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:WorkJdkinjava.exe "-javaagent:D:WorkIdeaIntelliJ IDEA 2019.3.4libidea_rt.jar=54850:D:WorkIdeaIntelliJ IDEA 2019.3.4in" -Dfile.encoding=UTF-8 -classpath D:WorkJdkjrelibcharsets.jar;D:WorkJdkjrelibdeploy.jar;D:WorkJdkjrelibextaccess-bridge-64.jar;D:WorkJdkjrelibextcldrdata.jar;D:WorkJdkjrelibextdnsns.jar;D:WorkJdkjrelibextjaccess.jar;D:WorkJdkjrelibextjfxrt.jar;D:WorkJdkjrelibextlocaledata.jar;D:WorkJdkjrelibext
ashorn.jar;D:WorkJdkjrelibextsunec.jar;D:WorkJdkjrelibextsunjce_provider.jar;D:WorkJdkjrelibextsunmscapi.jar;D:WorkJdkjrelibextsunpkcs11.jar;D:WorkJdkjrelibextzipfs.jar;D:WorkJdkjrelibjavaws.jar;D:WorkJdkjrelibjce.jar;D:WorkJdkjrelibjfr.jar;D:WorkJdkjrelibjfxswt.jar;D:WorkJdkjrelibjsse.jar;D:WorkJdkjrelibmanagement-agent.jar;D:WorkJdkjrelibplugin.jar;D:WorkJdkjrelib
esources.jar;D:WorkJdkjrelib
t.jar;D:PersonalJavaProjectio	argetclasses;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-data-jdbc2.3.1.RELEASEspring-boot-starter-data-jdbc-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-jdbc2.3.1.RELEASEspring-boot-starter-jdbc-2.3.1.RELEASE.jar;D:WorkMaven
epositorycomzaxxerHikariCP3.4.5HikariCP-3.4.5.jar;D:WorkMaven
epositoryorgspringframeworkspring-jdbc5.2.7.RELEASEspring-jdbc-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-jdbc2.0.1.RELEASEspring-data-jdbc-2.0.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-relational2.0.1.RELEASEspring-data-relational-2.0.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-commons2.3.1.RELEASEspring-data-commons-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-tx5.2.7.RELEASEspring-tx-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-context5.2.7.RELEASEspring-context-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-aop5.2.7.RELEASEspring-aop-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-expression5.2.7.RELEASEspring-expression-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-beans5.2.7.RELEASEspring-beans-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgslf4jslf4j-api1.7.30slf4j-api-1.7.30.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter2.3.1.RELEASEspring-boot-starter-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot2.3.1.RELEASEspring-boot-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-autoconfigure2.3.1.RELEASEspring-boot-autoconfigure-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-logging2.3.1.RELEASEspring-boot-starter-logging-2.3.1.RELEASE.jar;D:WorkMaven
epositorychqoslogbacklogback-classic1.2.3logback-classic-1.2.3.jar;D:WorkMaven
epositorychqoslogbacklogback-core1.2.3logback-core-1.2.3.jar;D:WorkMaven
epositoryorgapachelogginglog4jlog4j-to-slf4j2.13.3log4j-to-slf4j-2.13.3.jar;D:WorkMaven
epositoryorgapachelogginglog4jlog4j-api2.13.3log4j-api-2.13.3.jar;D:WorkMaven
epositoryorgslf4jjul-to-slf4j1.7.30jul-to-slf4j-1.7.30.jar;D:WorkMaven
epositoryjakartaannotationjakarta.annotation-api1.3.5jakarta.annotation-api-1.3.5.jar;D:WorkMaven
epositoryorgyamlsnakeyaml1.26snakeyaml-1.26.jar;D:WorkMaven
