• 选课系统(后端)


    package com.dao;
    
    import java.sql.Statement;
    import java.util.ArrayList;
    import java.util.List;
    import java.sql.Connection;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    
    import com.entity.Message1;
    import com.entity.Message2;
    import com.entity.Message3;
    import com.util.DBUtil;
    
    public class MessageDao {
        //登录
        public int login(String username, String password,String shenfen) {
            String sql=null;
            if(shenfen.equals("student")) {
                sql="select * from d2 where num='"+username+"'and password='"+password+"'";
            }else if(shenfen.equals("teacher")) {
                sql="select * from d1 where num='"+username+"'and password='"+password+"'";
            }else if(shenfen.equals("manage")) {
                sql="select * from d4 where username='"+username+"'and password='"+password+"'";
            }
             Connection conn=DBUtil.getConn();
             Statement st=null;
             ResultSet rs=null;
             int row=0;
             try {
                 st=conn.createStatement();
                 rs=st.executeQuery(sql);
                 if (rs.next()) {
                    row=1;
                }else {
                    row=0;
                }
            } catch (Exception e) {
                // TODO: handle exception
            }
            return row;
        }
       //添加
        public boolean add1(Message1 message) {
            String sql = "insert into d1(num,tname,tsex,txueyuan,tzhicheng,password)"+"values('" + message.getNum() + "','"
                    + message.getTname() + "','" + message.getTsex() + "','" + message.getTxueyuan() + "','"
                    + message.getTzhicheng() + "','"+message.getPassword()+"')";
            // 创建数据库链接
            Connection conn = DBUtil.getConn();
            Statement state = null;
            boolean f = false;
            int a = 0;
    
            try {
                state = conn.createStatement();
                state.executeUpdate(sql);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                // 关闭连接
                DBUtil.close(state, conn);
            }
    
            if (a > 0) {
                f = true;
            }
            return f;
        }
        public boolean add2(Message2 message) {
            String sql = "insert into d2(num,sname,ssex,sclass,smajor,password)"+"values('" + message.getNum() + "','"
                    + message.getSname() + "','" + message.getSsex() + "','" + message.getSclass() + "','"
                    + message.getSmajor() + "','"+message.getPassword()+"')";
            // 创建数据库链接
            Connection conn = DBUtil.getConn();
            Statement state = null;
            boolean f = false;
            int a = 0;
    
            try {
                state = conn.createStatement();
                state.executeUpdate(sql);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                // 关闭连接
                DBUtil.close(state, conn);
            }
    
            if (a > 0) {
                f = true;
            }
            return f;
        }
        public boolean add3(Message3 message) {
            String sql = "insert into d3(cnum,cname,cpnum,cteacher)"+"values('" + message.getCnum() + "','"
                    + message.getCname() + "','" + message.getCpnum() + "','" + message.getCteacher() + "')";
            // 创建数据库链接
            Connection conn = DBUtil.getConn();
            Statement state = null;
            boolean f = false;
            int a = 0;
    
            try {
                state = conn.createStatement();
                state.executeUpdate(sql);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                // 关闭连接
                DBUtil.close(state, conn);
            }
    
            if (a > 0) {
                f = true;
            }
            return f;
        }
         public static boolean num1(String num) {
                boolean flag = false;
                String sql = "select * from d1 where num = '" + num + "'";
                Connection conn = DBUtil.getConn();
                Statement state = null;
                ResultSet rs = null;
                
                try {
                    state = conn.createStatement();
                    rs = state.executeQuery(sql);
                    while (rs.next()) {
                        flag = true;
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                } finally {
                    DBUtil.close(rs, state, conn);
                }
                return flag;
            }
         public static boolean num2(String num) {
                boolean flag = false;
                String sql = "select * from d2 where num = '" + num + "'";
                Connection conn = DBUtil.getConn();
                Statement state = null;
                ResultSet rs = null;
                
                try {
                    state = conn.createStatement();
                    rs = state.executeQuery(sql);
                    while (rs.next()) {
                        flag = true;
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                } finally {
                    DBUtil.close(rs, state, conn);
                }
                return flag;
            }
         public static boolean num3(String cnum) {
                boolean flag = false;
                String sql = "select * from d3 where cnum = '" + cnum + "'";
                Connection conn = DBUtil.getConn();
                Statement state = null;
                ResultSet rs = null;
                
