jsp页面用getAttribute()获得的对象是Object()类型的

jsp页面用getAttribute()获得的对象是Object()类型的，若要存放到list或者是arraylist中需要强制转换

ArrayList alBookList=request.getAttribute("bookList");      出现Type mismatch: cannot convert from Object to ArrayList

只需要改为ArrayList alBookList=(ArrayList)request.getAttribute("bookList");