epositoryorgspringframeworkspring-core5.2.7.RELEASEspring-core-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-jcl5.2.7.RELEASEspring-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:WorkJdkinjava.exe "-javaagent:D:WorkIdeaIntelliJ IDEA 2019.3.4libidea_rt.jar=55570:D:WorkIdeaIntelliJ IDEA 2019.3.4in" -Dfile.encoding=UTF-8 -classpath D:WorkJdkjrelibcharsets.jar;D:WorkJdkjrelibdeploy.jar;D:WorkJdkjrelibextaccess-bridge-64.jar;D:WorkJdkjrelibextcldrdata.jar;D:WorkJdkjrelibextdnsns.jar;D:WorkJdkjrelibextjaccess.jar;D:WorkJdkjrelibextjfxrt.jar;D:WorkJdkjrelibextlocaledata.jar;D:WorkJdkjrelibext
ashorn.jar;D:WorkJdkjrelibextsunec.jar;D:WorkJdkjrelibextsunjce_provider.jar;D:WorkJdkjrelibextsunmscapi.jar;D:WorkJdkjrelibextsunpkcs11.jar;D:WorkJdkjrelibextzipfs.jar;D:WorkJdkjrelibjavaws.jar;D:WorkJdkjrelibjce.jar;D:WorkJdkjrelibjfr.jar;D:WorkJdkjrelibjfxswt.jar;D:WorkJdkjrelibjsse.jar;D:WorkJdkjrelibmanagement-agent.jar;D:WorkJdkjrelibplugin.jar;D:WorkJdkjrelib
esources.jar;D:WorkJdkjrelib
t.jar;D:PersonalJavaProjectio	argetclasses;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-data-jdbc2.3.1.RELEASEspring-boot-starter-data-jdbc-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-jdbc2.3.1.RELEASEspring-boot-starter-jdbc-2.3.1.RELEASE.jar;D:WorkMaven
epositorycomzaxxerHikariCP3.4.5HikariCP-3.4.5.jar;D:WorkMaven
epositoryorgspringframeworkspring-jdbc5.2.7.RELEASEspring-jdbc-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-jdbc2.0.1.RELEASEspring-data-jdbc-2.0.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-relational2.0.1.RELEASEspring-data-relational-2.0.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-commons2.3.1.RELEASEspring-data-commons-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-tx5.2.7.RELEASEspring-tx-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-context5.2.7.RELEASEspring-context-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-aop5.2.7.RELEASEspring-aop-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-expression5.2.7.RELEASEspring-expression-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-beans5.2.7.RELEASEspring-beans-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgslf4jslf4j-api1.7.30slf4j-api-1.7.30.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter2.3.1.RELEASEspring-boot-starter-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot2.3.1.RELEASEspring-boot-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-autoconfigure2.3.1.RELEASEspring-boot-autoconfigure-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-logging2.3.1.RELEASEspring-boot-starter-logging-2.3.1.RELEASE.jar;D:WorkMaven
epositorychqoslogbacklogback-classic1.2.3logback-classic-1.2.3.jar;D:WorkMaven
epositorychqoslogbacklogback-core1.2.3logback-core-1.2.3.jar;D:WorkMaven
epositoryorgapachelogginglog4jlog4j-to-slf4j2.13.3log4j-to-slf4j-2.13.3.jar;D:WorkMaven
epositoryorgapachelogginglog4jlog4j-api2.13.3log4j-api-2.13.3.jar;D:WorkMaven
epositoryorgslf4jjul-to-slf4j1.7.30jul-to-slf4j-1.7.30.jar;D:WorkMaven
epositoryjakartaannotationjakarta.annotation-api1.3.5jakarta.annotation-api-1.3.5.jar;D:WorkMaven
epositoryorgyamlsnakeyaml1.26snakeyaml-1.26.jar;D:WorkMaven
