Java序列化和Protobuf

序列化

原理无非将对象压缩成字符流，需要的时候再取出来；

这种情况在分布式用的比较多，类似的Xml和Json也可以实现这种效果；

---

下面放一个Java序列化的例子

1.创建实例化对象

package com.bean;


import java.io.Serializable;
import java.util.List;

/**
 * @author: jane
 * @CreateTime: 2020/5/11
 * @Description:
 */
public class MyProto implements Serializable {
    int userID;
    String userName;
    List<String> hobby;
    public MyProto(int userID, String userName, List<String> hobby){
        this.userID = userID;
        this.userName = userName;
        this.hobby = hobby;
    }

    @Override
    public String toString() {
        return "MyProto{" +
                "userID=" + userID +
                ", userName='" + userName + '\'' +
                ", hobby=" + hobby +
                '}';
    }
}

如果有不希望被序列化的属性，可以加上transient；

2.编写测试

package com.serializable;

import com.bean.MyProto;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author: jane
 * @CreateTime: 2020/5/11
 * @Description:
 */
public class SerializableTest {
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        List<String> hobby = new ArrayList<>();
        hobby.add("Programming");
        hobby.add("Reading");
        hobby.add("Playing Games");
        MyProto proto = new MyProto(666, "Jane", hobby);
        System.out.println("Before encode:"+proto.toString());

        FileOutputStream fos = new FileOutputStream(new File("src/main/resources/serial.out"));
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        oos.writeObject(proto);

        FileInputStream fis = new FileInputStream(new File("src/main/resources/serial.out"));
        ObjectInputStream ois = new ObjectInputStream(fis);
        MyProto proto2 = (MyProto)ois.readObject();

        System.out.println("After decode:"+proto2.toString());
    }
}

3.输出结果，符合预期

Before encode:MyProto{userID=666, userName='Jane', hobby=[Programming, Reading, Playing Games]}
After decode:MyProto{userID=666, userName='Jane', hobby=[Programming, Reading, Playing Games]}

---

Protobuf

Protobuf也是用于序列化的，而且Protobuf的效率比较高，适合常见语言；

Java自带的Serializable就比较专一了。。。

下面演示Windows版的例子

1.下载

https://github.com/protocolbuffers/protobuf/releases/tag/v3.11.4

里面的protoc.exe是关键

2.编写MyProto.proto

option java_package = "com.protobuf";
option java_outer_classname = "MyProtoName";

message MyProto{
    required int32 userID = 1;
    required string userName = 2;
    repeated string hobby = 3;
}

3.Cmd下，通过Protobuf生成Java文件

protoc.exe --java_out=.\ .\MyProto.proto

4.把生成的Java文件放到项目对应位置，编写测试

package com.protobuf;

import com.google.protobuf.InvalidProtocolBufferException;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

/**
 * @author: jane
 * @CreateTime: 2020/5/11
 * @Description:
 */
public class ProtoTest {
    public static void main(String[] args) throws InvalidProtocolBufferException {
        MyProtoName.MyProto proto = create();
        System.out.println("Before encode:");
        System.out.println(proto.toString());
        MyProtoName.MyProto proto2 = decode(encode(proto));
        System.out.println("After decode:");
        System.out.println(proto2.toString());
        System.out.println(proto.equals(proto2));
    }
    private static MyProtoName.MyProto create(){
        MyProtoName.MyProto.Builder builder = MyProtoName.MyProto.newBuilder();
        builder.setUserID(777);
        builder.setUserName("Jayying");
        List<String> hobby = new ArrayList<>();
        hobby.add("Programming");
        hobby.add("Reading");
        hobby.add("Playing Games");
        builder.addAllHobby(hobby);
        return builder.build();
    }
    private static byte[] encode(MyProtoName.MyProto proto){
        return proto.toByteArray();
    }
    private static MyProtoName.MyProto decode(byte[] code) throws InvalidProtocolBufferException {
        return MyProtoName.MyProto.parseFrom(code);
    }
}

5.结果输出，符合预期

Before encode:
userID: 777
userName: "Jayying"
hobby: "Programming"
hobby: "Reading"
hobby: "Playing Games"

After decode:
userID: 777
userName: "Jayying"
hobby: "Programming"
hobby: "Reading"
hobby: "Playing Games"

true