mysql       mysql-connector-java       8.0.21                  javax.servlet       javax.servlet-api       3.0.1       provided                  javax.servlet.jsp       jsp-api       2.2       provided      

SET NAMES utf-8; CREATE DATABASE studentManager; USE studentManager; CREATE TABLE student (   sno INT PRIMARY KEY,   sname VARCHAR(20) NOT NULL,   sex CHAR(4) ,   age INT DEFAULT 20,   phone VARCHAR(30)  );  INSERT INTO student VALUES(1001,'jack','男',23,'13389076524'); INSERT INTO student VALUES(1002,'rose','女',23,'18760987543'); INSERT INTO student VALUES(1003,'tom','男',23,'13389067823'); INSERT INTO student VALUES(1004,'王麻子','男',23,'13560738947'); INSERT INTO student VALUES(1005,'大麻子','男',23,'18899067532');  INSERT INTO student VALUES(1006,'小麻子','男',23,'15678634789'); INSERT INTO student VALUES(1007,'老麻子','男',23,'12199834572'); INSERT INTO student VALUES(1008,'张三','男',23,'15533098843'); INSERT INTO student VALUES(1009,'长萨珊','女',23,'12209835679'); INSERT INTO student VALUES(1010,'李四','女',23,'15509087635');  INSERT INTO student VALUES(1011,'王五','男',23,'15788679043'); INSERT INTO student VALUES(1012,'赵六','女',23,'12489034506'); INSERT INTO student VALUES(1013,'刘二','男',23,'13560596743');  CREATE TABLE login (   uid INT PRIMARY KEY,   pwd VARCHAR(20) NOT NULL, );  INSERT INTO login VALUES(1, '1234'); INSERT INTO login VALUES(2, '2222'); INSERT INTO login VALUES(3, '6688'); 

<%@ page language="java" contentType="text/html; charset=utf-8"  pageEncoding="utf-8"%>                     
     
学生信息管理平台
      
     
         
             用户登录  立即注册         
          
                      
         
                      
                  <%             if(session.getAttribute("loginErrorMessage") != null){                  String loginErrorMessage = (String)session.getAttribute("loginErrorMessage");                 out.print(loginErrorMessage);             }         %>         <%             String register = (String) request.getAttribute("register");             if (register!= null) {                 if (register.equals("reg")) {                     out.println("注册成功, 请登录！");                 }             }         %>     
     
 
   

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>                   
     
学生信息管理平台
     
         
             
用户注册
             
                              
             
                              
                          返回          
     
 
    

<%@ page language="java" contentType="text/html; charset=utf-8"  pageEncoding="utf-8"%> <%@ page import="com.stu.po.Student" %>                 
     
欢迎进入学生信息管理平台
     <%         if(session.getAttribute("login") == null) {             session.setAttribute("loginErrorMessage", "您必须先登录才能访问主页！");             response.sendRedirect("index.jsp");         }     %>     
         添加学生         分页查询         查看所有学生信息         退出登录     
 
   

<%@ page contentType="text/html;charset=UTF-8" language="java" %>                  
     
学生信息管理平台
     
         
             
添加学生信息
              
                              
             
                              
             
                              
             
                              
             
                              
                          返回         
     
 
 

<%@ page import="com.stu.po.Student" %> <%@ page import="java.util.List" %> <%@ page import="com.stu.po.Page" %> <%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>              
   
分页查询学生信息
     
                <%           Page page1 = (Page)request.getAttribute("page1");            for(Student student:page1.getStudent()){          %>                        <%             }           %>       
         
           
学号
           
姓名
           
性别
           
年龄
           
电话
          
               
<%=student.getSno() %>
               
<%=student.getSname() %>
               
<%=student.getSex() %>
               
<%=student.getAge() %>
               
<%=student.getPhone() %>
             
        <%         if(page1.getCurrentPage()==page1.getTotalPage()){       %>         
           首页           ">上一页           "/>         
       <%       } else if(page1.getCurrentPage()==0){       %>         
                      ">下一页           ">尾页         
       <%       } else{       %>         
           首页           ">上一页           "/>           ">下一页           ">尾页         
       <%         }       %>        返回     
 
