请问一下各位高手，这个是什么错误？？？

Question

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
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:512)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:395)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause java.lang.NullPointerException
smis.tool.showByPage.set(showByPage.java:16)
org.apache.jsp.pages.list_jsp._jspService(list_jsp.java:89)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:334)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.20 logs.

Answer 1

java.lang.NullPointerException空指针异常啊 

Answer 2

showByPage这个类你们自己写的吧，第16行报错，进去看看。

Answer 3

list_jsp.java:89(Tomcat5.0\work\Catalina\localhost\项目名称\org\apache\jsp)找到这个文件，看看这行代码，报的是空指针异常

Answer 4

java.lang.NullPointerException空指针异常smis.tool.showByPage.set(showByPage.java:16)
看看这行
应该是没有值或是找不到

Answer 5

lz贴些代码上来嘛
NullPointerException