JavaWeb项目一：小型论坛

这篇文章本来是写给zyan看的，粉丝可见，后来发现CSDN需要一千字才可粉丝可实现见这个功能，所以；
shuishuiwenwenshuishuiwenwen
shuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenweshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwenshuishuiwenwen

这里的关注功能没写，需求不太好，想写的更好又懒，由于数据库的设计，只有三个表，因此如果想实现点赞不累加，需要另外的表进行检索判断
数据库的设计非常的重要

留言.Dao

package com.edu.zut.dao;

import com.edu.zut.entity.Liuyan;
import com.edu.zut.utils.DateUtil;
import com.edu.zut.utils.JDBUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class LiuyanDao {
    public static List getLiuyans(Integer tid){
        List list = new ArrayList();
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        ResultSet rs=null;
        Liuyan liuyan=null;
        try {
            ps=connection.prepareStatement("select * from liuyan where tid=?");
            ps.setInt(1,tid);
            rs=ps.executeQuery();
            while (rs.next()){
                liuyan= new Liuyan(rs.getInt(1), DateUtil.getForDate(rs.getTimestamp(2)), rs.getInt(3),rs.getInt(4) ,rs.getString(5),rs.getInt(6),rs.getString(7));
                list.add(liuyan);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,rs,ps);
        return list;
    }
    public static int insertLiuYan(Integer tid, String uname, String lneirong){
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        int result=0;
        try {
            ps=connection.prepareStatement("insert into liuyan(lneirong,tid,uname) value(?,?,?)");
            ps.setString(1,lneirong);
            ps.setInt(2,tid);
            ps.setString(3,uname);
            result = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,null,ps);
        return result;
    }
    //修改赞/踩
    public static int updateSupport(Integer tid,Integer lid){
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        int result=0;
        try {
            ps=connection.prepareStatement("update liuyan set support=support+1 where tid=? and lid=?");
            ps.setInt(1,tid);
            ps.setInt(2,lid);
            result = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,null,ps);
        return result;
    }
    //修改赞/踩
    public static int updateOppose(Integer tid,Integer lid){
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        int result=0;
        try {
            ps=connection.prepareStatement("update liuyan set oppose=oppose+1 where  tid=? and lid=?");
            ps.setInt(1,tid);
            ps.setInt(2,lid);
            result = ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,null,ps);
        return result;
    }
}

话题.dao

package com.edu.zut.dao;

import com.edu.zut.entity.Topic;
import com.edu.zut.utils.DateUtil;
import com.edu.zut.utils.JDBUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

public class TopicDao {

    public static List getTopics(){
        List list = new ArrayList();
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        ResultSet rs=null;
        Topic topic=null;
        try {
            ps=connection.prepareStatement("select * from topic");
            rs=ps.executeQuery();
            while (rs.next()){
                topic= new Topic(rs.getInt(1), rs.getString(2), rs.getString(3), DateUtil.getForDate(rs.getTimestamp(4)), rs.getInt(5), rs.getString(6));
                list.add(topic);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,rs,ps);
        return list;
    }
    //根据tid查询话题详情
    public static Topic getTopic(Integer tid){
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        ResultSet rs=null;
        Topic topic=null;
        try {
            ps=connection.prepareStatement("select * from topic where tid=?");
            ps.setInt(1,tid);
            rs=ps.executeQuery();
            if (rs.next()){
                topic= new Topic(rs.getInt(1), rs.getString(2), rs.getString(3), DateUtil.getForDate(rs.getTimestamp(4)), rs.getInt(5), rs.getString(6));
                return topic;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,rs,ps);
        return null;
    }
    //获取最新创建的话题的id，原理：登录者创建的话题的id倒序，获取第一个，即是最新创建的话题
    public static Integer getTid(String uname){
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        ResultSet rs=null;
        try {
            ps=connection.prepareStatement("select tid from topic where uname=? order by tid desc limit 1");
            ps.setString(1,uname);
            rs=ps.executeQuery();
           if(rs.next()){
               //直接返回id
                return rs.getInt("tid");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,rs,ps);
        //没有创建成功返回-1
        return -1;
    }
    public static int deleteTopic(Integer tid,String uname){
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        int result=0;
        try {
            ps=connection.prepareStatement("delete from topic where tid=? and uname=?");
            ps.setInt(1,tid);
            ps.setString(2,uname);
            result=ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,null,ps);
        return result;
    }
    public static int insertTopic(String title,String tneirong,String uname){
        Connection connection = JDBUtil.getCon();
        PreparedStatement ps= null;
        int result=0;
        try {
            ps=connection.prepareStatement("insert into topic(title,tneirong,uname) value(?,?,?)");
            ps.setString(1,title);
            ps.setString(2,tneirong);
            ps.setString(3,uname);
            result=ps.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(connection,null,ps);
        return result;
    }
}