epositoryorgspringframeworkspring-core5.2.7.RELEASEspring-core-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-jcl5.2.7.RELEASEspring-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:WorkJdkinjava.exe "-javaagent:D:WorkIdeaIntelliJ IDEA 2019.3.4libidea_rt.jar=56290:D:WorkIdeaIntelliJ IDEA 2019.3.4in" -Dfile.encoding=UTF-8 -classpath D:WorkJdkjrelibcharsets.jar;D:WorkJdkjrelibdeploy.jar;D:WorkJdkjrelibextaccess-bridge-64.jar;D:WorkJdkjrelibextcldrdata.jar;D:WorkJdkjrelibextdnsns.jar;D:WorkJdkjrelibextjaccess.jar;D:WorkJdkjrelibextjfxrt.jar;D:WorkJdkjrelibextlocaledata.jar;D:WorkJdkjrelibext
ashorn.jar;D:WorkJdkjrelibextsunec.jar;D:WorkJdkjrelibextsunjce_provider.jar;D:WorkJdkjrelibextsunmscapi.jar;D:WorkJdkjrelibextsunpkcs11.jar;D:WorkJdkjrelibextzipfs.jar;D:WorkJdkjrelibjavaws.jar;D:WorkJdkjrelibjce.jar;D:WorkJdkjrelibjfr.jar;D:WorkJdkjrelibjfxswt.jar;D:WorkJdkjrelibjsse.jar;D:WorkJdkjrelibmanagement-agent.jar;D:WorkJdkjrelibplugin.jar;D:WorkJdkjrelib
esources.jar;D:WorkJdkjrelib
t.jar;D:PersonalJavaProjectio	argetclasses;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-data-jdbc2.3.1.RELEASEspring-boot-starter-data-jdbc-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-jdbc2.3.1.RELEASEspring-boot-starter-jdbc-2.3.1.RELEASE.jar;D:WorkMaven
epositorycomzaxxerHikariCP3.4.5HikariCP-3.4.5.jar;D:WorkMaven
epositoryorgspringframeworkspring-jdbc5.2.7.RELEASEspring-jdbc-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-jdbc2.0.1.RELEASEspring-data-jdbc-2.0.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-relational2.0.1.RELEASEspring-data-relational-2.0.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkdataspring-data-commons2.3.1.RELEASEspring-data-commons-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-tx5.2.7.RELEASEspring-tx-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-context5.2.7.RELEASEspring-context-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-aop5.2.7.RELEASEspring-aop-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-expression5.2.7.RELEASEspring-expression-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-beans5.2.7.RELEASEspring-beans-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgslf4jslf4j-api1.7.30slf4j-api-1.7.30.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter2.3.1.RELEASEspring-boot-starter-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot2.3.1.RELEASEspring-boot-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-autoconfigure2.3.1.RELEASEspring-boot-autoconfigure-2.3.1.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkootspring-boot-starter-logging2.3.1.RELEASEspring-boot-starter-logging-2.3.1.RELEASE.jar;D:WorkMaven
epositorychqoslogbacklogback-classic1.2.3logback-classic-1.2.3.jar;D:WorkMaven
epositorychqoslogbacklogback-core1.2.3logback-core-1.2.3.jar;D:WorkMaven
epositoryorgapachelogginglog4jlog4j-to-slf4j2.13.3log4j-to-slf4j-2.13.3.jar;D:WorkMaven
epositoryorgapachelogginglog4jlog4j-api2.13.3log4j-api-2.13.3.jar;D:WorkMaven
epositoryorgslf4jjul-to-slf4j1.7.30jul-to-slf4j-1.7.30.jar;D:WorkMaven
epositoryjakartaannotationjakarta.annotation-api1.3.5jakarta.annotation-api-1.3.5.jar;D:WorkMaven
epositoryorgyamlsnakeyaml1.26snakeyaml-1.26.jar;D:WorkMaven
epositoryorgspringframeworkspring-core5.2.7.RELEASEspring-core-5.2.7.RELEASE.jar;D:WorkMaven
epositoryorgspringframeworkspring-jcl5.2.7.RELEASEspring-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。