    

<%@ page language="java" contentType="text/html; charset=utf-8"  pageEncoding="utf-8"%> <%@ page import="com.stu.po.Student" %> <%@ page import="java.util.List" %>    	  	   
 	
查看所有学生信息
 	
 		 			<%  				List allStudents = (List)session.getAttribute("allStudents"); 				for (int i = 0; i < allStudents.size(); i++) { 					Student s  = allStudents.get(i); 			%> 			 			<% 				} 			%> 		
 			
 				
学号
 				
姓名
 				
性别
 				
年龄
 				
电话
 				
操作
 			
 				
<%=s.getSno() %>
 				
<%=s.getSname() %>
 				
<%=s.getSex() %>
 				
<%=s.getAge() %>
 				
<%=s.getPhone() %>
 				
 					">删除 					">修改 				
 			
 		返回 	
  
   

<%@ page language="java" contentType="text/html; charset=utf-8"  pageEncoding="utf-8"%> <%@ page import="com.stu.po.Student" %>                                 
     
学生信息管理平台
      
         <%             Student s =(Student)request.getAttribute("student");         %>         
             
修改学生信息
             "/>             
                 "/>             
             
                 "/>             
             
                 "/>             
             
                 "/>             
                          返回         
     
 
 

2.JavaBean实体类封装数据

（1）学生信息类 (Student.java)

package com.stu.po;  public class Student {     //这是一个实体类，javabean      private int sno;     private String sname;     private String sex;     private int age;     private String phone;      public Student(int sno, String sname, String sex, int age, String phone) {         this.sno = sno;         this.sname = sname;         this.sex = sex;         this.age = age;         this.phone = phone;     }      public Student() {      }      public int getSno() {         return sno;     }      public void setSno(int sno) {         this.sno = sno;     }      public String getSname() {         return sname;     }      public void setSname(String sname) {         this.sname = sname;     }      public String getSex() {         return sex;     }      public void setSex(String sex) {         this.sex = sex;     }      public int getAge() {         return age;     }      public void setAge(int age) {         this.age = age;     }      public String getPhone() {         return phone;     }      public void setPhone(String phone) {         this.phone = phone;     } }  

（2）分页帮助类 (Page.java)

package com.stu.po;  import java.util.List;  //分页帮助类 public class Page {     private int currentPage;  //当前页面     private int pageSize;     //一页有多少条数据     private int totalCount;   //一共有多少条数据     private int totalPage;    //一共有多少页     private List student;     public Page() {      }     public Page(int currentPage, int pageSize, int totalCount, int totalPage, List student) {         this.currentPage = currentPage;         this.pageSize = pageSize;         this.totalCount = totalCount;         this.totalPage = totalPage;         this.student = student;     }      public int getCurrentPage() {         return currentPage;     }      public void setCurrentPage(int currentPage) {         this.currentPage = currentPage;     }      public int getPageSize() {         return pageSize;     }      public void setPageSize(int pageSize) {         this.pageSize = pageSize;     }      public int getTotalCount() {         return totalCount;     }      public void setTotalCount(int totalCount) {         this.totalCount = totalCount;     }      public int getTotalPage() {         return totalPage;     }      public void setTotalPage(int totalPage) {         this.totalPage = totalPage;     }      public List getStudent() {         return student;     }      public void setStudent(List student) {         this.student = student;     } }  

（3）JDBC工具类 (DBTools.java)

package com.stu.utils;  public interface DBTools {     public static final String DRIVER_CLASS = "com.mysql.jdbc.Driver";     public static final String CONN_STR = "jdbc:mysql://localhost:3306/studentmanager?userSSL=false&serverTimezone=Asia/Shanghai";     public static final String USRENAME = "root";     public static final String PWD = "123456";  }  

