不知道怎么调试
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><jsp:useBean id="sqlbean" scope="page" class="com.chrkey.bean.SqlConn" /><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>My JSP 'modifyto.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <% String admin_id =((String)session.getAttribute("admin_id")).trim(); String passwd_old = new String(request.getParameter("passwd_old").trim().getBytes(), "UTF-8"); String passwd_new = new String(request.getParameter("passwd_new").trim().getBytes(), "UTF-8"); String passwd_confirm = new String(request.getParameter("passwd_confirm").trim().getBytes(), "UTF-8"); if (!passwd_confirm.equals(passwd_new)) out.println("确认新密码错误"); else{ String sql="update admin set passwd='"+passwd_new+"' where id='"+admin_id+"' and passwd='"+passwd_old+"' "; sqlbean.executeUpdate(sql); response.sendRedirect("adms.jsp"); } %> </body></html> String admin_id =((String)session.getAttribute("admin_id")).trim(); String passwd_old = new String(request.getParameter("passwd_old").trim().getBytes(), "UTF-8"); String passwd_new = new String(request.getParameter("passwd_new").trim().getBytes(), "UTF-8"); String passwd_confirm = new String(request.getParameter("passwd_confirm").trim().getBytes(), "UTF-8");其中一行空指针了。。。如何debug？首先debug方式启动，然后只要在java代码行最前面，双击设置一个断点。。。就可以调试了。。。