java关键字Transient

transient是Java语言的关键字，用来表示一个域不是该对象串行化的一部分。当一个对象被串行化的时候，transient型变量的值不包括在串行化的表示中，然而非transient型的变量是被包括进去的。private transient String pwd;现在我们创建一个这个类的实例，并且串行化(serialize)它 ,然后将这个串行化对象写入磁盘。LoggingInfo logInfo = new LoggingInfo("MIKE", "MECHANICS");现在，如果我们串行化GuestLoggingInfo的一个实例，将它写入磁盘，并且再将它从磁盘中读出，我们仍然看到读回的对象打印password 为 "NOT SET"。

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import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Date;

public class LoggingInfo implements java.io.Serializable {

private static final long serialVersionUID = 1L;
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;
}

public static void main(String[] args) {

LoggingInfo logInfo = new LoggingInfo("MIKE", "MECHANICS");
System.out.println(logInfo.toString());
try {
ObjectOutputStream o = new ObjectOutputStream(new FileOutputStream(
"logInfo.out"));
o.writeObject(logInfo);
o.close();
} catch (Exception e) {// deal with exception

}

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

}
}
}