有没有办法从Java中的内存映射文件中获取对象类型

Question

I want to store objects belonging to different classes in a single memory mapped file. While reading from the file is there any approach to know the object type.

Is memory mapped file is used for only single java class?

try {    
    RandomAccessFile memoryMappedFile = new RandomAccessFile(file,mode);    
    long fileSize = memoryMappedFile.length();    
    System.out.println("file size " + fileSize);    
    FileChannel fc = memoryMappedFile.getChannel();    
    System.out.println("Chaannel size" + fc.size());    
    MappedByteBuffer outBuffer = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());    
    List<MemoryMappedFile> list = new ArrayList<MemoryMappedFile>();    
    while(outBuffer.hasRemaining()) {    
        MemoryMappedFile mf = new MemoryMappedFile(outBuffer.getLong(), outBuffer.getInt(), outBuffer.getDouble());        
        list.add(mf);    
    }
    fc.close();
    memoryMappedFile.close();
}

Answer 1

If you make a custom method to serialize your objects you can include starting and ending bytes or a certain format to what you write. Then, knowing how it is written, you can make a method to read files of that specific format. This would, of course, require more work than just using the standard Java serialization library though.