Serlvet学习笔记之三—数据库的操作

import java.sql.*;
import java.io.*;
import javax.servlet.http.*;
public class Logincl extends HttpServlet{
    public void doGet(HttpServletRequest req,HttpServletResponse res){
        Connection ct=null;
        Statement sm=null;
        ResultSet rs=null;
        try {
            String u=req.getParameter("username");
            String p=req.getParameter("passwd");
//连接Oracle数据库
            Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
             ct=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:mydev","dev1","dev1");
             sm=ct.createStatement();
             rs=sm.executeQuery("select passwd from users where username=‘"+u+"‘");
            //注入漏洞("select * from users where username=‘"+u+"‘ and passwd=‘"+p+"‘ or 1=‘"+1+"‘");
            if(rs.next()){
                String dbPasswd=rs.getString(1);
                if(dbPasswd.equals(p)){
                    res.sendRedirect("welcome");
                }
            }else {
                res.sendRedirect("login");  //跳转的URL
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally{　　　　　　　　　　　　　　　　　//关闭数据库资源
            try {
                if(rs!=null){
                    rs.close();
                }
                if(sm!=null){
                    sm.close();
                }
                if(ct!=null){
                   ct.close();
                }
            } catch (Exception ce) {
                ce.printStackTrace();
            }
        }
    }
    public void doPost(HttpServletRequest req,HttpServletResponse res){
        this.doGet(req, res);
        }
}