Java web+MySQL编写简易候选人投票（完整代码）

亦凉 2022-10-26 04:00 62阅读 0赞

# Java web+MySQL编写简易候选人投票（完整代码） #

代码实现效果，自己选的图片太大了，没有做更改，将就看就行  
项目用到的三个jar包自己导入就行

![页面效果][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDczNTAxOA_size_16_color_FFFFFF_t_70]  
代码结构如下图  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDczNTAxOA_size_16_color_FFFFFF_t_70 1]

Candidate中的代码

public class Candidate { 
        private int id;
        private String name;
        private String photoUrl;
        private  int votes;
    
        public int getId(){ 
            return  id;
        }
        public void setId(int id){ 
            this.id = id;
        }
        public String getName(){ 
            return name;
        }
        public void setName(String name){ 
            this.name = name;
        }
        public String getPhotoUrl(){ 
            return photoUrl;
        }
    
        public void setPhotoUrl(String photoUrl){ 
            this.photoUrl = photoUrl;
        }
        public int getVotes(){ 
            return votes;
        }
        public void setVotes(int votes){ 
            this.votes = votes;
        }
    
    }

AddCandidatePageServlet

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 java.io.IOException;
    import java.io.PrintWriter;
    
    @WebServlet("/admin/addcan")
    public class AddCandidatePageServlet extends HttpServlet { 
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            resp.setContentType("text/html;charset=utf8");
            PrintWriter pw = resp.getWriter();
            pw.println("<html><head><title>添加候选人</title></head>");
            pw.println("<body>");
            pw.println("<form action='add' method = 'POST' enctype='multipart/form-data'>");
            pw.println("名字: <input type='text' name='username'><br>");
            pw.println("照片:<input type='file' name = 'img'><br>");
            pw.println("<input type='submit' value = '提交'>");
            pw.println("</form>");
            pw.println("</body></html>");
        }
    }

AddCandidateServlet

@WebServlet("/admin/add")
    public class AddCandidateServlet extends HttpServlet { 
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            //判断上传的文件是否以多段数据进行提交的
            if (ServletFileUpload.isMultipartContent(req)) { 
                //创建FileItemFactory工厂类的示例
                FileItemFactory diskFileItemFactory = new DiskFileItemFactory();
                //创建解析数据所使用的工具类：ServletFileUpload
                ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
                //获取文件存储的绝对路径
                String path = getServletConfig().getServletContext().getRealPath("/")+ "photos\\";
                //解析数据
                try { 
                    String username = null;
                    String img = null;
                    List<FileItem> list = servletFileUpload.parseRequest(req);
                    for (FileItem fileItem : list) { 
                        if (fileItem.isFormField()) { 
                            username = fileItem.getString("UTF-8");
                        } else { 
                            //获取图片的名字
                            img = fileItem.getName();
                            //将文件写入指定的文件夹之中
                            fileItem.write(new File(path + img));
                        }
                    }
                    //将文件名存入数据库
    
                    Candidate candidate = new Candidate();
                    candidate.setName(username);
                    candidate.setPhotoUrl(img);
                    CandidateDao candidateDao = new CandidateDao();
                    candidateDao.add(candidate);
                    System.out.println("存入成功");
                } catch (Exception e) { 
                    e.printStackTrace();
    
                }
            }
            resp.sendRedirect("manage");
        }
    }

DeleteCandidateServlet

@WebServlet("/admin/delete")
    public class DeleteCandidateServlet extends HttpServlet { 
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            req.setCharacterEncoding("utf-8");
            String id = req.getParameter("id");
            Candidate candidate=new Candidate();
            CandidateDao candidateDao=new CandidateDao();
            candidateDao.delete( Integer.parseInt(id));
            resp.sendRedirect("manage");
        }
    }

ManageCandidateServlet

@WebServlet("/admin/manage")
    public class ManageCandidateServlet extends HttpServlet { 
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            resp.setCharacterEncoding("utf-8");
            resp.setContentType("text/html;utf-8");
    // 获取数据
            CandidateDao candidateDao=new CandidateDao();
            ArrayList<Candidate> candidates= (ArrayList<Candidate>) candidateDao.candidateList();
    
