使用jsp-servlet-service-dao四层结构完成用户信息的增删改查操作（2020.12.22）

需求：
使用Servlet和四层结构知识，改进只用JSP（不分层）完成用户信息的增删改查操作的信息管理系统，使其具有更好的软件结构，以及提升可读性和可扩展性。（jsp-servlet-service-dao）

目录结构

登录

（1）LoginServlet的doPost方法

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   System.out.println("login-post");
   //设置编码
   request.setCharacterEncoding("utf-8");
   Map<String, String[]> map = request.getParameterMap();
   //封装User对象
   User user = new User();
   try {
      BeanUtils.populate(user,map);
   } catch (IllegalAccessException e) {
      e.printStackTrace();
   } catch (InvocationTargetException e) {
      e.printStackTrace();
   }
   //调用Service查询
   userService userservice = new userServiceImpl();
   User loginUser=userservice.login(user);
   //判断是否登录成功
   HttpSession session = request.getSession();
   if(loginUser != null){
      session.setAttribute("user",loginUser);//登录成功 将用户存入session
      response.sendRedirect(request.getContextPath()+"/index.jsp");//跳转到首页
   }else{
      request.setAttribute("login_msg","用户名或密码错误！");//登录失败
      request.getRequestDispatcher("/login.jsp").forward(request,response);//跳转登录页面
   }
}

（2）Dao层用户登录校验

@Override
public User login(User u) {
   if (u.getUsername()==null||u.getUsername().equals("")||u.getPassword()==null||u.getPassword().equals("")){
      return null;
   }
   User user=new User();
   try {
      conn = JDBCUtils.getConnection();
      String sql="select * from user_list where user_name=? and user_password = ?";
      System.out.println("sql："+sql);
      pst = conn.prepareStatement(sql);
      pst.setString(1,u.getUsername());
      pst.setString(2,u.getPassword());
      rs=pst.executeQuery();    //注意：执行的适合不需要传入sql语句
      if(rs.next()){    //存在一行数据,即账号密码正确
         user.setAge(rs.getInt("user_age"));
         user.setUsername(rs.getString("user_id"));
         user.setPassword(u.getPassword());
         user.setUserRole(rs.getString("user_role"));
         user.setUserId(u.getUsername());
         return user;
      }
   } catch (SQLException e) {
      e.printStackTrace();
   } finally {
      JDBCUtils.close(rs, pst, conn);    //释放连接
   }
   return null;
}

注册

（1）registServlet的doPost方法

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
   System.out.println("regist-post");
   //设置编码
   request.setCharacterEncoding("utf-8");
   Map<String, String[]> map = request.getParameterMap();
   //封装User对象
   User user = new User();
   try {
      BeanUtils.populate(user,map);
   } catch (IllegalAccessException e) {
      e.printStackTrace();
   } catch (InvocationTargetException e) {
      e.printStackTrace();
   }
   //单选框的值BeanUtils无法自己封装
   String userRole = request.getParameter("userRole");
   user.setUserRole(userRole);
   System.out.println(user);
   //调用Service查询
   userService userservice = new userServiceImpl();
   int result = userservice.insert(user);
   HttpSession session = request.getSession();
   if (result == 1){     //添加成功
      session.setAttribute("user",user);//注册成功 将用户存入session
      session.setAttribute("role",user.getUserRole());
      response.sendRedirect(request.getContextPath()+"/index.jsp");//跳转到首页
   }else{
      request.setAttribute("regist_msg","注册失败！");//登录失败
      request.getRequestDispatcher("/regist.jsp").forward(request,response);//跳转登录页面
   }
}

（2）注册功能的dao层代码

@Override
public int insert(User user) {
   if (user==null){
      return 0;
   }
   int result=-1;
   try {
      conn = JDBCUtils.getConnection();
      String sql="insert into user_list(user_id,user_age,user_name,user_password,user_role) values(?,?,?,?,?)";
      System.out.println("sql："+sql);
      pst = conn.prepareStatement(sql);
      //动态添加数据
      pst.setString(1,user.getUserId());
      pst.setInt(2,user.getAge());
      pst.setString(3,user.getUsername());
      pst.setString(4,user.getPassword());
      pst.setString(5,user.getUserRole());
      result=pst.executeUpdate();    //注意：执行的适合不需要传入sql语句
   } catch (SQLException e) {
      e.printStackTrace();
   } finally {
      JDBCUtils.close(rs, pst, conn);    //释放连接
   }
   return result;
}

（3）进行删除时验证用户身份js方法

function del(user_id,user_role,userName){
    if (user_role.toString()=="用户"){
        alert("您没有权限删除其他人");
        return false;
    }
    if(confirm("确认删除"+userName+"吗?")){
        window.location.href= "delete.jsp?user_id="+user_id+"&user_name="+userName;
    }else{
        window.location.href="index.jsp";
    }
}

（4）删除用户的deleteServlet的doGet方法

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   System.out.println("delete-get");
   //设置编码
   request.setCharacterEncoding("utf-8");
   //获取删除的user_id
   String user_id = request.getParameter("user_id");
   userService service = new userServiceImpl();
   service.delete(user_id);
   //跳转到查询所有Servlet
   response.sendRedirect(request.getContextPath()+"/index.jsp");

（5）更新用户信息updateServlet的doPost方法

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
   System.out.println("update-post");
   //设置编码
   request.setCharacterEncoding("utf-8");
   Map<String, String[]> map = request.getParameterMap();
   //封装User对象
   User user = new User();
   try {
      BeanUtils.populate(user,map);
   } catch (IllegalAccessException e) {
      e.printStackTrace();
   } catch (InvocationTargetException e) {
      e.printStackTrace();
   }
   HttpSession session = request.getSession();
   //调用Service查询
   userService userservice = new userServiceImpl();
   int result=userservice.update(user);
   if (result == 1){     //添加成功
      response.sendRedirect(request.getContextPath()+"/index.jsp");//跳转到首页
   }else{
      //修改失败
   }
}

总结

分层编写代码。使用Dao进行与数据库的增删改查操作；Service层进行业务操作；Servlet进行处理请求。在jsp表单提交的时候调用Servlet处理请求。采用分层管理代码，将方法的定义和实现抽离。使用工具类读取配置文件的时候，要保证路径正确，不然会读取不到报错。在表单中使用post请求，则应该编写servlet中的doPost方法。采用分层方法管理代码，代码的管理起来更加方便了，可读性更高，修改更加简便

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