                try {
                    state = conn.createStatement();
                    rs = state.executeQuery(sql);
                    while (rs.next()) {
                        flag = true;
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                } finally {
                    DBUtil.close(rs, state, conn);
                }
                return flag;
            }
        //查询
         public  Message1 search(String name) {
                String sql = "select * from d1 where name = '" + name + "'";       
                Connection conn = DBUtil.getConn();
                Statement state = null;
                ResultSet rs = null;
                Message1 bean=null;
                try {
                    state = conn.createStatement();
                    rs = state.executeQuery(sql);
                    while (rs.next()) {
                        int id2=rs.getInt("id");
                        String name2 = rs.getString("name");
                        String sex2 = rs.getString("sex");
                        String nation2 = rs.getString("nation");
                        String date2 = rs.getString("date");
                        String age2=rs.getString("age");
                        String politics2=rs.getString("politics");
                        /*bean = new Message1(id2,name2,sex2,nation2,date2,age2,politics2);*/
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                } finally {
                    DBUtil.close(rs, state, conn);
                }       
                return bean;
            }
         //删除
             public boolean delete(String name){
                    String sql="delete from d1 where name='" + name + "'";
                    Connection conn = DBUtil.getConn();
                    Statement state = null;
                    int a = 0;
                    boolean f = false;
                    try {
                        state = conn.createStatement();
                        a = state.executeUpdate(sql);
                    } catch (SQLException e) {
                        e.printStackTrace();
                    } finally {
                        DBUtil.close(state, conn);
                    }
                    
                    if (a > 0) {
                        f = true;
                    }
                    return f;
                }
            //通过姓名查找
             public static Message1 getMessageBynum1(String num) {
                    String sql = "select * from d1 where num ='" + num + "'";
                    Connection conn = DBUtil.getConn();
                    Statement state = null;
                    ResultSet rs = null;
                    Message1 message = null;            
                    try {
                        state = conn.createStatement();
                        rs = state.executeQuery(sql);
                        while (rs.next()) {
                            String num1 = rs.getString("num");
                            String tname = rs.getString("tname");
                            String tsex = rs.getString("tsex");
                            String txueyuan=rs.getString("txueyuan");
                            String tzhicheng=rs.getString("tzhicheng");      
                            String password=rs.getString("password");    
                            message = new Message1(num1,tname,tsex,txueyuan,tzhicheng,password);                 
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally {
                        DBUtil.close(rs, state, conn);
                    }
                    
                    return message;
                }
             public static Message2 getMessageBynum2(String num) {
                    String sql = "select * from d2 where num ='" + num + "'";
                    Connection conn = DBUtil.getConn();
                    Statement state = null;
                    ResultSet rs = null;
                    Message2 message = null;            
                    try {
                        state = conn.createStatement();
                        rs = state.executeQuery(sql);
                        while (rs.next()) {
                            String num1 = rs.getString("num");
                            String tname = rs.getString("sname");
                            String tsex = rs.getString("ssex");
                            String txueyuan=rs.getString("sclass");
                            String tzhicheng=rs.getString("smajor");      
                            String password=rs.getString("password");    
                            message = new Message2(num1,tname,tsex,txueyuan,tzhicheng,password);                 
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally {
                        DBUtil.close(rs, state, conn);
                    }
                    
                    return message;
                }
             public static String getMessageBynum3(String num) {
                    String sql = "select * from d1 where num ='" + num + "'";
                    Connection conn = DBUtil.getConn();
                    Statement state = null;
                    ResultSet rs = null;
                    Message1 message = null;            
                    try {
                        state = conn.createStatement();
                        rs = state.executeQuery(sql);
                        while (rs.next()) {
                            String num1 = rs.getString("num");
                            String tname = rs.getString("tname");
                            String tsex = rs.getString("tsex");
                            String txueyuan=rs.getString("txueyuan");
                            String tzhicheng=rs.getString("tzhicheng");      
                            String password=rs.getString("password");    
                            message = new Message1(num1,tname,tsex,txueyuan,tzhicheng,password);                 
                        }
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally {
                        DBUtil.close(rs, state, conn);
                    }
                    
                    return message.getTname();
                }
             //修改
             public static boolean update12(Message1 message,String name) {
                    
