无法从 Java 中的二进制文件中读取对象

Question

我正在尝试将序列化数据从 .dat 文件读取到相应的 java class 文件中。我的 .readObject() 方法不断抛出 ClassNotFoundException。为什么它不能从文件中读取数据？我正在尝试将它读给一个学生 class，他的构造函数接受其类型的对象，然后将该对象的变量的值分配给它的变量。

public class StudentTest 
{
    private static ObjectInputStream OIS;
    public static void main(String[] args)
    {

        openFile();
        readFile();
        closeFile();
    }

    public static void openFile()
    {
        try
        {
            OIS=new ObjectInputStream(Files.newInputStream(Paths.get("C:\Users\Joey\Desktop\students.dat")));
        }
        catch(IOException e)
        {
            System.out.println("Error trying to read file. TERMINATING.");
            System.exit(1);
        }
    }

    public static void readFile()
    {
        try
        {
            while(true)
            {
                Student student=new Student((Student)OIS.readObject());
                System.out.printf("%s", student.toString());
            }
        }
        catch(ClassNotFoundException e)
        {
            System.out.println("Class not found. Terminating.");
            System.exit(1);
        }
        catch(EOFException e)
        {
            System.out.println("End of file reached.");
        }
        catch(IOException e)
        {
            System.out.println("Error reading from file. TERMINATING.");
            System.exit(1);
        }
    }

    public static void closeFile()
    {
        try
        {
            if(OIS!=null)
                OIS.close();
        }
        catch(IOException e)
        {
            System.out.println("IOEXCEPTION.");
            System.exit(1);
        }
    }
}

这是堆栈跟踪：

java.lang.ClassNotFoundException: files.Student
at java.net.URLClassLoader.run(Unknown Source)
at java.net.URLClassLoader.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Unknown Source)
at java.io.ObjectInputStream.resolveClass(Unknown Source)
at java.io.ObjectInputStream.readNonProxyDesc(Unknown Source)
at java.io.ObjectInputStream.readClassDesc(Unknown Source)
at java.io.ObjectInputStream.readOrdinaryObject(Unknown Source)
at java.io.ObjectInputStream.readObject0(Unknown Source)
at java.io.ObjectInputStream.readObject(Unknown Source)
at studentfiles.StudentTest.readFile(StudentTest.java:40)
at studentfiles.StudentTest.main(StudentTest.java:16)

Answer 1

您的 Student class 与预期的包裹不同。如果您打印 ClassNotFoundException 附带的异常消息，您将看到预期的包是什么。

并且创建 ObjectInputStream 或 FileInputStream 的错误不一定是 'error reading from file'。不要自己编造错误信息。使用异常附带的那个。即使您有正确的消息，如 ClassNotFoundException，您也遗漏了未找到的实际 class 名称，该名称位于异常消息中。不要这样做。

无法从 Java 中的二进制文件中读取对象

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