Java中的序列化、反序列化-serializable和serialversionUID

在Java项目中，我们经常对实体类进行implement serializable，在实体类中又加上一句

private static final long serialVersionUID = 5177165015785112433L;

最开始只知道是跟实体类的序列化有关，但是没有深究，昨天突然想起来了，于是想知道到底是什么东西，在这里小手一抖，记录一下......

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这里补充一下小知识：

　　1、序列化、反序列化：

　　序列化：将对象转化为字节序列的过程；

　　反序列化：将字节序列反转成对象的过程。  具体看到下面的例子就明白了

　　2、在io流中，有ObjectInputStream、ObjectoutputStream，这俩个在用在实体对象时，要求对象必须实现serializable，表示该对象可被序列化。

 一、首先我们尝试一下，实体类不进行implement Serializable，分别对实体类进行序列化和反序列化

　　咱的实体类：

package com.example.io.serializable;

import lombok.Data;

import java.io.Serializable;

/**
 * @program: io
 * @description:
 * @author: liuqj
 * @create: 2020-06-17 09:41
 **/
@Data
public class Book {

    private int id;
    private String name;
    private Double price;
}

 

 测试： 

    package com.example.io.serializable;

    import java.io.*;

    /**
     * @program: io
     * @description:
     * @author: liuqj
     * @create: 2020-06-17 09:43
     **/
    public class TestSerializable {
        public static void main(String[] args) throws IOException, ClassNotFoundException {
            serializable();
            deserializable();
    }
    static void serializable () throws IOException {
        Book book = new Book();
        book.setId(1);
        book.setName("从大爆炸到黑洞");
        book.setPrice(100.00);
        ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(new File("D:\\Personal\\JavaProject\\io\\serializable.txt")));
        outputStream.writeObject(book);
　　　　　　 outputStream.clouse();
        System.out.println("序列化成功");
    }
    static void deserializable() throws IOException, ClassNotFoundException {
        ObjectInputStream inputStream = new ObjectInputStream(new FileInputStream(new File("D:\\Personal\\JavaProject\\io\\serializable.txt")));
        Book book = (Book) inputStream.readObject();
　　　　　　 inputStream.clouse();
        System.out.println(book);
    }

 

运行结果：

 

 

 

 可以看到如果不对实体类进行implement Serializable，那么进行序列化的时候就会报错。

 

二、对实体进行implement Serializable，但不加serialversionUID。

@Data
public class Book implements Serializable{

    private int id;
    private String name;
    private Double price;
}

 

1、直接进行序列化、反序列化

　　运行结果：

　　 序列化成功 2 Book(id=1, name=从大爆炸到黑洞, price=100.0) 3 4 Process finished with exit code 0 