用户.dao

package com.edu.zut.dao;

import com.edu.zut.entity.User;
import com.edu.zut.utils.JDBUtil;

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

public class UserDao {

    public static int selectUser(String uname,String upwd){
        Connection con= JDBUtil.getCon();
        String sql="select * from user where uname=? and upwd =?";
        PreparedStatement ps=null;
        ResultSet rs=null;
        try {
            ps=con.prepareStatement(sql);
            ps.setString(1,uname);
            ps.setString(2,upwd);
            rs=ps.executeQuery();
            if(rs.next()){
                return 1;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBUtil.close(con,rs,ps);
        return 0;
    }
}

Entity User.java

package com.edu.zut.entity;
import java.io.Serializable;

public class User implements Serializable {
    private String uname;
    private String upwd;

    public User(String uname, String upwd) {
        this.uname = uname;
        this.upwd = upwd;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    public String getUpwd() {
        return upwd;
    }

    public void setUpwd(String upwd) {
        this.upwd = upwd;
    }

    @Override
    public String toString() {
        return "User{" +
                "uname='" + uname + ''' +
                ", upwd='" + upwd + ''' +
                '}';
    }
}

Topic.java

package com.edu.zut.entity;
import com.edu.zut.utils.DateUtil;

import java.io.Serializable;
import java.util.Date;

public class Topic implements Serializable {
    private Integer tid;
    private String title;
    private String tneirong;
    private Date tdate;
    private Integer renshu;
    private String uname;

    public Topic(Integer tid, String title, String tneirong, Date tdate, Integer renshu, String uname) {
        this.tid = tid;
        this.title = title;
        this.tneirong = tneirong;
        this.tdate = tdate;
        this.renshu = renshu;
        this.uname = uname;
    }

    public Integer getTid() {
        return tid;
    }

    public void setTid(Integer tid) {
        this.tid = tid;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getTneirong() {
        return tneirong;
    }

    public void setTneirong(String tneirong) {
        this.tneirong = tneirong;
    }

    public Date getTdate() {
        return tdate;
    }

    public void setTdate(Date tdate) {
        this.tdate = tdate;
    }

    public Integer getRenshu() {
        return renshu;
    }

    public void setRenshu(Integer renshu) {
        this.renshu = renshu;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    @Override
    public String toString() {
        return "Topic{" +
                "tid=" + tid +
                ", title='" + title + ''' +
                ", tneirong='" + tneirong + ''' +
                ", tdate=" + tdate +
                ", renshu=" + renshu +
                ", uname='" + uname + ''' +
                '}';
    }

}

Liuyan.java

package com.edu.zut.entity;
import java.io.Serializable;
import java.util.Date;

public class Liuyan implements Serializable {
    private Integer lid;
    private Date ldate; //留言日期
    private Integer support; //支持人数
    private Integer oppose; //反对人数
    private String lneirong; //留言内容
    private Integer tid; //话题
    private String uname; //用户名

    public Liuyan(Integer lid, Date ldate, Integer support, Integer oppose, String lneirong, Integer tid, String uname) {
        this.lid = lid;
        this.ldate = ldate;
        this.support = support;
        this.oppose = oppose;
        this.lneirong = lneirong;
        this.tid = tid;
        this.uname = uname;
    }

    public Integer getLid() {
        return lid;
    }

    public void setLid(Integer lid) {
        this.lid = lid;
    }

    public Date getLdate() {
        return ldate;
    }

    public void setLdate(Date ldate) {
        this.ldate = ldate;
    }

    public Integer getSupport() {
        return support;
    }

    public void setSupport(Integer support) {
        this.support = support;
    }

    public Integer getOppose() {
        return oppose;
    }

    public void setOppose(Integer oppose) {
        this.oppose = oppose;
    }

    public String getLneirong() {
        return lneirong;
    }

    public void setLneirong(String lneirong) {
        this.lneirong = lneirong;
    }

    public Integer getTid() {
        return tid;
    }

    public void setTid(Integer tid) {
        this.tid = tid;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    @Override
    public String toString() {
        return "Liuyan{" +
                "lid=" + lid +
                ", ldate=" + ldate +
                ", support=" + support +
                ", oppose=" + oppose +
                ", lneirong='" + lneirong + ''' +
                ", tid=" + tid +
                ", uname='" + uname + ''' +
                '}';
    }
}

