HTTP Status 500 -

题目

HTTP Status 500 -
type Exception report
message
descriptionThe server encountered an internal error () that prevented it from fulfilling this request.
exceptionjava.lang.NullPointerException
com.ascent.dao.LoginDAO.login(LoginDAO.java:27)
com.ascent.servlet.LoginServlet.Userlogin(LoginServlet.java:73)
com.ascent.servlet.LoginServlet.doGet(LoginServlet.java:42)
com.ascent.servlet.LoginServlet.doPost(LoginServlet.java:31)
javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
com.ascent.util.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:33)
noteThe full stack trace of the root cause is available in the Apache Tomcat/7.0.16 logs.Apache Tomcat/7.0.16

答案

服务器端应用程序出错,具体出错位置是LoginDao第27行代码附近,错误原因是空指针异常,原因是27行某一个对象未进行初始化