：
// {
//   "students": [
//     {"name": "王五", "score": 85},
//     {"name": "赵六", "score": 92}
//   ]
// }

JSONArray students = (JSONArray) jsonObject.get("students");
for (Object obj : students) {
    JSONObject student = (JSONObject) obj;
    System.out.println("学生：" + student.get("name") + "，成绩：" + student.get("score"));
}

long safeAge = jsonObject.containsKey("age") 
    ? (Long) jsonObject.get("age") 
    : 0L; // 默认值处理

try (FileWriter file = new FileWriter("output.json")) {
    file.write(jsonObject.toJSONString());
    System.out.println("数据已保存到output.json");
} catch (IOException e) {
    e.printStackTrace();
}

// Spring Boot控制器示例
@RestController
public class UserController {
    @PostMapping("/users")
    public ResponseEntity<?> createUser(@Valid @RequestBody UserDto user) {
        // 自动将JSON转换为UserDto对象
        userService.save(user);
        return ResponseEntity.ok("用户创建成功");
    }
}