2、先进行序列化，然后修改(删除)对象中的属性，再进行反序列化

D:\Work\Jdk\bin\java.exe "-javaagent:D:\Work\Idea\IntelliJ IDEA 2019.3.4\lib\idea_rt.jar=54850:D:\Work\Idea\IntelliJ IDEA 2019.3.4\bin" -Dfile.encoding=UTF-8 -classpath D:\Work\Jdk\jre\lib\charsets.jar;D:\Work\Jdk\jre\lib\deploy.jar;D:\Work\Jdk\jre\lib\ext\access-bridge-64.jar;D:\Work\Jdk\jre\lib\ext\cldrdata.jar;D:\Work\Jdk\jre\lib\ext\dnsns.jar;D:\Work\Jdk\jre\lib\ext\jaccess.jar;D:\Work\Jdk\jre\lib\ext\jfxrt.jar;D:\Work\Jdk\jre\lib\ext\localedata.jar;D:\Work\Jdk\jre\lib\ext\nashorn.jar;D:\Work\Jdk\jre\lib\ext\sunec.jar;D:\Work\Jdk\jre\lib\ext\sunjce_provider.jar;D:\Work\Jdk\jre\lib\ext\sunmscapi.jar;D:\Work\Jdk\jre\lib\ext\sunpkcs11.jar;D:\Work\Jdk\jre\lib\ext\zipfs.jar;D:\Work\Jdk\jre\lib\javaws.jar;D:\Work\Jdk\jre\lib\jce.jar;D:\Work\Jdk\jre\lib\jfr.jar;D:\Work\Jdk\jre\lib\jfxswt.jar;D:\Work\Jdk\jre\lib\jsse.jar;D:\Work\Jdk\jre\lib\management-agent.jar;D:\Work\Jdk\jre\lib\plugin.jar;D:\Work\Jdk\jre\lib\resources.jar;D:\Work\Jdk\jre\lib\rt.jar;D:\Personal\JavaProject\io\target\classes;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-data-jdbc\2.3.1.RELEASE\spring-boot-starter-data-jdbc-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-jdbc\2.3.1.RELEASE\spring-boot-starter-jdbc-2.3.1.RELEASE.jar;D:\Work\Maven\repository\com\zaxxer\HikariCP\3.4.5\HikariCP-3.4.5.jar;D:\Work\Maven\repository\org\springframework\spring-jdbc\5.2.7.RELEASE\spring-jdbc-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-jdbc\2.0.1.RELEASE\spring-data-jdbc-2.0.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-relational\2.0.1.RELEASE\spring-data-relational-2.0.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-commons\2.3.1.RELEASE\spring-data-commons-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-tx\5.2.7.RELEASE\spring-tx-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-context\5.2.7.RELEASE\spring-context-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-aop\5.2.7.RELEASE\spring-aop-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-expression\5.2.7.RELEASE\spring-expression-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-beans\5.2.7.RELEASE\spring-beans-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter\2.3.1.RELEASE\spring-boot-starter-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot\2.3.1.RELEASE\spring-boot-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-autoconfigure\2.3.1.RELEASE\spring-boot-autoconfigure-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-logging\2.3.1.RELEASE\spring-boot-starter-logging-2.3.1.RELEASE.jar;D:\Work\Maven\repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;D:\Work\Maven\repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;D:\Work\Maven\repository\org\apache\logging\log4j\log4j-to-slf4j\2.13.3\log4j-to-slf4j-2.13.3.jar;D:\Work\Maven\repository\org\apache\logging\log4j\log4j-api\2.13.3\log4j-api-2.13.3.jar;D:\Work\Maven\repository\org\slf4j\jul-to-slf4j\1.7.30\jul-to-slf4j-1.7.30.jar;D:\Work\Maven\repository\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;D:\Work\Maven\repository\org\yaml\snakeyaml\1.26\snakeyaml-1.26.jar;D:\Work\Maven\repository\org\springframework\spring-core\5.2.7.RELEASE\spring-core-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-jcl\5.2.7.RELEASE\spring-jcl-5.2.7.RELEASE.jar com.example.io.serializable.TestSerializable
Exception in thread "main" java.io.InvalidClassException: com.example.io.serializable.Book; 
　　　　local class incompatible: stream classdesc serialVersionUID = -1858406188231479520, local class serialVersionUID = 4049423394988101590
    at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:616)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1843)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1713)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2000)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1535)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:422)
    at com.example.io.serializable.TestSerializable.deserializable(TestSerializable.java:27)
    at com.example.io.serializable.TestSerializable.main(TestSerializable.java:14)

Process finished with exit code 1

 

可以看到反序列化失败，报错中显示，流中的UID和本地的UID不一致导致的反序列化失败，但我们本地并没有加serialversionUID啊？

是酱紫滴，虽然我们没加，但是实现了implement Serializable，该接口会帮我们在本地生成一个UID，但这种默认生成的方式，在进行反序列化时不顶用了，

会出现InvalidClassException异常，原因我也木知。(猜测大概是：序列化时(本地->流)，会生成一次UID给到序列化后的内容中，反序列化时(流->本地)又再次生成了一次UID给本地，

此时，流中的UID和新生成的本地UID不同，所以导致无法反序列化)

 

三、实体类implement Serializable 且加上serialversionUID

public class Book implements Serializable{

    private static final Long serialVersionUID = -1858406188231479520L;  //注意final不能少，不然本地的UID在反序列化的过程中会被更改，这句代码就相当于没加
    private int id;
    private String name;
    private Double price;
}

 

