我在这个阶段将后台的代码进行了一下晚上因为需要一个模糊搜索，所以需要连接数据库进行前后端的交互

Servlet.java

package servlet;

import java.io.IOException;

import java.util.List;

import java.io.PrintWriter;

import javax.security.auth.message.callback.PrivateKeyCallback.Request;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import dao.*;

import bean.*;

@WebServlet("/r2")

public class Servlet extends HttpServlet{

public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, java.io.IOException {

        return;

    }

    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");// 设置字符集，避免乱码

        // 获取jsp界面需要进行的操作，

        String method = req.getParameter("method");

        //System.out.println("============");

        if (method.equals("zhuce"))

        {

         adduser(req,resp);

        }

        if (method.equals("denglu"))

        {

         denglu(req,resp);

        }

        if (method.equals("sousuo"))

        {

         sousuo(req,resp);

        }

        if (method.equals("dianzan"))

        {

         dianzan(req,resp);

        }

    }

    private void adduser(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");

           resp.setContentType("text/html;charset=utf-8");

           String username=req.getParameter("username");

           String password = req.getParameter("password");

           String number=req.getParameter("number");

           String email=req.getParameter("email");

           String sex=req.getParameter("sex");

           String age=req.getParameter("age");

           String weight=req.getParameter("weight");

           System.out.println(username);

           dao  userdao = new dao();

           System.out.println("============");

           userdao.adduser(number,password,number,email,sex,age,weight);

           System.out.println("============");

           req.getRequestDispatcher("/login.jsp").forward(req,resp);

      }

    private void denglu(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

       req.setCharacterEncoding("utf-8");

          resp.setContentType("text/html;charset=utf-8");

          String username=req.getParameter("username");

          String password = req.getParameter("password");

          System.out.println(username);

          dao userdao = new dao();

          String w= userdao.login(username,password);

          if(w.equals("正确"))

          {

           req.getRequestDispatcher("daohang.jsp").forward(req,resp);

          }

          else {

           req.setAttribute("message", "账号或密码错误，请重新输入。");

           req.getRequestDispatcher("login.jsp").forward(req,resp);

          }

     }

    private void sousuo(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");

        String name=req.getParameter("name");

//        System.out.println(req.getParameter("luxian")+"=========");

        List<Food2> kc=dao.sousuo(name);

        req.setAttribute("kc", kc);

        //req.setAttribute("inf1", inf1);

        req.getRequestDispatcher("sousuo.jsp").forward(req, resp);

    }

    private void dianzan(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");

           resp.setContentType("text/html;charset=utf-8");

           String name=req.getParameter("name");

           dao  userdao = new dao();

          // System.out.println("============");

           userdao.dianzan(name);

          // System.out.println("============");

           req.setAttribute("message", "点赞成功");

           req.getRequestDispatcher("/daohang.jsp").forward(req,resp);

      }

 }

Dao.java

package dao;

import java.sql.Connection;

import java.util.ArrayList;

import java.util.List;

import java.sql.ResultSet;

import java.sql.Statement;

import dbutil.DBUtil;

import bean.*;

import java.util.Collections;

public class dao {

public int adduser(String username,String password,String number,String email,String sex,String age,String weight)

    {

        Connection conn = DBUtil.getConn();//这里就是从DBUtil类里面得到连接

        Statement state =null;

        ResultSet rs = null;

        int flag=0;

        try

        {

            String sql = "insert into user(username,password,number,email,sex,age,weight)values('"+username+"','"+password+"','"+number+"','"+email+"','"+sex+"','"+age+"','"+weight+"')";

            state = conn.createStatement();

            int count = state.executeUpdate(sql);

            if(count>0) {

                System.out.println("数据插入成功");

            }else {

                System.out.println("数据插入失败了QAQ");

            }

        }

        catch(Exception e)

        {

            e.printStackTrace();

        }

        finally

        {

            DBUtil.close(rs, state, conn);

        }

        return flag;

    }

public String login(String name,String paw)

    {

        Connection conn = DBUtil.getConn();//这里就是从DBUtil类里面得到连接

        Statement state =null;

        ResultSet rs = null;

        try

        {

            String sql = "select * from user";

            state = conn.createStatement();

            rs=state.executeQuery(sql);

            while(rs.next())

            {

             String number=rs.getString("username");

             String password=rs.getString("password");

             if(number.equals(name)&&password.equals(paw))

             {

             return "正确";

             }

            }

        }

        catch(Exception e)

        {

            e.printStackTrace();

        }

        finally

        {

            DBUtil.close(rs, state, conn);

        }

        return "错误";

    }

public static List<Food2> sousuo(String name)

    {

String sql = "select * from food join windows on food.position=windows.WPosition where foodname like '%"+name+"%' or WName like '%"+name+"%'";

        Connection conn = DBUtil.getConn();//这里就是从DBUtil类里面得到连接

        Statement state =null;

        List<Food2> list = new ArrayList<>();

        ResultSet rs = null;

        int flag=0;

        try

        {

            state = conn.createStatement();

            rs=state.executeQuery(sql);

            Food2 kc=null;

            while(rs.next())

            {

             int WId=rs.getInt("WId");

             String WPosition=rs.getString("WPosition");

             String WName=rs.getString("WName");

             int id=rs.getInt("id");

             String foodname=rs.getString("foodname");

             double price=rs.getDouble("price");  

             String kind=rs.getString("kind");

             //String img=rs.getString("img");

             int score=rs.getInt("score");

             kc =new Food2(WId,WPosition,price,WName,id,kind,foodname,/*img,*/score);

             System.out.println(kc);

             list.add(kc);

            }

        }

        catch(Exception e)

        {

            e.printStackTrace();

        }

        finally

        {

            DBUtil.close(rs, state, conn);

        }

        return list;

    }

public int dianzan(String name)

    {

        Connection conn = DBUtil.getConn();//这里就是从DBUtil类里面得到连接

        Statement state =null;

        ResultSet rs = null;

        int flag=0;

        //System.out.println(name);

        try

        {

            String sql = "update windows set score=score+1 where WName='"+name+"'";

            state = conn.createStatement();

            int count = state.executeUpdate(sql);

            if(count>0) {

                System.out.println("数据插入成功");

            }else {

                System.out.println("数据插入失败了QAQ");

            }

        }

        catch(Exception e)

        {

            e.printStackTrace();

        }

        finally

        {

            DBUtil.close(rs, state, conn);

        }

        return flag;

    }

}