    // 获取笔
            PrintWriter pw=resp.getWriter();
    
    // 编号
            int count=1;
            pw.print("<!DOCTYPE html><html><head> <meta charset='UTF-8'><title>管理列表</title></head><body>");
            pw.print("<div><a href='http://localhost:8080/exercise2_vote_war_exploded/admin/addcan'>添加新用户</a></div>");
            pw.print("<table border='1'>");
            pw.print("<tr><td>排名</td> <td>名字</td> <td>ID</td> <td>照片</td><td>票数</td><td>修改</td><td>删除</td></tr>");
            if (candidates!=null){ 
                for (Candidate person:candidates){ 
    
                    pw.print("<tr>");
                    pw.print("<td>"+count+"</td>");
                    pw.print("<td>"+person.getName()+"</td>");
                    pw.print("<td>"+person.getId()+"</td>");
                    pw.print("<td><img src='http://localhost:8080/exercise2_vote_war_exploded/photos/"+person.getPhotoUrl()+"'></td>");
                    pw.print("<td>"+person.getVotes()+"</td>");
                    pw.print("<td><a href='http://localhost:8080/exercise2_vote_war_exploded/admin/modify?id="+person.getId()+"'>修改</a></td>");
                    pw.print("<td><a href='http://localhost:8080/exercise2_vote_war_exploded/admin/delete?id="+person.getId()+"'>删除</a></td>");
                    pw.print("</tr>");
                    count++;
                }
            }
            pw.print("</table>");
            pw.print("<a href='http://localhost:8080/exercise2_vote_war_exploded/index'>用户列表</a>");
            pw.print("</body></html>");
        }
    }

ModifyCandidatePageServlet

@WebServlet("/admin/modify")
    public class ModifyCandidatePageServlet extends HttpServlet { 
        // 修改候选人信息
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            resp.setContentType("text/html;utf-8");
            resp.setCharacterEncoding("utf-8");
    //获取初始候选人数据
            String id1= req.getParameter("id");
            int id=Integer.parseInt(id1);
            CandidateDao candidateDao=new CandidateDao();
            Candidate candidate= candidateDao.select(id);
    // 渲染成表单数据
            PrintWriter pw=resp.getWriter();
            pw.print("<!DOCTYPE html><html><head> <meta charset='UTF-8'><title>修改候选人信息</title></head><body>");
            pw.print("<form action = 'mod' method = 'POST' enctype='multipart/form-data'>");
            pw.print("id : <input type='text' name='id' value='"+candidate.getId()+"'></br>");
            pw.print("name : <input type='text' name='username' value='"+candidate.getName()+"'></br>");
            pw.print("photo : <input type='file' name='photo' value='"+candidate.getPhotoUrl()+"'></br>");
            pw.print("<input type='submit' value='提交'></br>");
            pw.print("</form>");
            pw.print("</body></html>");
        }
    }

ModifyCandidateServlet

@WebServlet("/admin/mod")
    public class ModifyCandidateServlet extends HttpServlet { 
    
        @Override
        protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            if (ServletFileUpload.isMultipartContent(req)) { 
                System.out.println("qwertyy");
                //创建FileItemFactory工厂类的示例
                FileItemFactory diskFileItemFactory = new DiskFileItemFactory();
                //创建解析数据所使用的工具类：ServletFileUpload
                ServletFileUpload servletFileUpload = new ServletFileUpload(diskFileItemFactory);
                //
                String path = getServletConfig().getServletContext().getRealPath("/") + "photos\\";
                //解析数据
                try { 
                    String username = null;
                    String img = null;
                    String id = null;
                    List<FileItem> list = servletFileUpload.parseRequest(req);
    
                    for (FileItem fileItem : list) { 
                        System.out.println(fileItem);
                        if (fileItem.isFormField()) { 
                            if ("username".equals(fileItem.getFieldName())){ 
    
                                username = fileItem.getString("UTF-8");
                                System.out.println(username+"获取用户姓名");
                            }
                            if ("id".equals(fileItem.getFieldName())){ 
                                System.out.println("id的获取"+fileItem.getString());
                                id = fileItem.getString("UTF-8");
                            }
    
