Question

我打算做一个简单的登录，根据用户的情况向您显示附加给您的账单。。。如果一个企业的成员正在尝试，我只需用equals验证他/她（“admin”，“jefearea”，“almacenero”）。。。问题是，当我成功登录非商业用户时，我得到了各自的账单，但当我点击“查看”按钮时，它给了我一个错误，这是我的页面

JSP form

按下任何“查看”按钮后出现以下错误，即使我只是将其输出.println（“点击”）

HTTP Status 500 - Internal Server Error

这是我的日志

Advertencia:   StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
    at org.apache.jsp.PaginaUsuario_jsp._jspService(PaginaUsuario_jsp.java:85)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:416)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:283)
    at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
    at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
    at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
    at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
    at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:283)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:200)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:132)
    at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:111)
    at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
    at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:536)
    at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
    at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:591)
    at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:571)
    at java.lang.Thread.run(Thread.java:745)

这是我的代码

<body>
        <%
            Entrada_DAO objDAO = null;
            ArrayList<BoletaBean> listabBOL = null;
        %>
        <form name="form1">
            <table>
                <tr>
                    <th>Boleta N°</th>
                    <th>Fecha</th>
                    <th>Estado</th>
                    <th>Total</th>
                    <th></th>
                </tr>
                <tr>
            <%
                String usu = request.getParameter("txtUsu");
                String pas = request.getParameter("txtPas");

                objDAO = new Entrada_DAO();
                int estado = objDAO.GetSesionUsu(usu, pas);

                if(usu.equalsIgnoreCase("admin") && pas.equalsIgnoreCase("admin"))
                {
                    response.sendRedirect("Administrador.jsp");
                }
                else if(usu.equalsIgnoreCase("jefearea") && pas.equalsIgnoreCase("jefearea"))
                {
                    response.sendRedirect("JefeDeArea.jsp");
                }
                else if(usu.equalsIgnoreCase("almacenero") && pas.equalsIgnoreCase("almacenero"))
                {
                    response.sendRedirect("Almacenero.jsp");
                }
                else
                {
                    if(estado == 0)
                    {
                        response.sendRedirect("EntradaSistema.jsp");
                        out.println("Credenciales incorrectas");
                    }
                    else if(estado == 1)
                    {
                        int codigo = 0;
                        codigo = objDAO.GetCodigoSocio(usu);
                        listabBOL = objDAO.DetalleBol(codigo);%>
                        <%
                            try
                            {
                                for (BoletaBean objOCBEAN: listabBOL)
                                {%>  
                                    <td> <%=objOCBEAN.getCodigoBOL()%> </td> 
                                    <td> <%=objOCBEAN.getFecha()%> </td>  
                                    <td> <%=objOCBEAN.getEstado()%> </td>
                                    <td> <%=objOCBEAN.getMonto()%> </td>
                                    <td> <input type="submit" name="btnHola" value="View"> </td>
                            </tr>
                                <%}
                            }
                            catch(Exception exc)
                            {
                                System.out.println("Error: ");
                                System.out.println(exc.toString());
                            }
                     }
                    if(request.getParameter("btnHola") != null)
                    {
                        out.println("Clicked");
                    }
                }%>
            </table>
        </form>
    </body>

我已经阅读了主题“什么是NullPointerException，以及如何修复它？”，并尝试自行修复它，但失败了，我会帮助我知道错误。

Answer 1

很难说NPE来自哪里因为你没有提供代码。

但是我通常会做的事情（因为它很难调试jsp）只是把out.println("step xxx");放在这里和那里看看成功传递了哪些jsp行。您还可以输出一些您怀疑的变量

out.println(usu);

每个按钮都有java.lang.NullPointerException

1 个答案: