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Java中的 json文件

news 2025/7/20 0:41:23

在 Java 中处理 JSON 文件时，常用的库包括 Jackson、Gson 。

使用Jackson处理JSON文件

1. 引入Jackson依赖（如果你使用Maven）

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

2. 将JSON文件解析为Java对象

import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;
import java.io.IOException;

public class JsonExample {
    public static void main(String[] args) {
        ObjectMapper objectMapper = new ObjectMapper();
        
        try {
            // 假设有一个Student类
            Student student = objectMapper.readValue(new File("student.json"), Student.class);
            System.out.println(student);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class Student {
    private String name;
    private int age;

    // getters and setters

    @Override
    public String toString() {
        return "Student{name='" + name + "', age=" + age + "}";
    }
}

3. 将Java对象写入JSON文件

import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;
import java.io.IOException;

public class JsonExample {
    public static void main(String[] args) {
        ObjectMapper objectMapper = new ObjectMapper();
        
        Student student = new Student();
        student.setName("John");
        student.setAge(25);
        
        try {
            objectMapper.writeValue(new File("output.json"), student);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

使用Gson处理JSON文件

1. 引入Gson依赖（如果你使用Maven）

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.9</version> <!-- 请根据需要选择版本 -->
</dependency>

2. 将JSON文件解析为Java对象

import com.google.gson.Gson;
import java.io.FileReader;
import java.io.IOException;

public class JsonExample {
    public static void main(String[] args) {
        Gson gson = new Gson();
        
        try (FileReader reader = new FileReader("student.json")) {
            Student student = gson.fromJson(reader, Student.class);
            System.out.println(student);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

class Student {
    private String name;
    private int age;

    // getters and setters

    @Override
    public String toString() {
        return "Student{name='" + name + "', age=" + age + "}";
    }
}

3. 将Java对象写入JSON文件

import com.google.gson.Gson;
import java.io.FileWriter;
import java.io.IOException;

public class JsonExample {
    public static void main(String[] args) {
        Gson gson = new Gson();
        
        Student student = new Student();
        student.setName("John");
        student.setAge(25);
        
        try (FileWriter writer = new FileWriter("output.json")) {
            gson.toJson(student, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}