上获得
我在1 Servlet中具有以下代码:
dispatcher = request.getRequestDispatcher("LoginModel");
dispatcher.include(request, response);
if ((boolean) request.getAttribute("Successful")) {}
和第二个servlet:
request.setAttribute("Successful", true);
但是,我一直在request.getAttribute("Successful")
NullPointerException
您的代码这样做的唯一原因是因为您的LoginModel
Servlet没有被调用(顺便说一句,您是否调试了它要检查?)。
NullPointerException
之所以发生,是因为您正在尝试将null引用到boolean
(安全检查可以解决此问题,而不是呼叫本身)。
请参见一个示例,该示例正常工作:
servlet 1:
@WebServlet(urlPatterns = "/serv")
public class Serv extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
RequestDispatcher dispatcher = request.getRequestDispatcher("serv2");
dispatcher.include(request, response);
if (request.getAttribute("Successful") != null
&& (boolean) request.getAttribute("Successful")) {
System.out.println("Success!");
} else {
System.out.println("No success!");
}
}
}
servlet 2:
@WebServlet(urlPatterns = "/serv2")
public class Serv2 extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setAttribute("Successful", true);
}
}
最终结果:
Success!