Question

我一直在尝试进行对象序列化，反序列化程序。当我直接在FileInputStream中提供文件名时，我的程序运行得非常好，我能够成功地反序列化对象。但是当我尝试使用FileDialog时，序列化程序运行良好，但无法进行反序列化。我收到以下错误：

java.io.FileNotFoundException: nullnull (The system cannot find the file specified)
at java.io.FileInputStream.open(Native Method)
    at java.io.FileInputStream.<init>(Unknown Source)
    at java.io.FileInputStream.<init>(Unknown Source)
    at package1.Deserialisation.main(Deserialisation.java:22)
Exception in thread "main" java.lang.NullPointerException
    at package1.Deserialisation.main(Deserialisation.java:43) .

任何人都可以帮我解决同样的问题而且还要解释其原因，以免错误再次发生..

以下是我的代码：

       package package1;
        public class Employee implements java.io.Serializable
        {
    private static final long serialVersionUID = 2L;

    String name;
    String address;
    int age;
    //int SSN;
    transient int SSN;    
    public void checkDetails()
    {
        System.out.println("The check details for the employee" + name + "are :");
    }

}

         Serialisation:
         package package1;
        import java.awt.FileDialog;
        import java.awt.Frame;
        import java.io.FileOutputStream;
        import java.io.IOException;
        import java.io.ObjectOutputStream;

        public class Serialization 
         {
     public static void main(String[] args)
     {
          Employee emp =new Employee();
          emp.name="vidhya";
          emp.address="XYZ";
          emp.age=26;
          emp.SSN=123456;
          try 
          {   
            FileDialog fd =new FileDialog(new Frame(),"Save As...",FileDialog.SAVE);

            fd.setVisible(true);
            String filepath=new String (fd.getDirectory()+fd.getFile());
            FileOutputStream fileout =new FileOutputStream(filepath);
    ObjectOutputStream objout=new ObjectOutputStream(fileout);
    objout.writeObject(emp);
    fileout.close();
    objout.close();
    } 
          catch (IOException e2) {
        e2.printStackTrace();
        }
            }
       }


    Deserialisation :
         package package1;
        import java.awt.FileDialog;
        import java.awt.Frame;
        import java.io.FileInputStream;
        import java.io.IOException;
       import java.io.ObjectInputStream;
       public class Deserialisation 
       {
        static Employee emp=null;
    public static void main(String[] args) 
    {
      try {  
        FileDialog fd1 =new FileDialog(new Frame(),"Open...",FileDialog.LOAD);
        String filepath = new String(fd1.getDirectory() + fd1.getFile());
        FileInputStream filein =new FileInputStream(filepath);
        ObjectInputStream objin =new ObjectInputStream(filein);
        emp=(Employee) objin.readObject();
        objin.close();
        filein.close();
        } 

        catch (IOException e) 
        {
        e.printStackTrace();
        } 
        catch (ClassNotFoundException e1)
        {
            System.out.println("Employee class not found");
            e1.printStackTrace();
            return;       
        }

        System.out.println("Employee Name : " + emp.name);
        System.out.println("Address :" + emp.address);
        System.out.println("Age : " + emp.age);
        System.out.println("SSN :" + emp.SSN);
    }

}

Answer 1

String filepath = new String(fd1.getDirectory() + fd1.getFile());

这是创建“nullnull”的路径，这意味着这两个值都为null。尝试在上面一行之前使用fd1.show();。

编辑：正如Viydha所指出的那样，show（）已被弃用，应该使用setVisible（）。

Answer 2

错误发生在FileDialog。这一行：

String filepath = new String (fd.getDirectory()+fd.getFile());

创建nullnull的路径。您应该在此行之前执行fd.show();，或者更好地使用JFileChooser

对象序列化

2 个答案: