跳转：
<form action="UserHandleServlet?flag=xiugai" >
<input type="submit" name="submit "value="提交" onclick="return window.confirm('确认提交吗?')">
</form>
接收:
String flag=request.getParameter("flag");
结果说flag是空指针异常：
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NullPointerException
com.zkf.controller.UserHandleServlet.doGet(UserHandleServlet.java:19)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.14 logs.
处理提问