1、先直接进行序列化、反序列化

　　结果显示：nice

D:\Work\Jdk\bin\java.exe "-javaagent:D:\Work\Idea\IntelliJ IDEA 2019.3.4\lib\idea_rt.jar=55570:D:\Work\Idea\IntelliJ IDEA 2019.3.4\bin" -Dfile.encoding=UTF-8 -classpath D:\Work\Jdk\jre\lib\charsets.jar;D:\Work\Jdk\jre\lib\deploy.jar;D:\Work\Jdk\jre\lib\ext\access-bridge-64.jar;D:\Work\Jdk\jre\lib\ext\cldrdata.jar;D:\Work\Jdk\jre\lib\ext\dnsns.jar;D:\Work\Jdk\jre\lib\ext\jaccess.jar;D:\Work\Jdk\jre\lib\ext\jfxrt.jar;D:\Work\Jdk\jre\lib\ext\localedata.jar;D:\Work\Jdk\jre\lib\ext\nashorn.jar;D:\Work\Jdk\jre\lib\ext\sunec.jar;D:\Work\Jdk\jre\lib\ext\sunjce_provider.jar;D:\Work\Jdk\jre\lib\ext\sunmscapi.jar;D:\Work\Jdk\jre\lib\ext\sunpkcs11.jar;D:\Work\Jdk\jre\lib\ext\zipfs.jar;D:\Work\Jdk\jre\lib\javaws.jar;D:\Work\Jdk\jre\lib\jce.jar;D:\Work\Jdk\jre\lib\jfr.jar;D:\Work\Jdk\jre\lib\jfxswt.jar;D:\Work\Jdk\jre\lib\jsse.jar;D:\Work\Jdk\jre\lib\management-agent.jar;D:\Work\Jdk\jre\lib\plugin.jar;D:\Work\Jdk\jre\lib\resources.jar;D:\Work\Jdk\jre\lib\rt.jar;D:\Personal\JavaProject\io\target\classes;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-data-jdbc\2.3.1.RELEASE\spring-boot-starter-data-jdbc-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-jdbc\2.3.1.RELEASE\spring-boot-starter-jdbc-2.3.1.RELEASE.jar;D:\Work\Maven\repository\com\zaxxer\HikariCP\3.4.5\HikariCP-3.4.5.jar;D:\Work\Maven\repository\org\springframework\spring-jdbc\5.2.7.RELEASE\spring-jdbc-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-jdbc\2.0.1.RELEASE\spring-data-jdbc-2.0.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-relational\2.0.1.RELEASE\spring-data-relational-2.0.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-commons\2.3.1.RELEASE\spring-data-commons-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-tx\5.2.7.RELEASE\spring-tx-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-context\5.2.7.RELEASE\spring-context-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-aop\5.2.7.RELEASE\spring-aop-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-expression\5.2.7.RELEASE\spring-expression-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-beans\5.2.7.RELEASE\spring-beans-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter\2.3.1.RELEASE\spring-boot-starter-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot\2.3.1.RELEASE\spring-boot-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-autoconfigure\2.3.1.RELEASE\spring-boot-autoconfigure-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-logging\2.3.1.RELEASE\spring-boot-starter-logging-2.3.1.RELEASE.jar;D:\Work\Maven\repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;D:\Work\Maven\repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;D:\Work\Maven\repository\org\apache\logging\log4j\log4j-to-slf4j\2.13.3\log4j-to-slf4j-2.13.3.jar;D:\Work\Maven\repository\org\apache\logging\log4j\log4j-api\2.13.3\log4j-api-2.13.3.jar;D:\Work\Maven\repository\org\slf4j\jul-to-slf4j\1.7.30\jul-to-slf4j-1.7.30.jar;D:\Work\Maven\repository\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;D:\Work\Maven\repository\org\yaml\snakeyaml\1.26\snakeyaml-1.26.jar;D:\Work\Maven\repository\org\springframework\spring-core\5.2.7.RELEASE\spring-core-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-jcl\5.2.7.RELEASE\spring-jcl-5.2.7.RELEASE.jar com.example.io.serializable.TestSerializable
序列化成功
Book(id=1, name=从大爆炸到黑洞, price=100.0)

Process finished with exit code 0

 

2、先序列化，然后删除(修改)对象中某一个属性，再进行反序列化

　　删除一个属性后的实体类

@Data
public class Book implements Serializable{

    private static final long serialVersionUID = -1858406188231479520L;

    private int id;
    private String name;
    //private Double price;
}

 

