调试，测试并调整修改了代码及结构

src/com/chinasofti/dao/BookCopyDAO.java

@@ -1,12 +0,0 @@
-package com.chinasofti.dao;
-
-import com.chinasofti.model.BookCopy;
-import java.util.List;
-
-public interface BookCopyDAO {
-    List<BookCopy> selectByBookId(Long bookId);
-    BookCopy selectAvailableByBookId(Long bookId); // 获取一个可借副本
-    int updateStatus(Long copyId, String status);
-    int insert(BookCopy copy);
-    int countAvailableByBookId(Long bookId);
-}