java - 反序列化时出现异常

Question

我正在尝试反序列化一个实现可序列化接口(interface)的类并扩展不可序列化的类。

/**
* 
*/
package com.test;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;


public class SerializationTest  implements Serializable {

/**
 * 
 */
private static final long serialVersionUID = -1324438308227634614L;

class Papa{
    Papa(){
        System.out.println("Papa called..");
    }
}
class Student extends Papa implements Serializable{

    /**
     * 
     */
    private static final long serialVersionUID = 8667392485783922740L;

    String name;
    int id;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    /**
     * 
     */
    public Student() {
        System.out.println("Constructor called");
    }

}

public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException {
    Student arvind = new SerializationTest().new Student();
    arvind.setName("Arvind");
    arvind.setId(123);

    serialize(arvind);
    System.out.println("Serialization done..");
    deserialize();
}

/**
 * @throws IOException 
 * @throws FileNotFoundException 
 * @throws ClassNotFoundException 
 * 
 */
private static void deserialize() throws FileNotFoundException, IOException, ClassNotFoundException {

    ObjectInputStream ois = new ObjectInputStream(new FileInputStream("tests.txt"));

    Student arvind = (Student)ois.readObject();
    System.out.println("Deserialize name - " + arvind.getName());
    System.out.println(arvind.getId());
    ois.close();

}

/**
 * @param arvind
 * @throws IOException
 * @throws FileNotFoundException
 */
private static void serialize(Student arvind) throws IOException, FileNotFoundException {
    ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("tests.txt"));

    oos.writeObject(arvind);
    oos.flush();
    oos.close();
}
}

我收到以下异常 -

Exception in thread "main" java.io.InvalidClassException: com.test.SerializationTest$Student; no valid constructor
at java.io.ObjectStreamClass$ExceptionInfo.newInvalidClassException(Unknown Source)
at java.io.ObjectStreamClass.checkDeserialize(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at com.test.SerializationTest.desseialize(SerializationTest.java:88)
at com.test.SerializationTest.main(SerializationTest.java:75)

我已经关注了java.io.InvalidClassException: no valid constructor的回答通过创建默认构造函数，但它也没有帮助。

非常感谢任何建议和帮助。

Answer 1

您所需要的只是将 Student 和 Papa 公共(public)类放在单独的文件中，或者像这样将它们设置为静态。

static class Papa{
    Papa(){
        System.out.println("Papa called..");
    }
}
static class Student extends Papa implements Serializable{

    /**
     *
     */
    private static final long serialVersionUID = 8667392485783922740L;

    String name;
    int id;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    /**
     *
     */
    public Student() {
        System.out.println("Constructor called");
    }

}

您的代码不起作用的原因是内部 Papa 类的构造函数无法在 Student 类的构造函数中直接调用。我们将 Papa 设为静态以摆脱这种束缚。