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@zhanggang807
Created March 22, 2018 01:52
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java Externalizable interface demo
import java.io.*;
/**
* reference link
* https://mp.weixin.qq.com/s/QS9e_lVxr5vuphql5O3xhA
* https://www.cnblogs.com/chenfei0801/archive/2013/04/06/3002146.html
* 对一个实现了Externalizable接口的类进行序列化及反序列化
*/
public class ExternalizableDemo1 {
public static void main(String[] args) {
//Write Obj to file
User1 user = new User1();
user.setName("hollis");
user.setAge(23);
try (ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("tempFile"))) {
oos.writeObject(user);
} catch (IOException e) {
e.printStackTrace();
}
//Read Obj from file
File file = new File("tempFile");
try (ObjectInputStream ois = new ObjectInputStream(new FileInputStream(file))) {
User1 newInstance = (User1) ois.readObject();
//output
System.out.println(newInstance);
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
}
}
}
//OutPut:
//User{name='null', age=0}
//在writeExternal readExternal 写入相关代码后发现有值了
//我觉得write 和 read 必须按顺序来,什么顺序write 就什么顺序 read
//Externalizable这个可以控制某些字段序列化时不输入值,或者某些字段可以输出值,也可以使用 transient 关键字来实现
//Externalizable 相比 Serializable接口更加的可控,更加的灵活
class User1 implements Externalizable {
private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public void writeExternal(ObjectOutput out) throws IOException {
System.out.println("invoke writeExtenal???");
out.writeObject(name);//原本是不输入值的,加了这个之后读时就会读出来,
out.writeInt(age);
}
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
System.out.println("invoke readExtenal???");
name = (String) in.readObject();// 原本是不输出值的,现在有值了
age = in.readInt();
}
public User1() {
}
@Override
public String toString() {
return "User{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
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