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What does the transient keyword in java do?

王林

Release： 2019-11-26 10:30:28

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What does the transient keyword in java do?

Function:

When serializing data, if you don’t want to serialize one of the attributes into a file, you need to use transient Modification, indicating that the attribute is a temporary attribute

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This is a student class:

public class Student implements Serializable {//注意：要想序列化，必须实现Serializable接口
 
    private String name;
    private Integer age;
    private transient String address;  //使用transient修饰
 
    public Student() {
    }
 
    public Student(String name, Integer age, String address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }
    //Getter/Setter
}

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When I serialize, I don’t plan to save the student’s address attribute. I only want to save the name and age attributes. I modify the adress attribute with the transient keyword and serialize it as follows:

public class TestStudent {
 
    public static void main(String[] args) throws IOException {
 
        List<Student> list = new ArrayList<>();
        Student s1 = new Student("Jack", 20, "北京");
        Student s2 = new Student("Rose", 21, "上海");
        Student s3 = new Student("Hoke", 22, "深圳");
        Student s4 = new Student("Mark", 23, "天津");
        Student s5 = new Student("Json", 24, "成都");
 
        list.add(s1);
        list.add(s2);
        list.add(s3);
        list.add(s4);
        list.add(s5);
 
        //将学生信息序列化到student.txt文件中
        File file = new File("student.txt");
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(file));
        oos.writeObject(list);
 
    }
}

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Proceed below Deserialize and verify the role of transient:

@Test
    public void test() throws IOException, ClassNotFoundException {
 
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(new File("student.txt")));
 
        Object object = ois.readObject();
        if (object instanceof List) {
            List<Student> list = (List<Student>) object;
            list.forEach(System.out::println);
        }
    }

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Result:

What does the transient keyword in java do?

You can see that the address attribute value in the output result is null. The value is not serialized;

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