                        }
                        else { 
                            //获取图片的名字
                            img = fileItem.getName();
    // id=req.getParameter("id");
                            //将文件写入指定文件夹之中
                            fileItem.write(new File(path + img));
                        }
                    }
                    //将文件名存入数据库
                    Candidate candidate=  new Candidate();
                    candidate.setName(username);
                    candidate.setPhotoUrl(img);
                    candidate.setId(Integer.parseInt(id));
                    CandidateDao candidateDao=new CandidateDao();
                    candidateDao.update(candidate);
                    System.out.println("更新成功");
    
                } catch (Exception e) { 
                    e.printStackTrace();
                }
                resp.sendRedirect("manage");
            }else{ 
                System.out.println("错误！");
            }
        }
    }

ListCandidateServlet

@WebServlet("/index")
    public class ListCandidateServlet extends HttpServlet { 
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
            //先获取数据
            CandidateDao candidateDao=new CandidateDao();
            ArrayList<Candidate> candidates= (ArrayList<Candidate>) candidateDao.candidateList();
    
    // 排名编号 ---查询到的数据以投票数降序排序
            int count=1;
            resp.setCharacterEncoding("utf-8");
            resp.setContentType("text/html;utf-8");
            PrintWriter printWriter=resp.getWriter();
            printWriter.print("<!DOCTYPE html><html><head> <meta charset='UTF-8'><title>简易投票系统</title></head><body>");
            printWriter.print("<table border='1'>");
            printWriter.print("<tr> <td>排名</td> <td>名字</td> <td>ID</td> <td>照片</td><td>票数</td><td>投票</td></tr>");
            if (candidates!=null){ 
                for (Candidate person:candidates){ 
                    printWriter.print("<tr>");
                    printWriter.println("<td>" + count + "</td>");
                    printWriter.println("<td>" + person.getName() + "</td>");
                    printWriter.println("<td>" + person.getId() + "</td>");
                    //待修改
    
    
                    printWriter.println("<td><img src='photos/" + person.getPhotoUrl() + "'></td>");
                    printWriter.println("<td>" + person.getVotes() + "</td>");
                    printWriter.println("<td><a href = '/exercise2_vote_war_exploded/vote?id="+ person.getId()+ "'>投票</a></td>");
                    printWriter.println("</tr>");
    
                    count++;
                }
            }
    
            printWriter.println("</table>");
            printWriter.println("<a href='http://localhost:8080/exercise2_vote_war_exploded/admin/manage'>管理候选人</a>");
            printWriter.println("</body></html>");
        }
    }

VoteServlet

@WebServlet("/vote")
    public class VoteServlet extends HttpServlet { 
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
    
            req.setCharacterEncoding("utf-8");
            String id1=req.getParameter("id");
    
            if (id1!=null){ 
                System.out.println(id1);
                int id=Integer.parseInt(id1);
                CandidateDao candidateDao=new CandidateDao();
                candidateDao.addVote(id);
                req.getRequestDispatcher("index").forward(req,resp);
            }
            System.out.println("未获取到id");
        }
    }

dao层里面的CandidateDao

public class CandidateDao implements Dao { 
    
        Connection connection;
        { 
            try{ 
                connection = JdbcUtil.getConnection();
            } catch (SQLException e) { 
                e.printStackTrace();
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
        }
        public void add(Candidate candidate) { 
            String sql="insert into table_candidate values(null,?,?,?)";
            try(PreparedStatement ps=connection.prepareStatement(sql)){ 
                ps.setString(1,candidate.getName());
                ps.setString(2,candidate.getPhotoUrl());
                ps.setInt(3,candidate.getVotes());
                ps.execute();
                System.out.println("向数据库中插入一条记录");
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    
        @Override
        public void update(Candidate candidate) { 
            String sql="update table_candidate set name= ?,photoUrl = ? where id=?";
            try(PreparedStatement ps=connection.prepareStatement(sql)){ 
                ps.setInt(3,candidate.getId());
                ps.setString(1,candidate.getName());
                ps.setString(2,candidate.getPhotoUrl());
    //ps.setInt(3,candidate.getVotes());
                ps.execute();
                System.out.println("更新了数据库中这条id为："+candidate.getId()+"的记录");
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    
        @Override
        public void delete(int id) { 
            String sql="delete from table_candidate where id=?";
            try (PreparedStatement ps=connection.prepareStatement(sql);){ 
                ps.setInt(1,id);
                ps.execute();
                System.out.println("删除了数据库中这条id为："+id+"的记录");
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    
        @Override
        public Candidate select(int id) { 
            Candidate candidate=null;
            String sql=" select * from table_candidate where id= ?";
            try(   PreparedStatement ps=connection.prepareStatement(sql);) { 
                ps.setInt(1,id);
    