                 String sql = "update d1 set num='" + message.getNum() + "', tname='" + message.getTname()+"',tsex='"+message.getTsex()+"',txueyuan='"+message.getTxueyuan()+"', tzhicheng='" + message.getTzhicheng() + "', password='" + message.getPassword() + "'where num ='" + name + "'";
                    Connection conn = DBUtil.getConn();
                    Statement state = null;
                    boolean f = false;
                    int a = 0;
                    
                    try {
                        state = conn.createStatement();
                        a = state.executeUpdate(sql);
                    } catch (SQLException e) {
                        e.printStackTrace();
                    } finally {
                        DBUtil.close(state, conn);
                    }
                    
                    if (a > 0) {
                        f = true;
                    }
                    return f;
                }
             public static boolean update22(Message2 message,String name) {
                    
                 String sql = "update d2 set num='" + message.getNum() + "', sname='" + message.getSname()+"',ssex='"+message.getSsex()+"',Sclass='"+message.getSclass()+"', Smajor='" + message.getSmajor() + "', password='" + message.getPassword() + "'where num ='" + name + "'";
                    Connection conn = DBUtil.getConn();
                    Statement state = null;
                    boolean f = false;
                    int a = 0;
                    
                    try {
                        state = conn.createStatement();
                        a = state.executeUpdate(sql);
                    } catch (SQLException e) {
                        e.printStackTrace();
                    } finally {
                        DBUtil.close(state, conn);
                    }
                    
                    if (a > 0) {
                        f = true;
                    }
                    return f;
                }
             //显示全部
             public List<Message3> list()
                {
                    String sql = "select * from d3";
                    List<Message3> list = new ArrayList<>();
                    Connection conn = DBUtil.getConn();
                    Statement state = null;
                    ResultSet rs = null;            
                    try {
                        state = conn.createStatement();
                        rs = state.executeQuery(sql);
                        while (rs.next()) {
                            Message3 bean = null;
                            String cnum=rs.getString("cnum");
                            String cname = rs.getString("cname");
                            String cpnum = rs.getString("cpnum");
                            String cteacher = rs.getString("cteacher");                
                            bean =new Message3(cnum,cname,cpnum,cteacher);                        
                            list.add(bean);
                        }
                    } catch (SQLException e) {
                        e.printStackTrace();
                    } finally {
                        DBUtil.close(rs, state, conn);
                    }
                    
                    return list;
                }    
             
    }
    package com.entity;
    //tnum tname tsex txueyaun tzhicheng
    public class Message1 {
    private String num;
    private String tname;
    private String tsex;
    private String txueyuan;
    private String tzhicheng;
    private String password;
    public String getNum() {
        return num;
    }
    public void setNum(String num) {
        this.num = num;
    }
    public String getTname() {
        return tname;
    }
    public void setTname(String tname) {
        this.tname = tname;
    }
    public String getTsex() {
        return tsex;
    }
    public void setTsex(String tsex) {
        this.tsex = tsex;
    }
    public String getTxueyuan() {
        return txueyuan;
    }
    public void setTxueyuan(String txueyuan) {
        this.txueyuan = txueyuan;
    }
    public String getTzhicheng() {
        return tzhicheng;
    }
    public void setTzhicheng(String tzhicheng) {
        this.tzhicheng = tzhicheng;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public Message1(String num, String tname, String tsex, String txueyuan, String tzhicheng, String password) {
        super();
        this.num = num;
        this.tname = tname;
        this.tsex = tsex;
        this.txueyuan = txueyuan;
        this.tzhicheng = tzhicheng;
        this.password = password;
    }
    public Message1() {
        super();
        // TODO 自动生成的构造函数存根
    }
    
