Question

我正在努力解决这个错误并且无法解决错误：

我的班级：

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)

任何帮助？

提前致谢：）

Answer 1

你遇到过使用Java序列化的一个陷阱是持久性框架（而不是用于通信的数据格式）。您保留了学生数据，然后更改了学生课程。现在，当您尝试读取持久化数据时，它会失败，因为基本上，该类的两个版本不匹配。如果您在学生班级上手动指定了serialVersionUID，则序列化框架在读取数据文件时不会被阻塞（无论如何都不会立即）。

但根本问题是序列化与持久性不同 - 如果要保存学生数据，则需要选择一个框架，这样做不容易受到类文件不兼容的影响。我建议保存为CSV文件以启动，如果项目复杂性需要，也可以查看数据库解决方案。

*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内容。这不是一个很好的修复，它取决于自创建文件以来类已经改变了多少：

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

    // ...
}

由于项目要求使用对象输出流，我建议在Externalizable类上实现Student接口，并实现读取/写入对象输出流的方法：

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
   }

   // ...
}

Answer 2

取自Javadoc：

http://java.sun.com/j2se/1.4.2/docs/api/

公共类InvalidClassException 扩展ObjectStreamException

序列化运行时检测到以下问题之一时抛出与班级。

该类的序列版本与该类的序列版本不匹配从流中读取的描述符
该类包含未知数据类型
该类没有可访问的no-arg构造函数

错误：java.io.InvalidClassException

2 个答案: