实现数据暴露

三层，层层调用，不可越级调用

数据链路层（dao)---服务层---控制层（servlet)

1.配置Tomcat

2.UserinfosDAO+

public Userinfos login(String username, String pwd){
        String sql="select * from userinfos where username=? and pwd=?";
        List<Userinfos> uss=change(sql,new Object[]{username,pwd});
        return uss.isEmpty()?null:uss.get(0);
  }

3.接口UserinfosService

4.接口实现类

package com.zbitedu.abc.services.impl;

import com.alibaba.fastjson.JSONObject;
import com.zbitedu.abc.dao.UserinfosDAO;
import com.zbitedu.abc.entity.Userinfos;
import com.zbitedu.abc.services.UserinfosService;

import java.util.List;

public class UserinfosServiceImpl implements UserinfosService {
    private UserinfosDAO userinfosDAO;

    public UserinfosServiceImpl() {
        userinfosDAO=new UserinfosDAO();
    }

    @Override
    public Userinfos userLogin(String username, String pwd) {
        return userinfosDAO.login(username, pwd);
    }

5.new Servlet:LoginServlet

6.web.xml添加

<servlet-mapping>
        <servlet-name>/*和上面已有的一样*/</servlet-name>
        <url-pattern>/login</url-pattern>  //自定义
</servlet-mapping>
 

7.LoginServlet

public class LoginServlet extends HttpServlet {
    private UserinfosService userinfosService;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //接受
        String name = request.getParameter("name");
        String pwd = request.getParameter("pwd");
        //调
        userinfosService=new UserinfosServiceImpl();
        Userinfos us = userinfosService.userLogin(name, pwd);
        //回
        PrintWriter out = response.getWriter();
        out.println(us!=null?"success":"fail");
        out.close();
    }

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