    }
    package com.entity;
    
    public class Message2 {
        //num sname ssex sclass smajor
        private String num;
        private String sname;
        private String ssex;
        private String sclass;
        private String smajor;
        private String password;
        public String getNum() {
            return num;
        }
        public void setNum(String num) {
            this.num = num;
        }
        public String getSname() {
            return sname;
        }
        public void setSname(String sname) {
            this.sname = sname;
        }
        public String getSsex() {
            return ssex;
        }
        public void setSsex(String ssex) {
            this.ssex = ssex;
        }
        public String getSclass() {
            return sclass;
        }
        public void setSclass(String sclass) {
            this.sclass = sclass;
        }
        public String getSmajor() {
            return smajor;
        }
        public void setSmajor(String smajor) {
            this.smajor = smajor;
        }
        public String getPassword() {
            return password;
        }
        public void setPassword(String password) {
            this.password = password;
        }
        public Message2(String num, String sname, String ssex, String sclass, String smajor, String password) {
            super();
            this.num = num;
            this.sname = sname;
            this.ssex = ssex;
            this.sclass = sclass;
            this.smajor = smajor;
            this.password = password;
        }
    }
    package com.entity;
    
    public class Message3 {
        public String cnum;
        public String cname;
        public String cpnum;
        public String cteacher;
        public String getCnum() {
            return cnum;
        }
        public void setCnum(String cnum) {
            this.cnum = cnum;
        }
        public String getCname() {
            return cname;
        }
        public void setCname(String cname) {
            this.cname = cname;
        }
        public String getCpnum() {
            return cpnum;
        }
        public void setCpnum(String cpnum) {
            this.cpnum = cpnum;
        }
        public String getCteacher() {
            return cteacher;
        }
        public void setCteacher(String cteacher) {
            this.cteacher = cteacher;
        }
        public Message3(String cnum, String cname, String cpnum, String cteacher) {
            super();
            this.cnum = cnum;
            this.cname = cname;
            this.cpnum = cpnum;
            this.cteacher = cteacher;
        }
        
    }
    package com.service;
    
    import java.util.List;
    
    import com.dao.MessageDao;
    import com.entity.Message1;
    import com.entity.Message2;
    import com.entity.Message3;
    
    //服务层
    public class MessageService {
    
        MessageDao mDao = new MessageDao();
        //登录
        public int login(String username,String password,String shenfen) {
            return mDao.login(username,password,shenfen);
        }
        //添加
        public boolean add1(Message1 message) {
            boolean f = false;
            if(!mDao.num1(message.getNum())) {
                mDao.add1(message);
                f = true;
            }
            return f;
        }
        public boolean add2(Message2 message) {
            boolean f = false;
            if(!mDao.num2(message.getNum())) {
                mDao.add2(message);
                f = true;
            }
            return f;
        }
        public boolean add3(Message3 message) {
            boolean f = false;
            if(!mDao.num3(message.getCnum())) {
                mDao.add3(message);
                f = true;
            }
            return f;
        }
        //查找
        public Message1 search(String name) {
            return mDao.search(name);
        }
        //删除
        public boolean delete(String name) {
            
               mDao.delete(name);
                   return true;
                }
        public Message1 getMessageBynum(String num)
        {
            return mDao.getMessageBynum1(num);
        }
        //修改
        public  void update(Message1 message,String num) {
            mDao.update12(message,num);
        }
        //显示所有
        public List<Message3> list()
        {
            return mDao.list();
        }
    }
    package com.servlet;
    
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.dao.MessageDao;
    import com.entity.Message1;
    import com.entity.Message2;
    import com.entity.Message3;
    import com.service.MessageService;
    
    @WebServlet("/MessageServlet")
    public class MessageServlet extends HttpServlet {
        static String wen=null; 
        static String mo=null;
        private static final long serialVersionUID = 1L;
    
        MessageService service = new MessageService();
        
        /**
         * 方法选择
         */
        protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            req.setCharacterEncoding("utf-8");
            String method = req.getParameter("method");
            
