public class UserInfo {
     private Integer userCode;
     private String userName;
     private String userPwd;
     private Date lastLoginTime;
     private boolean isUse;
     //alt+insert

    public Integer getUserCode() {
        return userCode;
    }

    public void setUserCode(Integer userCode) {
        this.userCode = userCode;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserPwd() {
        return userPwd;
    }

    public void setUserPwd(String userPwd) {
        this.userPwd = userPwd;
    }

    public Date getLastLoginTime() {
        return lastLoginTime;
    }

    public void setLastLoginTime(Date lastLoginTime) {
        this.lastLoginTime = lastLoginTime;
    }

    public boolean isUse() {
        return isUse;
    }

    public void setUse(boolean use) {
        isUse = use;
    }
}

package cn.blog.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;


/**
 * 数据访问工具类
 * @version 1.1
 * @author happy
 *
 */
public class BaseDao {
	// 01. 基础内容的准备
	private static final String driver="com.mysql.jdbc.Driver";
	private static final String url="jdbc:mysql:///wk";
	private static final String username="root";
	private static final String pwd="";

	//02, 接口对象的准备
	Connection con=null;
	PreparedStatement ps=null;
	public ResultSet rs=null;

	/**
	 * 01.写一个用户获取到一个连接对象的方法，方法的返回值是Connection类型
	 * @return   连接对象
	 * @throws Exception
	 */
	public Connection getConnection() throws Exception{
		Class.forName(driver);
		//什么条件下，构建connection对象
		if (con==null||con.isClosed()) {
			con=DriverManager.getConnection(url, username, pwd);
		}
		//同志们碰到一个
		return con;
	}




	/**
	 * 执行查询操作  目的：返回一个读取器
	 * @param sql  sql语句
	 * @param objs  参数列表
	 * @return     读取器对象
	 * @throws Exception
	 */
	public ResultSet  executeQuery(String sql,Object... objs) throws Exception{
		con=getConnection();
		ps = con.prepareStatement(sql);
		for (int i = 0; i < objs.length; i++) {
			ps.setObject(i+1, objs[i]);
		}
		rs= ps.executeQuery();
		return rs;
	}

	/**
	 * 执行增删该操作
	 * @param sql  sql语句
	 * @param objs  参数列表
	 * @return     受影响行数
	 * @throws Exception
	 */
	public int executeUpdate(String sql,Object... objs) throws Exception{
		con=getConnection();
		ps = con.prepareStatement(sql);
		for (int i = 0; i < objs.length; i++) {
			ps.setObject(i+1, objs[i]);
		}
		int count = ps.executeUpdate();
		return count;
	}




	/**
	 * 回收连接资源
	 * @throws Exception
	 */
	public void closeAll() throws Exception{
		//倒着回收
		if(rs!=null){
			rs.close();
		}
		if (ps!=null) {
			ps.close();
		}
		if(con!=null){
			con.close();
		}
	}

}

package cn.blog.dao.iimpl;

import cn.blog.dao.BaseDao;
import cn.blog.dao.IUserInfoDAO;
import cn.blog.entity.UserInfo;
import org.junit.Test;


import java.sql.ResultSet;

/**
 * Created by Happy on 2017-06-30.
 */
public class UserInfoDAOImpl extends BaseDao implements IUserInfoDAO {


    @Test
   public void testIsLogin(){
       UserInfo info=new UserInfo();
       info.setUserCode(11);
       info.setUserPwd("123");
       try {
           boolean flag = isLogin(info);
           System.out.println(flag);
       } catch (Exception e) {
           e.printStackTrace();
       }
   }


    public boolean isLogin(UserInfo info) throws Exception {
        boolean flag=false;
        //根据用户名和密码查看复合条件的记录有几条》》》》》》》》》》》》》》
        String  sql="select count(1) as UserCode from userInfo where UserCode=? and UserPwd=?";
        Object[] paras={info.getUserCode(),info.getUserPwd()};
        ResultSet rs = executeQuery(sql, paras);
        if (rs.next()){
            if (rs.getInt("UserCode")>0){
                flag=true;
            }
        }
        return flag;
    }



}

package cn.blog.servlet;

import cn.blog.dao.IUserInfoDAO;
import cn.blog.dao.iimpl.UserInfoDAOImpl;
import cn.blog.entity.UserInfo;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * Created by Happy on 2017-06-30.
 */
public class UserInfoServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //write code here please ,oK?
        //使用dao实现类
        IUserInfoDAO dao=new UserInfoDAOImpl();
        String userCode=request.getParameter("userCode");
        String userPwd=request.getParameter("userPwd");
        UserInfo info=new UserInfo();
        System.out.println(userCode+"===================");
        info.setUserCode(Integer.parseInt(userCode));
        info.setUserPwd(userPwd);
        try {
            boolean flag = dao.isLogin(info);
            if (flag){
                request.getRequestDispatcher("/BlogHtTemplate-master/html/main.html").forward(request,response);
            }else{
                response.sendRedirect("/BlogHtTemplate-master/html/index.html");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        //  dao.isLogin();
        //跳转

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}