IO流必知必会(18)——单例模式类序列化与readResolve()

java中有一个与writeReplace()相对的方法readReasolve()，该方***在readObject之后调用，可以实现保护性的复制整个对象。所有的单例类在实现序列化时，都应该重写readReasolve()方法，这样才能确保在反序列化回来后的对象与单例对象是同一对象(反序列化恢复对象不需要调用构造器)。参考下列代码。

public class School implements Serializable {
    public static School highSchool = new School();
    private School() {
    }
}

public class readResolveTest {
    public static void main(String[] args) throws Exception {
        ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(
                "test.txt"));
        ObjectInputStream ois = new ObjectInputStream(new FileInputStream(
                "test.txt"));
        oos.writeObject(School.highSchool);
        School sch = (School) ois.readObject();
        //false
        System.out.println(sch == School.highSchool);
    }
}

将school中的readResolve重写后，readResolveTest将输出true。

public class School implements Serializable {
    public static School highSchool = new School();

    private School() {
    }

     public Object readResolve() {
     return highSchool;
     }

}