一直报空指针异常，代码查不出来什么问题

Question

一直都报错，不知道什么缘故

类型 异常报告

描述 服务器遇到一个意外的情况，阻止它完成请求。

例外情况

java.lang.NullPointerException
cn.edu.hzvtc.servlet.AdminUserAddServlet.doGet(AdminUserAddServlet.java:47)
cn.edu.hzvtc.servlet.AdminUserAddServlet.doPost(AdminUserAddServlet.java:26)

47行： if (result==-1){

26行： this.doGet(request, response);

@WebServlet(name = "AdminUserAddServlet", urlPatterns = "/admin/user_add")
public class AdminUserAddServlet extends HttpServlet {
    private UserService userService = new UserServiceImpl();

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置request字符集
        request.setCharacterEncoding("utf-8");

        //获取请求中的参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String name = request.getParameter("name");
        String email = request.getParameter("email");
        String phone = request.getParameter("phone");
        String address = request.getParameter("address");
        Boolean isadmin = request.getParameter("isadmin") == null ? false : true;
        Boolean isvalidate = request.getParameter("isvalidate") == null ? false : true;

        User user = new User(username, password, name, email, phone, address, isadmin, isvalidate);

        Integer result = userService.addUser(user);
        if (result==-1){
            request.setAttribute("failMsg", "用户名已存在！！！");
            request.setAttribute("user", user);
            request.getRequestDispatcher("/admin/add_user").forward(request, response);
        }else if (result>0){
            request.setAttribute("mas", "用户名新增成功！！！");
            request.getRequestDispatcher("/admin/list_user").forward(request, response);
        }else {
            request.setAttribute("failMsg", "用户名新增失败，请重试！！！");
            request.setAttribute("user", user);
            request.getRequestDispatcher("/admin/add_user").forward(request, response);
        }
    }
}

Answer 1

你可以把 result 打印出来看看，应该是空的，看看你的addUser方法返回的是啥。