3.三层架构

（1）表示层servlet

① 用户登录表示层 (LoginServlet.java)

package com.stu.servlet; import java.io.IOException;  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 javax.servlet.http.HttpSession;  import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  @WebServlet("/LoginServlet") public class LoginServlet extends HttpServlet{      @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         this.doPost(req, resp);     }      @Override     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {          StudentService service = new StudentServiceImpl();         HttpSession session = request.getSession();          if (session.getAttribute("loginErrorMessage") != null) {             session.invalidate();         }         String uid = request.getParameter("uid");         String pwd = request.getParameter("pwd");           int _uid = Integer.parseInt(uid);         boolean result = service.login(_uid, pwd);          if(result){             session.setAttribute("login", "log");             response.sendRedirect("main.jsp");         }else{             response.sendRedirect("index.jsp");         }      }  }  

② 用户注册表示层 (RegisterServlet.java)

package com.stu.servlet;  import java.io.IOException;  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 javax.servlet.http.HttpSession;  import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  @WebServlet("/RegisterServlet") public class RegisterServlet extends HttpServlet{      @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         this.doPost(req, resp);     }      @Override     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {          StudentService service = new StudentServiceImpl();         String uid = request.getParameter("uid");         String pwd = request.getParameter("pwd");         int _uid = Integer.parseInt(uid);         boolean result = service.addLogin(_uid,pwd);          if(!result) {             request.setAttribute("register", "reg");             request.getRequestDispatcher("index.jsp").forward(request, response);         }else {             request.getRequestDispatcher("register.jsp").forward(request, response);         }      }  }  

③ 分页查询表示层 (ShowStudentsByPageServlet.java)

package com.stu.servlet;  import java.io.IOException; import java.util.List;  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 javax.servlet.http.HttpSession;  import com.stu.po.Page; import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  @WebServlet("/ShowStudentsByPageServlet") public class ShowStudentsByPageServlet extends HttpServlet{      @Override     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {         StudentService Service = new StudentServiceImpl();         int count = Service.getTotalCount();          Page page = new Page();           String currentPage = request.getParameter("currentPage");          if(currentPage == null) {             currentPage = "0";         }         int _currentPage = Integer.parseInt(currentPage);         page.setCurrentPage(_currentPage);          int totalCount = Service.getTotalCount();         page.setTotalCount(totalCount);           int pageSize = 5;         int totalPage = (totalCount / pageSize) + 1;         page.setTotalPage(totalPage+1);           page.setPageSize(pageSize);          List student = Service.queryStudentsByPageNo(_currentPage, pageSize);         page.setStudent(student);          request.setAttribute("page1", page);         request.getRequestDispatcher("showAllStudentsByPageNo.jsp").forward(request, response);     }  }  

④ 查询所学生信息表示层 (ShowAllStudentsServlet.java)

package com.stu.servlet;  import java.io.IOException; import java.util.List;  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 javax.servlet.http.HttpSession;  import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  @WebServlet("/ShowAllStudentsServlet") public class ShowAllStudentsServlet extends HttpServlet{      @Override     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {         StudentService service = new StudentServiceImpl();         HttpSession  session =   request.getSession();         List allStudents = service.getAllStudents();         session.setAttribute("allStudents", allStudents);         response.sendRedirect("showAllStudents.jsp");     }  }  

⑤ 添加学生表示层 (AddServlet.java)

package com.stu.servlet;  import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  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 javax.servlet.http.HttpSession; import java.io.IOException;  @WebServlet("/AddServlet") public class AddServlet extends HttpServlet{      @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         this.doPost(req, resp);     }      @Override     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {          StudentService service = new StudentServiceImpl();         String sno  = request.getParameter("sno");         String sname  = request.getParameter("sname");         String sex  = request.getParameter("sex");         String age  = request.getParameter("age");         String phone  = request.getParameter("phone");          int _sno = 0;         if(sno != null || "".equals(sno)){             _sno = Integer.parseInt(sno);         }          int _age = 0;         if (age !=null || "".equals(age)){             _age = Integer.parseInt(age);         }          Student s = new Student(_sno, sname, sex, _age, phone);         int result = service.addStudent(s);          HttpSession session = request.getSession();         session.setAttribute("student", "stu");         response.sendRedirect("main.jsp");      } }  