Service层删除话题

package com.edu.zut.service;

import com.edu.zut.dao.TopicDao;
import com.edu.zut.dao.UserDao;
import com.edu.zut.entity.Topic;

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

public class DeleteTopic extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置编码，必须放在头部
        resp.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=utf-8");
        Integer tid=Integer.parseInt(req.getParameter("tid"));
        HttpSession session = req.getSession();
        String uname= (String) session.getAttribute("uname");
        int result= TopicDao.deleteTopic(tid,uname);
        if(result==1){
            resp.getWriter().print("");
            resp.setHeader("refresh","2;/page2");
        }else{
            resp.getWriter().print("");
            resp.setHeader("refresh","2;/page2");
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
}

话题详情

package com.edu.zut.service;
import com.edu.zut.dao.LiuyanDao;
import com.edu.zut.dao.TopicDao;
import com.edu.zut.entity.Liuyan;
import com.edu.zut.entity.Topic;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;


public class DetailTopic extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //添加之后跳转到详情页面，设置方式是setAttrbute()
        Integer tid=(Integer)(req.getAttribute("detailid"));
        //点击超链接里的查看，跳转后，获取方式是getParam
        if(req.getParameter("option")!=null){
            if(req.getParameter("option").equals("detail")){
                tid=Integer.parseInt(req.getParameter("detailid"));
            }
        }
        System.out.println("detail"+tid);
        Topic topic=TopicDao.getTopic(tid);
        List liuyanlist = LiuyanDao.getLiuyans(tid);
        req.setAttribute("topic",topic);
        req.setAttribute("liuyanlist",liuyanlist);
        req.getRequestDispatcher("/jsp/detail.jsp").forward(req,resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}

留言

package com.edu.zut.service;

import com.edu.zut.dao.LiuyanDao;
import com.edu.zut.utils.DateUtil;

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


public class InsertLiuyan extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        HttpSession httpSession= req.getSession();
        //获取uname,lneirong,ldate
        Date ldate= new Date();
        String uname= (String) httpSession.getAttribute("uname");
        Integer tid =Integer.parseInt(req.getParameter("tid"));
        String lneirong=req.getParameter("lneirong");
        System.out.println("liuyan:"+uname+tid+lneirong+DateUtil.getString(new Date()));
        //添加
        LiuyanDao.insertLiuYan(tid,uname,lneirong);
        req.setAttribute("detailid",tid);
        //转到详情页，重新检索数据库的留言信息
        req.getRequestDispatcher("/detail").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
}

添加话题

package com.edu.zut.service;

import com.edu.zut.dao.TopicDao;

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

//@RequestMapping("/insert")
public class InsertTopic extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置编码，必须放在头部
        resp.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=utf-8");
        String title=req.getParameter("title");
        String tneirong=req.getParameter("tneirong");
        String uname= String.valueOf(req.getSession().getAttribute("uname"));
        int result=TopicDao.insertTopic(title,tneirong,uname);
        if(result==1){
            resp.getWriter().print("");
            //查询话题的id号
            int tid=TopicDao.getTid(uname);
            if(tid!=-1){
                req.setAttribute("detailid",tid);
                req.getRequestDispatcher("/detail").forward(req,resp);
            }
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}

package com.edu.zut.service;
import com.edu.zut.dao.UserDao;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

public class login extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //设置编码，必须放在头部
        resp.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=utf-8");
        String uname=req.getParameter("uname");
        String upwd=req.getParameter("upwd");
        if(UserDao.selectUser(uname,upwd)==1){
            HttpSession session= req.getSession();
            session.setAttribute("uname",uname);
            session.setAttribute("upwd",upwd);
            resp.sendRedirect("/page2");
        }else {
            resp.getWriter().print("");
            resp.setHeader("refresh","2;/login.html");
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req,resp);
    }
}

