implementation 'com.google.code.gson:gson:2.8.8'

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.8.8</version>
</dependency>

package com.e404.test

import com.google.gson.Gson
import com.google.gson.GsonBuilder
import java.io.FileInputStream
import java.io.FileOutputStream

fun main() {
    // 反序列化
    val stu: Student = FileInputStream("in.json").use {
        it.bufferedReader().use { br ->
            Gson().fromJson(br, Student::class.java)
        }
    }
    println("stu.name: ${stu.name}")
    println("stu.age: ${stu.age}")
    // 序列化
    FileOutputStream("out.json").use {
        it.bufferedWriter().use { bw ->
            // 要写入的json字符串
            // setPrettyPrinting 是生成带缩进的字符串
            val str: String = GsonBuilder().setPrettyPrinting().create().toJson(stu)
            bw.write(str)
        }
    }
}

/**
 * 必须要有无参的构造方法和每个参数的getter和setter
 *
 * (idea下setter可以用alt+insert快速生成)
 *
 * 否则会报错
 */
class Student(var name: String = "", var age: Int = 0)