复习transient关键字的使用

一句话概括：对于某些数据，如果你不想serialize，那么就让之transient，最简单的例子——password，代码如下：

class LoggingInfo implements java.io.Serializable   
{   
    private Date loggingDate = new Date();   
    private String uid;   
    private transient String pwd;  
      
    LoggingInfo(String user, String password)   
    {   
        uid = user;   
        pwd = password;   
    }   
    public String toString()   
    {   
        String password=null;   
        if(pwd == null)   
        {   
        password = "NOT SET";   
        }   
        else  
        {   
            password = pwd;   
        }   
        return "logon info: \n   " + "user: " + uid +   
            "\n   logging date : " + loggingDate.toString() +   
            "\n   password: " + password;   
    }
    
}  

class GuestLoggingInfo extends LoggingInfo {
    
    public GuestLoggingInfo() {
        super("guest", "guest");
    }
    public GuestLoggingInfo(String user, String password) {
        super(user, password);
    }
}

public class Foo {
    
    public static void main(String[] args) {
        LoggingInfo logInfo = new LoggingInfo("MIKE", "MECHANICS");   
        System.out.println(logInfo.toString());   
        try  
        {   
           ObjectOutputStream o = new ObjectOutputStream(   
                        new FileOutputStream("e:/logInfo.out"));   
           o.writeObject(logInfo);   
           o.close();   
        }   
        catch(Exception e) {
            //deal with exception
        }   
          
        try  
        {   
           ObjectInputStream in =new ObjectInputStream(   
                        new FileInputStream("e:/logInfo.out"));   
           LoggingInfo logInfo2 = (LoggingInfo)in.readObject();   
           System.out.println(logInfo2.toString());   
        }   
        catch(Exception e) {
            //deal with exception
        }
        
        System.out.println("---------------------");
        
        GuestLoggingInfo guestLoggingInfo = new GuestLoggingInfo();
        System.out.println(guestLoggingInfo);
        try {
            ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("e:/logInfo.out"));
            objectOutputStream.writeObject(guestLoggingInfo);
            objectOutputStream.close();
        } catch (Exception e) {
            // TODO: handle exception
        }
        try {
            ObjectInputStream objectInputStream = new ObjectInputStream(new FileInputStream("e:/logInfo.out"));
            guestLoggingInfo = (GuestLoggingInfo)objectInputStream.readObject();
            objectInputStream.close();
        } catch (Exception e) {
            // TODO: handle exception
        }
        System.out.println(guestLoggingInfo); // constructor并没有被调用
    }
}