⑥ 删除学生表示层 (DeleteServlet.java)

package com.stu.servlet;  import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  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;   @WebServlet("/DeleteServlet") public class DeleteServlet extends HttpServlet {      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {         //1.获取sno         String sno = request.getParameter("sno");          int _sno = 0;         if(sno != null && !"".equals(sno)){             _sno = Integer.parseInt(sno);         }          //2.执行删除         StudentService service = new StudentServiceImpl();         Student stu = service.deleteStudent(_sno);         //3.跳转到列表页         request.setAttribute("stu", stu);         request.getRequestDispatcher("ShowAllStudentsServlet").forward(request,response);     } }  

⑦ 根据学号查询学生信息表示层 (QueryStudentBySnoSevlet.java)

package com.stu.servlet;  import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  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;    @WebServlet("/QueryStudentBySnoServlet") public class QueryStudentBySnoServlet extends HttpServlet {      @Override     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {         //获取sno;         String sno = request.getParameter("sno");         int _sno = 0;         if(sno != null && !"".equals(sno)){             _sno = Integer.parseInt(sno);         }          //2.查询学生数据         StudentService service = new StudentServiceImpl();         Student student = service.queryStudentBySno(_sno);          //3.显示数据         //存数据         request.setAttribute("student", student);         //跳转         request.getRequestDispatcher("updateStudent.jsp").forward(request,response);      } }  

⑧ 修改学生信息表示层 (UpdateServlet.java)

package com.stu.servlet;  import com.stu.po.Student; import com.stu.service.StudentService; import com.stu.service.StudentServiceImpl;  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 javax.servlet.http.HttpSession; import java.io.IOException; import java.util.List;  @WebServlet("/UpdateServlet") public class UpdateServlet extends HttpServlet {      protected void doGet(HttpServletRequest request, HttpServletResponse resp) throws ServletException, IOException {          String sno = request .getParameter("sno");         String sname  = request.getParameter("sname");         String sex  = request.getParameter("sex");         String age  = request.getParameter("age");         String phone  = request.getParameter("phone");          int _sno = 0;         if(sno != null && !"".equals(sno)){             _sno = Integer.parseInt(sno);         }         int _age = 0;         if(age != null && !"".equals(age)){             _age = Integer.parseInt(age);         }           Student stu = new Student(_sno, sname, sex, _age, phone);          StudentService service = new StudentServiceImpl();         service.updateStudentBySno(_sno,stu);          //3.跳转界面         request.getRequestDispatcher("ShowAllStudentsServlet").forward(request, resp);      } }  

⑨ 退出登录表示层 (QuitServlet.java)

package com.stu.servlet;  import java.io.IOException;  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 javax.servlet.http.HttpSession;   @WebServlet("/QuitServlet") public class QuitServlet extends HttpServlet{      @Override     protected void doGet(HttpServletRequest request, HttpServletResponse resp) throws ServletException, IOException {         HttpSession  session =   request.getSession();         session.invalidate();//清空session对象中的所有属性数据内容         resp.sendRedirect("index.jsp");     } }   

（2）业务逻辑层service

① Service接口（StudentService.java）

package com.stu.service;  import java.util.List;  import com.stu.po.Student;  public interface StudentService {      //service表示业务逻辑层,定义的每一个方法实际上对应的就是用户的一个需求(请求)      public boolean login(int uid,String pwd);      public boolean addLogin(int uid, String pwd);      public List getAllStudents();      public List queryStudentsByPageNo(int current, int pageSize);      public Student deleteStudent(int sno);      public Student queryStudentBySno(int sno);      public int updateStudentBySno(int sno, Student stu) ;      public int getTotalCount();      public int addStudent(Student student);      }  

