空指针？

Question

程序在本地上运行没有错误，可到了服务器后程序有时出现空指针有时正常，那位大哥告诉小弟一下是什么原因？？？？？

Answer 1

HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:541)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:435)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.shimin.util.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:46)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1063)
org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:386)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:229)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:414)
org.shimin.lawon.common.filter.ResponseTo80.doFilter(ResponseTo80.java:40)
org.shimin.util.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:46)
root cause java.lang.NullPointerException
web.dao.DBConnection.executeQuery(DBConnection.java:28)
web.dao.user.UserSort.query(UserSort.java:256)
org.apache.jsp.web.usermanager.index_jsp._jspService(index_jsp.java:87)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.shimin.util.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:46)
org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1063)
org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:386)
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:229)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:414)
org.shimin.lawon.common.filter.ResponseTo80.doFilter(ResponseTo80.java:40)
org.shimin.util.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:46)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.
--------------------------------------------------------------------------------Apache Tomcat/6.0.13

Answer 2

web.dao.DBConnection.executeQuery(DBConnection.java:28)
这里出现问题了 查询数据库出现

Answer 3

是连接为null？但有一般时候还是好用的

Answer 4

不是你sql语句有问题就是你服务器的表里面有问题了,查查吧

Answer 5

获取连接失败，不过奇怪的是没有SQL异常，
建议你使用远程调试跟踪一下，这类问题不难解决。