java - : java. io.InvalidClassException 中出现错误

Question

我正在解决这个问题，但收到此错误无法指出错误:

这是我的课:

package stdaccmdmngmt;

import java.io.File;
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;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;
import javax.swing.JOptionPane;

/**
 *
 * @author princess
 */
public class Student1 implements Serializable {

public static Set<Student1> listOfStudents = new HashSet<Student1>();    
public static File outFile = new File("StudentRegistry.dat"); 

// Data memebers 
private String studentID;
private String name;
private Date dateOfReg;

//Constructor 
Student1(String number,String name)
{
this.studentID = number;
this.name = name;
dateOfReg = new Date(); 
}


public String getName()
{
return name;
}

public String getStudentID()
{
return studentID;
}

public Date getDateOfReg()
{
return dateOfReg;
}

public void register() throws FileNotFoundException, IOException, ClassNotFoundException    
{ 
Set<Student1> sss = new HashSet<Student1>();    
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(outFile));
oos.writeObject(sss);
oos.close();      
}

public static HashSet<Student> getListOfStudents() throws FileNotFoundException, IOException, ClassNotFoundException
{
HashSet ss;
File inFile = new File("StudentRegistry.dat");
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(inFile));
Set<Student> aNewSet = (HashSet<Student>) ois.readObject();
return  (HashSet<Student>) aNewSet;
}

public static Student getStudentbyID(String a) throws FileNotFoundException, IOException, ClassNotFoundException
{
Set<Student> aNewSet = new HashSet<Student>();
aNewSet = Student.getListOfStudents();
Student result = null;

for (Student x :aNewSet)
{
        if (x.getStudentID().equalsIgnoreCase(a))
        {
             result = x;
             break;
        }
    }  
    if (result == null)
    {
        JOptionPane.showMessageDialog(null, "Apartment not found");
    }
    return result;    

}

    @Override
public String toString()
{
// include the code to retrieve assigned apartment    
return "Name: " + name +" StudentID: "+ studentID + " Registered On: " + dateOfReg;
}


    @Override
public boolean equals(Object another)
{
Student1 stud = (Student1)another;
return this.name.equals(stud.name)&& this.studentID.equals(stud.studentID);
}

    @Override
public int hashCode()
{
int hash = name.hashCode();
return hash;

}    
}

这是测试类:

package stdaccmdmngmt;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author princess
 */
public class Test {

public static void main (String[]args) throws FileNotFoundException, ClassNotFoundException, IOException
{        
Student1 s = new Student1("12345","Sasha");   
        try {
            s.register();
        } catch (FileNotFoundException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex);
        }

Set<Student> nnn;
 nnn = Student.getListOfStudents();
for (Student x : nnn)

    System.out.println(x.toString());      

}

}
 * @author princess
 */
public class Student1 implements Serializable {

public static Set<Student1> listOfStudents = new HashSet<Student1>();    
public static File outFile = new File("StudentRegistry.dat"); 

// Data memebers 
private String studentID;
private String name;
private Date dateOfReg;

//Constructor 
Student1(String number,String name)
{
this.studentID = number;
this.name = name;
dateOfReg = new Date(); 
}


public String getName()
{
return name;
}

public String getStudentID()
{
return studentID;
}

public Date getDateOfReg()
{
return dateOfReg;
}

public void register() throws FileNotFoundException, IOException, ClassNotFoundException    
{ 
Set<Student1> sss = new HashSet<Student1>();    
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream(outFile));
oos.writeObject(sss);
oos.close();      
}

public static HashSet<Student> getListOfStudents() throws FileNotFoundException, IOException, ClassNotFoundException
{
HashSet ss;
File inFile = new File("StudentRegistry.dat");
ObjectInputStream ois = new ObjectInputStream(new FileInputStream(inFile));
Set<Student> aNewSet = (HashSet<Student>) ois.readObject();
return  (HashSet<Student>) aNewSet;
}

public static Student getStudentbyID(String a) throws FileNotFoundException, IOException, ClassNotFoundException
{
Set<Student> aNewSet = new HashSet<Student>();
aNewSet = Student.getListOfStudents();
Student result = null;

for (Student x :aNewSet)
{
        if (x.getStudentID().equalsIgnoreCase(a))
        {
             result = x;
             break;
        }
    }  
    if (result == null)
    {
        JOptionPane.showMessageDialog(null, "Apartment not found");
    }
    return result;    

}

    @Override
public String toString()
{
// include the code to retrieve assigned apartment    
return "Name: " + name +" StudentID: "+ studentID + " Registered On: " + dateOfReg;
}


    @Override
public boolean equals(Object another)
{
Student1 stud = (Student1)another;
return this.name.equals(stud.name)&& this.studentID.equals(stud.studentID);
}

    @Override
public int hashCode()
{
int hash = name.hashCode();
return hash;

}    
}

......................

我收到此错误:

run:
Exception in thread "main" java.io.InvalidClassException: stdaccmdmngmt.Student; local class incompatible: stream classdesc serialVersionUID = -3040096452457271695, local class serialVersionUID = -4849175799723926283
    at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:562)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1732)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
    at java.util.HashSet.readObject(HashSet.java:291)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:974)
    at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1849)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
    at stdaccmdmngmt.Student.getListOfStudents(Student.java:76)
    at stdaccmdmngmt.Test.main(Test.java:34)
Java Result: 1
BUILD SUCCESSFUL (total time: 3 seconds)

有什么帮助吗？

提前致谢:)

Answer 1

使用 Java 序列化的陷阱之一是持久性框架(而不是用于通信的数据格式)。您保留了学生数据，然后更改了学生类(class)。现在，当您尝试读取持久数据时，它会失败，因为基本上，该类的两个版本不匹配。如果您在学生类上手动指定了 serialVersionUID，则序列化框架不会在读取数据文件时卡住(无论如何不会立即卡住)。

但根本问题是序列化与持久性不同 - 如果您想保存学生数据，那么您需要选择一个不易受到类文件不兼容影响的框架。我建议先保存为 CSV 文件，如果项目复杂性允许的话，也可以看看数据库解决方案。

<小时/>

* 编辑*

作为临时修复，您可以尝试将类重命名为 Student 并将 serialVersionUID 设置为序列化框架所期望的值。这不是一个可靠的修复，它取决于自您创建文件以来类发生了多少变化:

public class Student implements Serializable {
    public static final long serialVersionUID = -3040096452457271695L;

    // ...
}

由于您的项目要求使用对象输出流，因此我建议在您的 Student 类上实现 Externalizable 接口(interface)，并实现读/写方法它到一个对象输出流:

public class Student implements Serializable, Externalizable {
    public static final long serialVersionUID = -3040096452457271695L;
    // ...

   @Override
   public void writeExternal(ObjectOutput out) throws IOException {
      out.writeUTF(getStudentID());
      out.writeUTF(getName());
      // etc
   }

   @Override
   public void readExternal(ObjectInput in) throws IOException,
         ClassNotFoundException {
      setStudentID(in.readUTF());
      setName(in.readUTF());
      // etc
   }

   // ...
}