② 接口的实现类（StudentServiceImpl.java）

package com.stu.service;  import java.util.List; import com.stu.dao.StudentDao; import com.stu.dao.StudentDaoImpl; import com.stu.po.Student;  public class StudentServiceImpl implements StudentService {      StudentDao dao = new StudentDaoImpl();      //登陆     @Override     public boolean login(int uid, String pwd) {         return dao.login(uid, pwd);     }      // 注册     @Override     public boolean addLogin(int uid, String pwd){         return dao.addLogin(uid, pwd);     }      // 查询所有学生     @Override     public List getAllStudents() {         return dao.getAllStudents();     }      // 分页查询     @Override     public List queryStudentsByPageNo(int current, int pageSize) {         return dao.queryStudentByPage(current,pageSize);     }      // 删除学生     @Override     public Student deleteStudent(int sno){         return dao.deleteStudent(sno);     }      // 修改学生信息，要先根据学号查询学生信息     public Student queryStudentBySno(int sno) {         return dao.queryStudentBySno(sno);      }      //更改学生信息     public int updateStudentBySno(int sno, Student stu) {         return dao.updateStudentBySno(sno,stu);     }          //查询总条数     @Override     public int getTotalCount() {         return dao.getTotalCount();     }      @Override     public int addStudent(Student student) {         return dao.addStudent(student);     }      }  

（3）数据访问层dao

① 接口（StudentDao.java）

package com.stu.dao;  import java.util.List;  import com.stu.po.Student;  public interface StudentDao {      public boolean login(int uid ,String pwd);      public boolean addLogin(int uid, String pwd);      public List getAllStudents();      public List queryStudentByPage(int currentPage,int pageSize);      public Student deleteStudent(int sno);      public Student queryStudentBySno(int sno);      public int updateStudentBySno(int sno,Student stu);      //查询总数据数     public int getTotalCount();      public int addStudent(Student student);     }  

