验证transient关键字

对对象进行序列化时，有些实例域是不需要序列化的，可以在该实例域前加transient关键字
public class LoggingInfo implements java.io.Serializable{
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        LoggingInfo logInfo = new LoggingInfo("MIKE", "MECHANICS");
        System.out.println(logInfo.toString());
        try {
            ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream("logInfo"));
            o.writeObject(logInfo);//将对象状态写入输出流
            o.close();
        } catch (Exception e) {// deal with exception

        }

        // To read the object back, we can write
        try {
            ObjectInputStream in = new ObjectInputStream(new FileInputStream("logInfo"));
            LoggingInfo logInfo1 = (LoggingInfo) in.readObject();//从输入流读取对象状态
            System.out.println(logInfo1.toString());
        } catch (Exception e) {// deal with exception

        }
    }
    private static final long serialVersionUID = 1L;
    private Date loggingDate = new Date();
    private String uid;
    private transient String pwd;//不序列化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;
    }
}
运行上面的测试类，输出：
logon info:
   user: MIKE
   logging date : Tue Jul 20 15:37:20 CST 2010
   password: MECHANICS                --------------->初始状态正常获取对象的状态值
logon info:
   user: MIKE
   logging date : Tue Jul 20 15:37:20 CST 2010
   password: NOT SET                      ------------->不能得到对象的状态值，表明pwd未被序列化

 

总结：通过以上测试可以得知，给实例域加上transient关键字后，序列化该对象时相应的实例域不会被序列化