展示所有话题

package com.edu.zut.service;

import com.edu.zut.dao.TopicDao;
import com.edu.zut.entity.Topic;

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


public class PageTwo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List list = TopicDao.getTopics();
        req.setAttribute("list",list);
        req.getRequestDispatcher("/jsp/topics.jsp").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }
}

点赞或踩的修改

package com.edu.zut.service;

import com.edu.zut.dao.LiuyanDao;

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

public class Support extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        if(req.getParameter("option")!=null){
            Integer tid =Integer.parseInt(req.getParameter("tid"));
            Integer lid =Integer.parseInt(req.getParameter("lid"));
            if(req.getParameter("option").equals("1")){
                LiuyanDao.updateSupport(tid,lid);
            }else{
                LiuyanDao.updateOppose(tid,lid);
            }
            req.setAttribute("detailid",tid);
            //转到详情页，重新检索数据库的留言信息
            req.getRequestDispatcher("/detail").forward(req,resp);
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       doPost(req, resp);
    }
}

Util层日期处理

package com.edu.zut.utils;

import java.sql.Timestamp;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DateUtil {
   public static SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

   public static String getString(Date date){
       String string= sdf.format(date);
       return string;
   }
   public static Date getDate(String string) {
       Date date = null;
       try {
           date = sdf.parse(string);
       } catch (ParseException e) {
           e.printStackTrace();
       }
       return date;
   }
   
   public static Date getForDate(java.sql.Timestamp date){
       //保存的是的是对应时分秒格式的date
       Date date1=  DateUtil.getDate(DateUtil.getString(new Date(date.getTime())));
       return date1;
   }
   
   public static java.sql.Timestamp getForDate2(Date date1){
       java.sql.Timestamp date =new java.sql.Timestamp(date1.getTime());
        return date;
   }
}

JDBC

package com.edu.zut.utils;

import java.sql.*;

public class JDBUtil {
    private static String className,url,name,pwd;
    static {
        className="com.mysql.jdbc.Driver";
        url="jdbc:mysql://localhost:3306/luntan?useUnicode=true&characterEncoding=utf-8&userSSL=false";
        name="root";
        pwd="123456";
    }
    static {
        try {
            Class.forName(className);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

    }
    public static Connection getCon(){
        Connection connection=null;
        try {
            connection = DriverManager.getConnection(url,name,pwd);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return connection;
    }

    public static void close(Connection connection,ResultSet resultSet ,PreparedStatement preparedStatement){
        try {
            if(resultSet!=null){resultSet.close();}
            if(preparedStatement!=null){  preparedStatement.close();}
            if(connection!=null){connection.close();}
        } catch (SQLException e) {
            throw new RuntimeException();
        }
    }
}

Web页面 /jsp

<%@ page import="com.edu.zut.entity.Topic" %><%--
  Created by IntelliJ IDEA.
  User: hi
  Date: 2022/4/20
  Time: 10:17
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>



    
    话题详情页


<%@page import="com.edu.zut.utils.DateUtil" %>

    话题${requestScope.topic.title}的详情页面



    
        ${requestScope.topic.title}
    
    
        作者:${requestScope.topic.uname} |
        时间：${DateUtil.getString(requestScope.topic.tdate)} |
        关注：${requestScope.topic.renshu}
    
    


    
        ${requestScope.topic.tneirong}
    


    
    
        
            ${liuyan.uname}
            ${DateUtil.getString(liuyan.ldate)}
            赞:${liuyan.support}
            踩:${liuyan.oppose} 
        
        
            
                ${liuyan.lneirong}

topics.jsp展示所有

<%--
  Created by IntelliJ IDEA.
  User: hi
  Date: 2022/4/19
  Time: 23:21
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="ftm" uri="http://java.sun.com/jsp/jstl/fmt" %>


    所有话题的展示！
    


    <%@page import="com.edu.zut.entity.Topic"%>
    <%@ page import="java.util.*" %>
    <%@page import="com.edu.zut.utils.DateUtil" %>
    <%
        List list = (List) request.getAttribute("list");
    %>
    
            
        
            
                添加话题
            
        
        
            顺序
            编号
            标题
            关注
            时间
            作者
            操作
            查看详情
        
