学了几个月java ,头一次被整的要疯掉了。
有时候有数据，有时候又没有，现在连登录都不可以了。ConDB没有改动。数据库可以连上，
package com.nong;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.util.*;import java.sql.*;public class LoginCL extends HttpServlet{public void doGet(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException{ String u=req.getParameter("username"); String p=req.getParameter("passwd"); //UserBeanCL ubc=new UserBeanCL(); ConDB db=new ConDB(); db.closeall();//为了确保上一次没有断开的连接断开 if(db.isExist("select * from users")) { res.setContentType("text/html;charset=gbk"); PrintWriter pw=res.getWriter(); ConDB db1=new ConDB(); try{ ResultSet rs1=db1.getRset("select * from student"); while(rs1.next()) { pw.println("aa"); } try{ rs1.close(); } catch(Exception e) {e.printStackTrace();} } catch(Exception e) { e.printStackTrace(); } db1.closeall(); db.closeall(); /* Cookie name=new Cookie("myname",u); Cookie pass=new Cookie("mypasswd",p); name.setMaxAge(14*24*3600); pass.setMaxAge(14*24*3600); res.addCookie(name); res.addCookie(pass); HttpSession hs=req.getSession(true); hs.setMaxInactiveInterval(14*24*3600); hs.setAttribute("myname",u); hs.setAttribute("mypasswd",p); HttpSession hh=req.getSession(false); pw.println("你好"+(String)hh.getAttribute("myname")); int pageSize=2; int pageNow=1; UserBeanCL ubb=new UserBeanCL(); ArrayList al=ubb.getResultBypage(pageNow,pageSize); pw.println(al.size()); pw.println("<table border=1>"); pw.println("<tr><th>id</th><th>name</th><th>age</th><th>score</th></tr>"); for(int i=0;i<al.size();i++) { UserBean ub=(UserBean)al.get(i); pw.println("<tr>"); pw.println("<td>"+ub.getID()+"</td>"); pw.println("<td>"+ub.getName()+"</td>"); pw.println("<td>"+ub.getAge()+"</td>"); pw.println("<td>"+ub.getScore()+"</td>"); pw.println("</tr>"); } pw.println("</table>"); */ } else { res.sendRedirect("http://www.baidu.com"); }}public void doPost(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException{ this.doGet(req,res);} }package com.nong;import java.sql.*;public class ConDB {private Connection ct=null;private PreparedStatement pm=null;private ResultSet rs=null;public Connection getConn(){ try { Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver"); ct=DriverManager.getConnection("jdbc:microsoft:sqlserver://127.0.0.1:1434;DatabaseName=Mybase","sa","long"); } catch(Exception e) {e.printStackTrace();} return ct;}public ResultSet getRset(String sqlstr){ try { ct=getConn(); pm=ct.prepareStatement(sqlstr); rs=pm.executeQuery(); } catch(Exception e) {e.printStackTrace();} finally { return rs; }}public boolean isExist(String strsql){ boolean b=false; try { ct=this.getConn(); pm=ct.prepareStatement(strsql); rs=pm.executeQuery(); if(rs.next()) { b=true; } } catch(Exception ex) { ex.printStackTrace(); } finally { return b; } }public void closeall(){ try{ if(this.rs!=null){rs.close();this.rs=null;} if(this.pm!=null){pm.close();this.pm=null;} if(this.ct!=null){ct.close();this.ct=null;}}catch(Exception e){e.printStackTrace();}} }