从servlet向jsp发送arraylist时显示错误

Question

ArrayList<Customer> al = new ArrayList<Customer>();
al = abs.viewCustomerReqRequest();
//Return type of viewCustomerReqRequest() method is ArrayList<Customer>

request.setAttribute("Customer_AL",al);
RequestDispatcher rd = request.getRequestDispatcher("a_reg_request.jsp");
rd.forward(request, response);

<%
  ArrayList<Customer> al = new ArrayList<Customer>();
  al = (ArrayList<Customer>) request.getAttribute("Customer_AL");
  Iterator<Customer> it = al.iterator();
%>

Answer 1

ServletRequest.SetAttribute()的第二个参数属于Object类型。

一旦您将list作为object参数传递，它就会丢失编译时类型。警告告诉你这一点。但这是一个警告，而不是一个错误。

如果要取消显示警告，可以使用

@SuppressWarnings("unchecked")
al = (ArrayList<Customer>) request.getAttribute("Customer_AL");