                ResultSet rs= ps.executeQuery();
                if (rs.next()){ 
    
                    String name=rs.getString(2);
                    String photoUrl=rs.getString(3);
                    int votes=rs.getInt(4);
                    candidate=new Candidate();
    
                    candidate.setId(id);
                    candidate.setName(name);
                    candidate.setPhotoUrl(photoUrl);
                    candidate.setVotes(votes);
                    System.out.println("查询单条记录成功");
                }
            } catch (SQLException e) { 
                e.printStackTrace();
            }
            return candidate;
        }
    
        @Override
        public List<Candidate> candidateList() { 
            // 直接调用有参获取候选人方法，只不过参数是0-最后
            return orderPageList(0,10000);
        }
    
        @Override
        public List<Candidate> orderPageList(int start, int count) { 
            // 存放获取候选人列表
            ArrayList<Candidate> candidates=new ArrayList<Candidate>();
            String sql="select * from table_candidate order by votes desc limit ? , ? ";
            try (PreparedStatement ps=connection.prepareStatement(sql);)  { 
                ps.setInt(1,start);
                ps.setInt(2,count);
                ResultSet rs=ps.executeQuery();
                while (rs.next()){ 
                    Candidate candidate=new Candidate();
                    int id=rs.getInt(1);
                    String name=rs.getString(2);
                    String photoUrl=rs.getString(3);
                    int votes=rs.getInt(4);
                    candidate.setId(id);
                    candidate.setName(name);
                    candidate.setPhotoUrl(photoUrl);
                    candidate.setVotes(votes);
                    candidates.add(candidate);
    // System.out.println("查询候选人信息成功");
                }
            } catch (SQLException e) { 
                e.printStackTrace();
            }
    
            return candidates;
        }
        public  void  addVote(int id){ 
            String sql="update table_candidate set votes=votes+1 where id=?";
            try (  PreparedStatement ps=connection.prepareStatement(sql);){ 
                ps.setInt(1,id);
                ps.execute();
    // System.out.println("id为："+id+"的候选者投票数加一");
            } catch (SQLException e) { 
                e.printStackTrace();
            }
        }
    }

Dao

public interface Dao { 
        public void add(Candidate candidate);
        public  void update(Candidate candidate);
        public  void delete (int id);
        //获取单个候选人
        public Candidate select(int id);
        //候选人列表
        public List<Candidate> candidateList();
        //分页查询候选人
        public List<Candidate> orderPageList(int start,int count);
    }

JdbcUti

public class JdbcUtil { 
        private static Connection connection;
        public  static  Connection getConnection() throws ClassNotFoundException, SQLException{ 
            Class.forName("com.mysql.cj.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb?useSSL=false&serverTimezone=UTC", "root", "自己数据的密码");
            return connection;
        }
        //关闭连接
        public static void closeResourse(Connection connection, PreparedStatement preparedStatement){ 
            if(preparedStatement!=null){ 
                try{ 
                    preparedStatement.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
            if (connection!=null){ 
                try{ 
                    connection.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
        }
    
        public static void closeResourse(Connection connection, PreparedStatement preparedStatement, ResultSet rs){ 
            if(preparedStatement!=null){ 
                try{ 
                    preparedStatement.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
            if(connection !=null){ 
                try{ 
                    connection.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
            if (rs!=null){ 
                try{ 
                    rs.close();
                } catch (SQLException e) { 
                    e.printStackTrace();
                }
            }
        }
    }

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