我錯誤地實現了調用DAO層的方式嗎? DAO方法中不會觸發斷點,並且異常拋出只會提及NullPointerException.Kindly建議。謝謝Java〜服務層無法調用DAO層並拋出NullPointerException
服務層: 公共類BookServiceImpl {
private static BookServiceImpl myInstance;
private BookDAO dao;
public static BookServiceImpl getInstance() {
if (myInstance == null) {
myInstance = new BookServiceImpl();
}
return myInstance;
}
public List<Book> getBookList(BookDTO dto) {
return dao.getBookList(dto);
}
}
DAO層 公共類BookDAO { 私人BookDAO(){ sqlService = Services.get(SqlService.class); }
public static BookDAO getInstance() {
if (myInstance == null) {
myInstance = new BookDAO();
}
return myInstance;
}
}
ya,你是對的......我忘記了......並且不斷思考發生了什麼......哈哈......無論如何..謝謝兄弟... – Chang