java transient 知识点学习

今天看源码的时候看到这个关键字，完全没见过，不懂。好吧！学习一下。

我们都知道实现了Serilizable接口的类，便可以序列化，那么其中某些成员变量不想被序列化怎么办？就是利用transient这个关键字来实现。废话不多说，上例子。

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class TransientTest {
    
    public static void main(String[] args) {
        
        User user = new User();
        user.setUsername("lee");
        user.setPasswd("123456");
        
        System.out.println("read before Serializable: ");
        System.out.println("username: " + user.getUsername());
        System.err.println("password: " + user.getPasswd());
        
        try {
            ObjectOutputStream os = new ObjectOutputStream(
                    new FileOutputStream("C:/f_work/user.txt"));
            os.writeObject(user);
            os.flush();
            os.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        try {
            ObjectInputStream is = new ObjectInputStream(new FileInputStream(
                    "C:/f_work/user.txt"));
            user = (User) is.readObject();
            is.close();
            
            System.out.println("
read after Serializable: ");
            System.out.println("username: " + user.getUsername());
            System.err.println("password: " + user.getPasswd());
            
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}


import java.io.Serializable;

class User implements Serializable {
    private static final long serialVersionUID = 8294180014912103005L;  
    
    private String username;
    private transient String passwd;
    
    public String getUsername() {
        return username;
    }
    
    public void setUsername(String username) {
        this.username = username;
    }
    
    public String getPasswd() {
        return passwd;
    }
    
    public void setPasswd(String passwd) {
        this.passwd = passwd;
    }

}

运行结果:

read before Serializable:
password: 123456
username: lee

read after Serializable:
username: lee
password: null

null说明没有取到信息。