javaweb网上书店开发之异常处理----org.apache.catalina.core.StandardWrapperValve invoke

  在服务器端Servlet处获取验证码时，抛出如下异常：

2011-11-30 21:23:24 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet adminLoginServlet threw exception
java.lang.NullPointerException
 at com.weiyi.book.servlet.admin.adminLoginServlet.doPost(adminLoginServlet.java:87)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
 at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
 at java.lang.Thread.run(Thread.java:619)
以及：

 

查了百度，有说事数据库版本、apache版本过低的什么（本人觉得不可能），最后听了一位学长的话去按着流程走了遍才发现原来在Servlet端获取表单验证码时，方法用错了，如下所示：

 /*获取管理员表单输入的账号和密码*/
  String adminName = (String)request.getParameter("username");
  String adminPwd = (String)request.getParameter("passwd");
  String valid = (String)request.getAttribute("authcode");//getAttribute应该为getParameter();

 

我只能说表示很尴尬。。。。。