            if ("add1".equals(method)) {
                add1(req, resp);
            }else if ("login".contentEquals(method)) {
                login(req, resp);
            }else if ("add2".equals(method)) {
                add2(req, resp);
            }else if ("add3".equals(method)) {
                add3(req, resp);
            }else if ("update11".equals(method)) {
                update11(req, resp);
            }else if ("update12".equals(method)) {
                update12(req, resp);
            }else if ("update21".equals(method)) {
                update21(req, resp);
            }else if ("update22".equals(method)) {
                update22(req, resp);
            }else if ("list".equals(method)) {
                list(req, resp);
            }
        }
      //登录
          private void login(HttpServletRequest req,HttpServletResponse resp) throws IOException, ServletException {
              req.setCharacterEncoding("utf-8");
              String username=req.getParameter("username");
              String password=req.getParameter("password");
              String shenfen=req.getParameter("shenfen");
              int message=service.login(username,password,shenfen);
              if(message == 0) {
                  req.setAttribute("message", "帐号或密码错误!");
                  req.getRequestDispatcher("login.jsp").forward(req,resp);
                  } else {
                      Cookie cookie=new Cookie("username", username);
                    cookie.setPath("/");
                    cookie.setMaxAge(60*60*24);
                    resp.addCookie(cookie);
                         req.setAttribute("message", "登陆成功");
                         req.getRequestDispatcher(shenfen+".jsp").forward(req,resp);
                  }
          }
     //添加
        private void add1(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
            req.setCharacterEncoding("utf-8");
            //获取数据num tname tsex txueyaun tzhicheng
            String num = req.getParameter("num");
            String tname = req.getParameter("tname");
            String tsex = req.getParameter("tsex");
            String txueyuan = req.getParameter("txueyuan");
            String tzhicheng = req.getParameter("tzhicheng");
            String password = req.getParameter("password");
            Message1 message = new Message1(num,tname,tsex,txueyuan,tzhicheng,password);
            
            //添加后消息显示
            if(service.add1(message)) {
                req.setAttribute("message", "添加成功");
                req.getRequestDispatcher("manage.jsp").forward(req,resp);
            } else {
                req.setAttribute("message", "工号重复,请重新录入");
                req.getRequestDispatcher("add1.jsp").forward(req,resp);
            }
        }
        private void add2(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
            req.setCharacterEncoding("utf-8");
            //snum sname ssex sclass smajor
            String num = req.getParameter("num");
            String sname = req.getParameter("sname");
            String ssex = req.getParameter("ssex");
            String sclass = req.getParameter("sclass");
            String smajor = req.getParameter("smajor");
            String password = req.getParameter("password");
            Message2 message = new Message2(num,sname,ssex,sclass,smajor,password);
            
            //添加后消息显示
            if(service.add2(message)) {
                req.setAttribute("message", "添加成功");
                req.getRequestDispatcher("manage.jsp").forward(req,resp);
            } else {
                req.setAttribute("message", "学号重复,请重新录入");
                req.getRequestDispatcher("add2.jsp").forward(req,resp);
            }
        }
        private void add3(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
            req.setCharacterEncoding("utf-8");
            //snum sname ssex sclass smajor
            String cnum = req.getParameter("cnum");
            String cname = req.getParameter("cname");
            String cpnum = req.getParameter("cpnum");
            String cteacher = req.getParameter("cteacher");
            Message3 message = new Message3(cnum,cname,cpnum,cteacher);
            
            //添加后消息显示
            if(service.add3(message)) {
                req.setAttribute("message", "添加成功");
                req.getRequestDispatcher("teacher.jsp").forward(req,resp);
            } else {
                req.setAttribute("message", "课程编号重复,请重新录入");
                req.getRequestDispatcher("add3.jsp").forward(req,resp);
            }
        }
        //查询
        private void search(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            String name = req.getParameter("name");       
            Message1 message = service.search(name);
            if(message == null) {
                req.setAttribute("message", "查无此用户!");
                req.getRequestDispatcher("search.jsp").forward(req,resp);
            } else {
                req.setAttribute("message", message);
                req.getRequestDispatcher("search1.jsp").forward(req,resp);
            }
        }
        private void search1(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            String name = req.getParameter("name");       
            Message1 message = service.search(name);
            if(message == null) {
                req.setAttribute("message", "查无此用户!");
                req.getRequestDispatcher("search.jsp").forward(req,resp);
            } else {
                req.setAttribute("message", message);
                req.getRequestDispatcher("search2.jsp").forward(req,resp);
            }
        }
        
