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("\nread 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。