transient 功能: 当对象被序列化时(写入字节序列到目标文件)时,transient阻止实例中那些用此关键字声明的变量持久化;当对象被反序列化时(从源文件读取字节序列进行重构),这样的实例变量值不会被持久化和恢复。
大家请看下面的代码
public class UserTest implements Serializable {
private String name;
private String password;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "UserTest{" +
"name='" + name + '\'' +
", password='" + password + '\'' +
'}';
}
}
public static void main(String[] args) throws IOException, ClassNotFoundException {
UserTest userTest = new UserTest();
userTest.setName("xiaoming");
userTest.setPassword("123456");
System.out.println(userTest.toString());
String relativelyPath=System.getProperty("user.dir");
ObjectOutputStream os = new ObjectOutputStream(
new FileOutputStream(relativelyPath + "/src/main/resources/user.txt"));
//写入文件
os.writeObject(userTest);
os.flush();
os.close();
//读入文件
ObjectInputStream is = new ObjectInputStream(new FileInputStream(
relativelyPath + "/src/main/resources/user.txt"));
//读入文件
userTest = (UserTest) is.readObject();
System.out.println(userTest.toString());
is.close();
}
//输出
UserTest{name='xiaoming', password='123456'}
UserTest{name='xiaoming', password='123456'}
上述是正常的序列化写入文件,然后读取文件的逻辑。
在使用 transient 后:
public class UserTest implements Serializable {
private String name;
//注意这里的 transient
transient private String password;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "UserTest{" +
"name='" + name + '\'' +
", password='" + password + '\'' +
'}';
}
}
然后再运行程序,输出结果如下:
UserTest{name='xiaoming', password='123456'}
UserTest{name='xiaoming', password='null'}
可以看到 password 在被 transient 修饰后,没有序列化和反序列化