② 接口的实现类（StudentDaoImpl.java）

package com.stu.dao;  import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.List;  import com.stu.po.Student; import com.stu.utils.DBTools;  public class StudentDaoImpl implements StudentDao {      Connection conn = null; // 连接对象     Statement st = null; // 语句对象     ResultSet rs = null; // 结果集合对象      @Override     public boolean login(int uid, String pwd) {         // 在这里需要连接数据库，根据int sno, String pwd这两个参数来查询student表         // jdbc         // 1:配置环境，下载数据库连接驱动jar文件，拷贝到项目中来         // 2:加载驱动，根据驱动创建数据库的连接对象          try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动              conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             // 3:执行sql语句，完成对数据库中表的数据的增删该查。必须创建一个语句对象（执行sql语句的）             st = conn.createStatement();              int count = 0;             String sqlStr = "select * from login where uid =" + uid + " and pwd = '" + pwd + "'";              rs = st.executeQuery(sqlStr);             while(rs.next()) {                 count++;             }             if(count>0)                 return true;             else                 return false;          } catch (ClassNotFoundException e) {             e.printStackTrace();         } catch (SQLException e) {             e.printStackTrace();         }         return false;     }       @Override     public List getAllStudents() {         try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动              conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             // 3:执行sql语句，完成对数据库中表的数据的增删该查。必须创建一个语句对象（执行sql语句的）             st = conn.createStatement();              String sqlStr = "select * from student";              rs = st.executeQuery(sqlStr);              List allStudents = new ArrayList();              while (rs.next()) {                 int _sno = rs.getInt(1);                 String _sname = rs.getString(2);                 String _sex = rs.getString(3);                 int _age = rs.getInt(4);                 String _phone = rs.getString(5);                 Student s = new Student(_sno, _sname, _sex, _age, _phone);                 allStudents.add(s);             }              return allStudents;          } catch (ClassNotFoundException e) {             e.printStackTrace();         } catch (SQLException e) {             e.printStackTrace();         }          return null;     }       public List queryStudentByPage(int current, int pageSize) {         try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动              conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             // 3:执行sql语句，完成对数据库中表的数据的增删该查。必须创建一个语句对象（执行sql语句的）             st = conn.createStatement();              int startPosition = current * pageSize;              String sqlStr = "select * from student limit " + startPosition + "," + pageSize;             rs = st.executeQuery(sqlStr);             List allStudents = new ArrayList();             while (rs.next()) {                 int _sno = rs.getInt(1);                 String _sname = rs.getString(2);                 String _sex = rs.getString(3);                 int _age = rs.getInt(4);                 String _phone = rs.getString(5);                 Student s = new Student(_sno, _sname, _sex, _age, _phone);                 allStudents.add(s);             }             return allStudents;         } catch (ClassNotFoundException e) {             e.printStackTrace();         } catch (SQLException e) {             e.printStackTrace();         }          return null;     }      public int getTotalCount() {//查询总数据数          try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动              conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             // 3:执行sql语句，完成对数据库中表的数据的增删该查。必须创建一个语句对象（执行sql语句的）             st = conn.createStatement();             String sql = "select count(*) from student";             rs = st.executeQuery(sql);             while (rs.next()){                 int totalCount = rs.getInt(1);             }           }catch (Exception e){             e.printStackTrace();         }         return 0;     }      @Override     public int addStudent(Student student) {          try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动              conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             st = conn.createStatement();             String sqlStr = "insert into student values("+student.getSno()+",'" + student.getSname()+ "','" + student.getSex() +"',"+student.getAge()+",'"+student.getPhone()+"')";             System.out.println(sqlStr);             int result = st.executeUpdate(sqlStr);          } catch (ClassNotFoundException e) {             e.printStackTrace();         } catch (SQLException e) {             e.printStackTrace();         }         return 0;     }       @Override     public boolean addLogin(int uid, String pwd) {         try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动              conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             st = conn.createStatement();             String sqlStr = "insert into login values(" + uid + ",'" + pwd + "')";              int result = st.executeUpdate(sqlStr);          } catch (ClassNotFoundException e) {             e.printStackTrace();         } catch (SQLException e) {             e.printStackTrace();         }         return false;     }       @Override     public Student deleteStudent(int sno) {         try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动             conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             st = conn.createStatement();             String sqlStr = "delete from student where sno = " + sno;             System.out.println(sqlStr);             int result = st.executeUpdate(sqlStr);          } catch (Exception e){             e.printStackTrace();         }         return null;     }      @Override     public Student queryStudentBySno(int sno) {         try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动              conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);              st = conn.createStatement();              String sqlStr = "select * from student where sno = "+ sno;             rs = st.executeQuery(sqlStr);              if (rs.next()) {                 int _sno = rs.getInt(1);                 String _sname = rs.getString(2);                 String _sex = rs.getString(3);                 int _age = rs.getInt(4);                 String _phone = rs.getString(5);                 Student s = new Student(_sno, _sname, _sex, _age, _phone);                 return s;             }          } catch (Exception e) {             e.printStackTrace();         }         return null;     }       @Override     public int updateStudentBySno(int sno, Student stu){         try {             Class.forName(DBTools.DRIVER_CLASS);// 加载驱动             conn = DriverManager.getConnection(DBTools.CONN_STR, DBTools.USRENAME, DBTools.PWD);             st = conn.createStatement();             String sql = "update student set sname= '"+stu.getSname()+"', sex='"+stu.getSex()+"', age="+stu.getAge()+", phone='"+stu.getPhone()+"' where sno="+sno;             System.out.println(sql);             int result = st.executeUpdate(sql);          } catch (Exception e){             e.printStackTrace();         }         return 0;     } }