Java中的序列化和反序列化

Java中序列化是我们开发中经常会用用到的方法之一，面试中可能会随口一问，以下简要说明序列化和反序列化的概念和例子。反序列化的问题请参考这里

概念

• 序列化：将java对象转为字节流，可以存储在磁盘或者网络传输，比如存储到redis或网络接口对接。
• 反序列化：将字节流转为java对象，比如网络对接的获取到的字符串转为java对象。

为什么要序列化

需要将java对象保存到redis中或者文本文件中，亦或者需要java对象在网络中传输。

序列化和反序列化的方法

• org.json
• json-lib
• jackson
• fastjson
• fastjson2
• gson

例子

这里使用fastjson包举例说明

java类转json字符串

import com.alibaba.fastjson.JSON;

import java.util.ArrayList;
import java.util.List;

/**
 *Java对象转json字符串
 */
public class StringToJSON {
    public static void main(String[] args) {
        //定义JSON字符串
        Employee e = new Employee("易学教程","male", 22);
        System.out.println(JSON.toJSONString(e));
        Employee e2 = new Employee("易学教程2","male", 23);
        Employee e3 = new Employee("易学教程3","male", 25);
        List<Employee> list = new ArrayList<>();
        list.add(e);
        list.add(e2);
        list.add(e3);
        System.out.println(JSON.toJSONString(list));

    }

    //JavaBean.java
    public static class  Employee{

        private String name;
        private String sex;
        private Integer age;

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

        public Employee(String name, String sex, Integer age) {
            this.name = name;
            this.sex = sex;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getSex() {
            return sex;
        }

        public void setSex(String sex) {
            this.sex = sex;
        }

        public Integer getAge() {
            return age;
        }

        public void setAge(Integer age) {
            this.age = age;
        }
    }
    
}

 json字符串转Java类

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.TypeReference;

import java.util.List;

/**
 *解析Json字符串反序列化为Java对象
 */
public class StringToJSON {


    public static void main(String[] args) {
        //定义JSON字符串
        String jsonStr = "{\"age\":22,\"name\":\"易学教程\",\"sex\":\"male\"}";
        Employee e = (Employee) JSON.parseObject(jsonStr, Employee.class);//简单java类解析
        System.out.println("json字符串转简单java对象:"+e.toString());
        //解析带有list的json字符串
        String jsonStr2 = "[{\"age\":22,\"name\":\"易学教程\",\"sex\":\"male\"},{\"age\":23,\"name\":\"易学教程2\",\"sex\":\"male\"},{\"age\":25,\"name\":\"易学教程3\",\"sex\":\"male\"}]";
        List<Employee> list =
                JSONObject.parseObject(jsonStr2, new TypeReference<List<Employee>>(){});
        System.out.println(list);

    }


    //JavaBean.java
    public static class  Employee{

        private String name;
        private String sex;
        private Integer age;

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

        public Employee() {
        }

        public Employee(String name, String sex, Integer age) {
            this.name = name;
            this.sex = sex;
            this.age = age;
        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getSex() {
            return sex;
        }

        public void setSex(String sex) {
            this.sex = sex;
        }

        public Integer getAge() {
            return age;
        }

        public void setAge(Integer age) {
            this.age = age;
        }
    }
}