HTTP Status 500 – Internal Server Error

想问怎么解决

HTTP Status 500 – Internal Server Error
Type 异常报告

消息 在 [78] 行处理 [/pages/stuList.jsp] 时发生异常

描述 服务器遇到一个意外的情况，阻止它完成请求。

Exception

org.apache.jasper.JasperException: 在 [78] 行处理 [/pages/stuList.jsp] 时发生异常

75: StudentService stuService = new StudentServiceimp();
76: GradeService gradeService = new GradeServiceimp();
77: Grade grade = new Grade();
78: List list = stuService.getAllStudent();
79: session.setAttribute("list", list);
80:
81: %>

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:625)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:514)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
cn.filter.LoginFillter.doFilter(LoginFillter.java:37)
cn.filter.CharEncodingFilter.doFilter(CharEncodingFilter.java:33)
Root Cause

java.lang.NullPointerException
cn.dao.impl.StudentDaoimp.getAllStudent(StudentDaoimp.java:28)
cn.service.impl.StudentServiceimp.getAllStudent(StudentServiceimp.java:26)
org.apache.jsp.pages.stuList_jsp._jspService(stuList_jsp.java:200)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
cn.filter.LoginFillter.doFilter(LoginFillter.java:37)
cn.filter.CharEncodingFilter.doFilter(CharEncodingFilter.java:33)

图片说明

吧这段报异常的代码用try catch包起来抓异常啊

java.lang.NullPointerException
cn.dao.impl.StudentDaoimp.getAllStudent(StudentDaoimp.java:28)

空指针异常，看看连接的数据库表是不是没有数据，查询list为空导致如下异常

session.setAttribute("list", list);

出现问题很正常
解决问题重要的是确认问题，确认问题，大概可以这样。
1、看控制台错误信息，看是否能确认具体哪一行。这个问题明显在StudentDaoimp 28行报了一个空指针错误
2、调试错误处，看为何获取的数据为空。