Question

student.jsp页面获取登陆界面的id,student.jsp采用分页显示，分页代码没问题，点击下一页时，程序报错

严重: Servlet.service() for servlet [jsp] in context with path [/gwork] threw exception [An exception occurred processing JSP page /student.jsp at line 55

52: %>
53: <tr>
54: <td>学号:</td>
55: <td><input type="text" name="id" readOnly style="width:40px" value="<%=s.getId() %>"></td>
56: </tr>
57: <tr>
58: <td>姓名:</td>

Stacktrace:] with root cause
java.lang.NullPointerException
at org.apache.jsp.student_jsp._jspService(student_jsp.java:141)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:987)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:309)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)

Answer 1

登录界面的Student的ID应该放在SESSION里面，然后取出来。。。你的估计应该是在request里面，二次请求后就会出现空指向

Answer 2

空指针~ 你检查下 s是不是出问题了。

55: <td><input type="text" name="id" readOnly style="width:40px" value="<%=s.getId() %>"></td>

Answer 3

上下文路径异常，是不是你的路径写错了