server-jsp報錯-loginProcess.jsp at line 29

jsp報錯-loginProcess.jsp at line 29

type Exception report

message An exception occurred processing JSP page /loginProcess.jsp at line 29

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /loginProcess.jsp at line 29

26:

27: List> alist=db.list(sql);
28: int temp=0;
29: for(int i=0;i<alist.size();i++){
30: String str=alist.get(i).get("num").toString();
31: temp=Integer.parseInt(str);
32: }

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
root cause

java.lang.NullPointerException
org.apache.jsp.loginProcess_jsp._jspService(loginProcess_jsp.java:90)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:728)

最佳回答：

這個我也指點不了啊，你debug下程序，單步執行看看變量的值