        
                ${vs.index}
                ${topic.tid}
                ${topic.title}
                ${topic.renshu}
                ${DateUtil.getString(topic.tdate)}
                ${topic.uname}
                删除
                查看

insert.html

数据库的操作

注意：时间是timstamp类型（精确到时分秒），主键一定要自增，不然添加的时候会出现麻烦，你能知道自己要添加的主键吗，不看数据库你能知道你主键添加到第几了吗，最主要是也不能写null来添加主键，因为主键不为null（我的测试不成功，所以写null也不行），总之必须自增！

ALTER DATABASE luntan CHARACTER SET utf8;
alter table user character set utf8; 
alter table liuyan character set utf8; 
alter table topic character set utf8;  
-- 表关系：一个人可以关注多个话题，创建多个话题，因此一对多；一个话题可以有多个留言，每个人可以留言多次
CREATE TABLE user(
	uname VARCHAr(12) PRIMARY KEY, -- 用户名
	upwd VARCHAr(12) not null -- 密码
);
CREATE TABLE topic(
	tid int PRIMARY KEY auto_increment,
	title VARCHAr(12), -- 标题
	tneirong VARCHAr(20), -- 话题内容
	tdate Date not null, -- 话题创建日期
	renshu INT, -- 关注人数
	uname VARCHAr(12) NOT NULL, -- 创建者
    FOREIGN key(uname) REFERENCES user(uname)
);
CREATE TABLE liuyan(
	lid INT PRIMARY KEY,
	ldate DATE not null, -- 留言的时间
	support int, -- 支持的人数
    oppose int, -- 反对的人数
	lneirong VARCHAr(50), -- 留言的内容
	tid INT,
	uname VARCHAr(12) NOT NULL, -- 一对一，每个留言一定要有uname，因此不为空 
	FOREIGN key(uname) REFERENCES USER(uname),
	FOREIGN KEY(tid) REFERENCES topic(tid)
);
alter table topic modify tdate timestamp
alter table liuyan modify ldate timestamp

需要的jar包

如果没有，可以从maven仓库里找，比如javax._或者standrad._下面找

2022/4/21 10:36 获取自增键功能的修改

最初的设计

功能：添加话题
功能解释：每当添加一个话题，添加完毕，转到详情页
设计点：添加完毕之后，转到对应的详情页，但是此时不知道获取哪个话题的详情页（因为用户添加话题，不可能会让用户添加话题的id号，因此这里想要在添加后，将id传给下一个action是很困的事情，只能传个session里的用户名，话题内容，话题标题，另外也不可能知道添加话题的id号，除非看数据库）
具体实现：再写个检索方法，添加成功后立刻检索该session存储的用户的所有话题，在写sql语句的时候，进行了检索，排序，截取操作（类似的功能解决，比如排除添加重复话题，也可以用sql解决，方便快捷代码量少）
局限性：数据库中的用户表与话题表必须有关系，当用户是管理员的时候，与话题表没有关系，当多个管理员并发进行添加操作的时候，即使通过检索数据库截取操作等等也无法获取当前管理员所添加的话题，因为是并发。

select tid from topic order by tid desc limit 1

改进的设计

PreparedStatement里有个参数，叫autoGenereatedKey（大概张这个样子），如

 @Test
    public void test07() throws Exception {
           Class.forName("com.mysql.jdbc.Driver");
           Connection connection=DriverManager.getConnection("","","");
           //设置获取1，不设置获取2
           PreparedStatement preparedStatement = connection.prepareStatement("", Statement.RETURN_GENERATED_KEYS);
           preparedStatement.executeUpdate();
           //获取自增主键
           ResultSet resultSet = preparedStatement.getGeneratedKeys();
    }

Pic：
通过获取自增的主键（1），即省去了getTid方法，可以添加新话题的时候，返回自增主键的id，不必再检索该用户所有话题，倒序截取第一个话题的id了。

${liuyan.uname}	${DateUtil.getString(liuyan.ldate)}	赞:${liuyan.support}	踩:${liuyan.oppose}
${liuyan.lneirong}

添加话题
顺序	编号	标题	关注	时间	作者	操作	查看详情
${vs.index}	${topic.tid}	${topic.title}	${topic.renshu}	${DateUtil.getString(topic.tdate)}	${topic.uname}	删除	查看

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