Can Jdk8 static variables be serialized?

Aug 17, 2023120

AI Translation

This post is translated from Chinese into English through AI.View Original

AI-generated summary

In summary, the static variable "remark" in the SysRole class cannot be serialized. When the SysRole object is serialized and then deserialized, the static variable is not included in the deserialized object. This is because static variables are stored in the class object and not in the serialized object.

First of all, static variables cannot be serialized.

Verification:

Entity class:

@Data
public class SysRole implements Serializable {

    // Role ID
    private BigInteger id;
    // Role name
    private String name;
    // Role code to determine if it is a system administrator
    private String code;
    // Role description
    private String description;
    // Creator ID
    private BigInteger createBy;
    // Modifier ID
    private BigInteger modifyBy;
    // Status: 0 - disabled, 1 - enabled
    private int status;
    // Creation time
    private Date created;
    // Last update time
    private Date lastUpdateTime;
    
    private static String remark;
    
    public void setRemark(String remark){
        this.remark = remark;
    }
    
    public String getRemark(){
        return remark;
    }
}

Serialization:

SysRole sysRole = new SysRole();
sysRole.setName("213");
sysRole.setCreated(new Date());
sysRole.setCode("132");
System.out.println(sysRole.toString());
sysRole.setRemark("how");
ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("d:/user.txt"));
objectOutputStream.writeObject(sysRole);

Deserialization:

ObjectInputStream objectInputStream = null;
try {
    objectInputStream = new ObjectInputStream(new FileInputStream("d:/user.txt"));
} catch (IOException e) {
    throw new RuntimeException(e);
}
SysRole readObject = null;
try {
    readObject = (SysRole)objectInputStream.readObject();
} catch (IOException e) {
    throw new RuntimeException(e);
} catch (ClassNotFoundException e) {
    throw new RuntimeException(e);
}
System.out.println(readObject.getRemark());

Result:

Exception
Deserialization code:

---------Added code------------
SysRole sysRole = new SysRole();
sysRole.setRemark("what");
---------Added code------------

ObjectInputStream objectInputStream = null;
try {
    objectInputStream = new ObjectInputStream(new FileInputStream("d:/user.txt"));
} catch (IOException e) {
    throw new RuntimeException(e);
}
SysRole readObject = null;
try {
    readObject = (SysRole)objectInputStream.readObject();
} catch (IOException e) {
    throw new RuntimeException(e);
} catch (ClassNotFoundException e) {
    throw new RuntimeException(e);
}
System.out.println(readObject.getRemark());

Result:

Reason analysis:

In other words, static variables are stored on the class object. Therefore, after sysRole sets the remark, it will be saved on the class object for subsequent use by SysRole objects.