HTTP状态500：org.apache.jasper.JasperException：java.lang.NullPointerException

Question

有我的jsp代码：

<%if (session.getAttribute("login") == null) {%>
                    <div id="login">
                        <div class="loginContent">
                            <form action="connexion" method="POST" id="login_frm">
                                <label ><b>Username: </b></label>
                                <input class="field" type="text" id="log" name="login" value="" size="23" />
                                <label ><b>Password:</b></label>
                                <input class="field" type="password"  id="pwd" size="23" />
                                <input type="submit"  value="" class="button_login" />
                            </form>
                       <div class="left">
                           <label for="rememberme"><input name="rememberme" id="rememberme" class="rememberme" type="checkbox" checked="checked" value="forever" /> Remember me</label></div>
                            <div class="right">Not a member? <a href="#">Register</a> | <a href="#">Lost your password?</a></div>
                      </div>
                      <div class="loginClose"><a href="#" id="closeLogin" onclick="closeForm()">Fermer panneau</a></div>
                    </div>
                 <% } else {%>
                 <h3><a href="Deconnecte">Déconnexion</a><br></h3>
                 <h3> Bonjour: <%= session.getAttribute("login")%></h3>
                 <%}%>

还有我的servlet：

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    String login = request.getParameter("login")
    HttpSession session = request.getSession();
    session.setAttribute("login", login);
    System.out.println(session.getAttribute("login"));     getServletConfig().getServletContext().getRequestDispatcher("/recommandation.jsp").forward(request, response);
}

当我单击登录按钮后，出现错误。

INFO: appachito ATTENTION: ApplicationDispatcher[/RecommandationDefault] PWC1231: Servlet.service() for servlet jsp threw exception java.lang.NullPointerException at org.apache.jsp.recommandation_jsp._jspService(recommandation_jsp.java from :300) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:109) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:406) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:483) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:373) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523) at org.apache.catalina.core.ApplicationDispatcher.doInvoke(ApplicationDispatcher.java:822) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:517) at org.apache.catalina.core.ApplicationDispatcher.doDispatch(ApplicationDispatcher.java:488) at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:379) at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:336) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:314) at package1.connexion.doPost(connexion.java:47) at javax.servlet.http.HttpServlet.service(HttpServlet.java:754) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641) at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97) at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185) at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57) at com.sun.grizzly.ContextTask.run(ContextTask.java:69) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309) at java.lang.Thread.run(Thread.java:619)

ATTENTION: StandardWrapperValve[connexion]: PWC1406: Servlet.service() for servlet connexion threw exception java.lang.NullPointerException at org.apache.jsp.recommandation_jsp._jspService(recommandation_jsp.java from :300) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:109) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:406) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:483) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:373) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523) at org.apache.catalina.core.ApplicationDispatcher.doInvoke(ApplicationDispatcher.java:822) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684) at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:517) at org.apache.catalina.core.ApplicationDispatcher.doDispatch(ApplicationDispatcher.java:488) at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:379) at org.apache.catalina.core.ApplicationDispatcher.dispatch(ApplicationDispatcher.java:336) at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:314) at package1.connexion.doPost(connexion.java:47) at javax.servlet.http.HttpServlet.service(HttpServlet.java:754) at javax.servlet.http.HttpServlet.service(HttpServlet.java:847) at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1523) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:279) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:188) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:641) at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:97) at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:85) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:185) at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:325) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:226) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:165) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:791) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:693) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:954) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:170) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:135) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:102) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:88) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:76) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:53) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:57) at com.sun.grizzly.ContextTask.run(ContextTask.java:69) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:330) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:309) at java.lang.Thread.run(Thread.java:619)

提前致谢

Answer 1

在Tomcat中，将为应用程序中的每个jsp文件创建一个.java和.class文件，并且可以从以下路径找到相同的文件： Apache-Tomcat\\work\\Catalina\\localhost\\'ApplicationName'\\org\\apache\\jsp\\index_jsp.java

在您的情况下，jsp名称是recommandation.jsp，因此路径应类似于您尝试访问的第300行中的Apache-Tomcat\\work\\Catalina\\localhost\\'ApplicationName'\\org\\apache\\jsp\\recommandation_jsp.java 。一个空对象，导致空指针异常。

如果您使用的是Glassfish ，则可以在your-domain-dir/generated/jsp/j2ee-modules\\\\YourModule/org/apache/jsp找到已编译的jsp文件。

在我的系统上，它是C:\\glassfish-4.0\\glassfish\\domains\\domain1\\generated\\jsp\\WebApplication1\\org\\apache\\jsp