        //删除
        private void delete(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            
               //String name=req.getParameter("name");
               //if(MessageDao.name(name))        
                service.delete(mo);
                req.setAttribute("message", "删除成功!");
                req.getRequestDispatcher("delete.jsp").forward(req,resp); 
    }  
       //通过姓名查找后删除
       /* private void getMessageByname(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            String name = req.getParameter("name");
            Message1 message = service.getMessageByname(name);
            mo=name;
            if(message==null)
            {
                req.setAttribute("message", "未找到该用户");
                req.getRequestDispatcher("delete.jsp").forward(req, resp);
            }
            else 
            {
                req.setAttribute("message", message);
                req.getRequestDispatcher("delete1.jsp").forward(req,resp);
            }
        }*/
      
        private void update11(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            String num = req.getParameter("num");
            Message1 message = MessageDao.getMessageBynum1(num);
            wen=num;
            if(message==null)
            {
                req.setAttribute("message","未找到该用户");
                req.getRequestDispatcher("teacher.jsp").forward(req, resp);
            }
            else
            {
                req.setAttribute("message",message);
                req.getRequestDispatcher("update12.jsp").forward(req,resp);
            }
        }
        private void update21(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            String num = req.getParameter("num");
            Message2 message = MessageDao.getMessageBynum2(num);
            wen=num;
            if(message==null)
            {
                req.setAttribute("message","未找到该用户");
                req.getRequestDispatcher("update21.jsp").forward(req, resp);
            }
            else
            {
                req.setAttribute("message",message);
                req.getRequestDispatcher("update22.jsp").forward(req,resp);
            }
        }
        //修改
        private void update12(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
             String num3 = req.getParameter("num");
             String tname3 = req.getParameter("tname");
             String tsex3 = req.getParameter("tsex");
             String txueyuan3 = req.getParameter("txueyuan");
             String tzhicheng3 = req.getParameter("tzhicheng");
             String password3 = req.getParameter("password");
             Message1 message = new Message1(num3,tname3,tsex3,txueyuan3,tzhicheng3,password3);
            if(MessageDao.update12(message,wen))
            { 
                req.setAttribute("message","修改成功");
                req.getRequestDispatcher("update11.jsp").forward(req,resp);
            }
            }
        
        private void update22(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
             String num3 = req.getParameter("num");
             String sname3 = req.getParameter("sname");
             String ssex3 = req.getParameter("ssex");
             String sclass3 = req.getParameter("sclass");
             String smajor3 = req.getParameter("smajor");
             String password3 = req.getParameter("password");
             Message2 message = new Message2(num3,sname3,ssex3,sclass3,smajor3,password3);
            if(MessageDao.update22(message,wen))
            { 
                req.setAttribute("message","修改成功");
                req.getRequestDispatcher("update21.jsp").forward(req,resp);
            }
            }
        
        //显示全部
        private void list(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException{
            req.setCharacterEncoding("utf-8");
            
            List<Message3> messages = service.list();
            req.setAttribute("messages", messages);
            req.getRequestDispatcher("allcourse.jsp").forward(req,resp);
        }
    }
    //DBUtil.java
    package com.util;
    
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    
    
    
    public class DBUtil {
        
        public static String db_url = "jdbc:mysql://localhost:3306/select_system?useSSL=false&serverTimezone=GMT";
        public static String db_user = "root";
        public static String db_pass = "0000";
        
        public static Connection getConn () {
            Connection conn = null;
            
            try {
                Class.forName("com.mysql.jdbc.Driver");//加载驱动
                conn = DriverManager.getConnection(db_url, db_user, db_pass);
            } catch (Exception e) {
                e.printStackTrace();
            }
            
            return conn;
        }
        
        /**
         * 关闭连接
         * @param state
         * @param conn
         */
        public static void close (Statement state, Connection conn) {
            if (state != null) {
                try {
                    state.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        
        public static void close (ResultSet rs, Statement state, Connection conn) {
            if (rs != null) {
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            
            if (state != null) {
                try {
                    state.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    
        public static void main(String[] args) throws SQLException {
            Connection conn = getConn();
            PreparedStatement pstmt = null;
            ResultSet rs = null;
            String sql ="select * from d1";
            pstmt = conn.prepareStatement(sql);
            rs = pstmt.executeQuery();
            if(rs.next()){
                System.out.println("空");
            }else{
                System.out.println("不空");
            }
        }
    }
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  • 原文地址:https://www.cnblogs.com/dd110343/p/12151799.html
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