　　反序列化

D:\Work\Jdk\bin\java.exe "-javaagent:D:\Work\Idea\IntelliJ IDEA 2019.3.4\lib\idea_rt.jar=56290:D:\Work\Idea\IntelliJ IDEA 2019.3.4\bin" -Dfile.encoding=UTF-8 -classpath D:\Work\Jdk\jre\lib\charsets.jar;D:\Work\Jdk\jre\lib\deploy.jar;D:\Work\Jdk\jre\lib\ext\access-bridge-64.jar;D:\Work\Jdk\jre\lib\ext\cldrdata.jar;D:\Work\Jdk\jre\lib\ext\dnsns.jar;D:\Work\Jdk\jre\lib\ext\jaccess.jar;D:\Work\Jdk\jre\lib\ext\jfxrt.jar;D:\Work\Jdk\jre\lib\ext\localedata.jar;D:\Work\Jdk\jre\lib\ext\nashorn.jar;D:\Work\Jdk\jre\lib\ext\sunec.jar;D:\Work\Jdk\jre\lib\ext\sunjce_provider.jar;D:\Work\Jdk\jre\lib\ext\sunmscapi.jar;D:\Work\Jdk\jre\lib\ext\sunpkcs11.jar;D:\Work\Jdk\jre\lib\ext\zipfs.jar;D:\Work\Jdk\jre\lib\javaws.jar;D:\Work\Jdk\jre\lib\jce.jar;D:\Work\Jdk\jre\lib\jfr.jar;D:\Work\Jdk\jre\lib\jfxswt.jar;D:\Work\Jdk\jre\lib\jsse.jar;D:\Work\Jdk\jre\lib\management-agent.jar;D:\Work\Jdk\jre\lib\plugin.jar;D:\Work\Jdk\jre\lib\resources.jar;D:\Work\Jdk\jre\lib\rt.jar;D:\Personal\JavaProject\io\target\classes;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-data-jdbc\2.3.1.RELEASE\spring-boot-starter-data-jdbc-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-jdbc\2.3.1.RELEASE\spring-boot-starter-jdbc-2.3.1.RELEASE.jar;D:\Work\Maven\repository\com\zaxxer\HikariCP\3.4.5\HikariCP-3.4.5.jar;D:\Work\Maven\repository\org\springframework\spring-jdbc\5.2.7.RELEASE\spring-jdbc-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-jdbc\2.0.1.RELEASE\spring-data-jdbc-2.0.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-relational\2.0.1.RELEASE\spring-data-relational-2.0.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\data\spring-data-commons\2.3.1.RELEASE\spring-data-commons-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-tx\5.2.7.RELEASE\spring-tx-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-context\5.2.7.RELEASE\spring-context-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-aop\5.2.7.RELEASE\spring-aop-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-expression\5.2.7.RELEASE\spring-expression-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-beans\5.2.7.RELEASE\spring-beans-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\slf4j\slf4j-api\1.7.30\slf4j-api-1.7.30.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter\2.3.1.RELEASE\spring-boot-starter-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot\2.3.1.RELEASE\spring-boot-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-autoconfigure\2.3.1.RELEASE\spring-boot-autoconfigure-2.3.1.RELEASE.jar;D:\Work\Maven\repository\org\springframework\boot\spring-boot-starter-logging\2.3.1.RELEASE\spring-boot-starter-logging-2.3.1.RELEASE.jar;D:\Work\Maven\repository\ch\qos\logback\logback-classic\1.2.3\logback-classic-1.2.3.jar;D:\Work\Maven\repository\ch\qos\logback\logback-core\1.2.3\logback-core-1.2.3.jar;D:\Work\Maven\repository\org\apache\logging\log4j\log4j-to-slf4j\2.13.3\log4j-to-slf4j-2.13.3.jar;D:\Work\Maven\repository\org\apache\logging\log4j\log4j-api\2.13.3\log4j-api-2.13.3.jar;D:\Work\Maven\repository\org\slf4j\jul-to-slf4j\1.7.30\jul-to-slf4j-1.7.30.jar;D:\Work\Maven\repository\jakarta\annotation\jakarta.annotation-api\1.3.5\jakarta.annotation-api-1.3.5.jar;D:\Work\Maven\repository\org\yaml\snakeyaml\1.26\snakeyaml-1.26.jar;D:\Work\Maven\repository\org\springframework\spring-core\5.2.7.RELEASE\spring-core-5.2.7.RELEASE.jar;D:\Work\Maven\repository\org\springframework\spring-jcl\5.2.7.RELEASE\spring-jcl-5.2.7.RELEASE.jar com.example.io.serializable.TestSerializable
Book(id=1, name=从大爆炸到黑洞)

Process finished with exit code 0

 

 

 总结：

（1）对实体进行implement Serializable，表示该对象可以进行序列化；

（2）只进行implement Serializable，每次进行序列化时会自动生成一个serialVersionUID保证序列化的进行，

　　在实体对象没有改变过的前提下，可以进行反序列化，如果对象属性改变过，反序列化时再次生成的UID和序列化时生成的UID不同无法进行反序列化；

（3）在进行implement Serializable后，加上private static final long serialVersionUID = xxxL; 可保证序列化之后，即使对实体对象做出了改变仍可以进行反序列化。