Java | 超市管理系统demo

1.系统功能简介
2. 项目搭建
- 2.1 搭建一个maven web项目
- 2.2 配置Tomcat
- 2.3 测试Tomcat
- 2.4 导入依赖
- 2.5 创建项目结构
- 2.6 编写实体类（ORM映射）
- 2.7 编写基础公共类（BaseDao）
- 2.8 编写字符编码过滤器
3. 登录功能
- 3.1 登录功能简介
- 3.2 前端页面以及设置首页
- 3.3 Dao接口
- 3.4 Dao实现类
- 3.5 Service接口
- 3.6 Service实现类
- 3.7 Servlet
- 3.8 注销功能
- 3.9 过滤器，使在注销情况下不能访问后台页面
4. 密码修改功能
- 4.1 导入前端素材
- 4.2 功能实现思路
- 4.3 Dao层
- 4.4 Service层
- 4.5 Servlet层
5. 用户管理功能
- 5.1 功能实现思路
- 5.2 准备素材
- 5.3 查询用户数量
- @Test 测试方法
- 5.4 获取用户列表
- 5.5 获取角色列表
- 一个小tip
- 5.6 显示用户的Servlet
6.我的总结
- 6.1 重点
- 6.2 难点
- 6.3 不足之处

1.系统功能简介

2. 项目搭建

2.1 搭建一个maven web项目

2.2 配置Tomcat

2.3 测试Tomcat

2.4 导入依赖

<dependencies><dependency><groupId>javax.servlet</groupId><artifactId>servlet-api</artifactId><version>2.5</version></dependency><dependency><groupId>javax.servlet.jsp</groupId><artifactId>javax.servlet.jsp-api</artifactId><version>2.3.3</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency><dependency><groupId>javax.servlet.jsp.jstl</groupId><artifactId>jstl-api</artifactId><version>1.2</version></dependency><dependency><groupId>taglibs</groupId><artifactId>standard</artifactId><version>1.1.2</version></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version></dependency><!-- https://mvnrepository.com/artifact/com.alibaba/fastjson --><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.61</version></dependency><!-- https://mvnrepository.com/artifact/com.alibaba/fastjson --><dependency><groupId>com.alibaba</groupId><artifactId>fastjson</artifactId><version>1.2.61</version></dependency>

2.5 创建项目结构

2.6 编写实体类（ORM映射）

2.7 编写基础公共类（BaseDao）

getConnection方法：获取数据库的链接
execute方法：编写公共查询方法
execute方法：编写增删改公共方法（方法重载）
closeResource方法：释放资源

package com.young.dao;import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;//操作数据库的公共类
public class BaseDao {private static String driver;private static String url;private static String username;private static String password;//静态代码块，类加载的时候就初始化了static {//读取操作数据库的资料Properties properties = new Properties();InputStream stream = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");try {properties.load(stream);} catch (IOException e) {e.printStackTrace();}driver = properties.getProperty("driver");url = properties.getProperty("url");username = properties.getProperty("username");password = properties.getProperty("password");}//getConnection方法：获取数据库的链接//返回值：一个数据库的连接对象connectionpublic static Connection getConnection() throws SQLException {Connection connection=null;try {Class.forName(driver);connection = DriverManager.getConnection(url, username, password);} catch (ClassNotFoundException e) {e.printStackTrace();}return  connection;}//execute方法：编写公共查询方法//返回值：查询结果ResultSetpublic static ResultSet execute(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet,String sql,Object[] params) throws SQLException {preparedStatement = connection.prepareStatement(sql);for (int i = 0; i < params.length; i++) {//注意这里的下标preparedStatement.setObject(i+1,params[i]);}resultSet = preparedStatement.executeQuery();return resultSet;}//execute方法：编写增删改公共方法（方法重载）//返回值：数据库中改变的行数 （int）updatepublic static int execute(Connection connection,String sql,Object[] params,PreparedStatement preparedStatement) throws SQLException {preparedStatement = connection.prepareStatement(sql);for (int i = 0; i < params.length; i++) {preparedStatement.setObject(i+1,params[i]);}int update = preparedStatement.executeUpdate();return update;}//closeResource方法：释放资源//返回值：是否成功 flagpublic static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){boolean flag=true;if(connection!=null){try {connection.close();} catch (SQLException e) {e.printStackTrace();flag=false;}}if(preparedStatement!=null){try {preparedStatement.close();} catch (SQLException e) {e.printStackTrace();flag=false;}}if(resultSet!=null){try {resultSet.close();} catch (SQLException e) {e.printStackTrace();flag=false;}}return flag;}}

数据库配置文件:

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/smbms?useSSL=true&useUnicode=true&characterEncoding=utf-8
username=root
password=123456

2.8 编写字符编码过滤器

public class CharacterEncodingFilter  implements Filter {public void init(FilterConfig filterConfig) throws ServletException {}public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {servletRequest.setCharacterEncoding("utf-8");servletResponse.setCharacterEncoding("utf-8");filterChain.doFilter(servletRequest,servletResponse);}public void destroy() {}
}

映射：

    <!--字符编码过滤器--><filter><filter-name>CharacterEncodingFilter</filter-name><filter-class>com.young.filter.CharacterEncodingFilter</filter-class></filter><filter-mapping><filter-name>CharacterEncodingFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping>

3. 登录功能

3.1 登录功能简介

3.2 前端页面以及设置首页

导入前端页面，设置欢迎页

    <!--设置欢迎页面--><welcome-file-list><welcome-file>login.jsp</welcome-file></welcome-file-list>

3.3 Dao接口

//得到要登录的用户public User getLoginUser (Connection connection, String userCode)throws SQLException;

3.4 Dao实现类

//得到要登录的用户public User getLoginUser(Connection connection, String userCode) throws SQLException {PreparedStatement preparedStatement=null;ResultSet rs = null;User user = null;if(connection!=null){String sql="select * from smbms_user where userCode=?";//这里可以进行改进，我觉得应该是用户名和密码都正确，才可以在数据库中查询到该用户。Object[] paras={userCode};rs = BaseDao.execute(connection, preparedStatement, rs, sql, paras);if(rs.next()){user = new User();user.setId(rs.getInt("id"));user.setUserCode(rs.getString("userCode"));user.setUserName(rs.getString("userName"));user.setUserPassword(rs.getString("userPassword"));user.setGender(rs.getInt("gender"));user.setBirthday(rs.getDate("birthday"));user.setPhone(rs.getString("phone"));user.setAddress(rs.getString("address"));user.setUserRole(rs.getInt("userRole"));user.setCreatedBy(rs.getInt("createdBy"));user.setCreationDate(rs.getTimestamp("creationDate"));user.setModifyBy(rs.getInt("modifyBy"));user.setModifyDate(rs.getTimestamp("modifyDate"));}}return user;}

3.5 Service接口

//用户登录public User login(String usercode,String password);

3.6 Service实现类

 //业务层都会调用dao层，所以我们要引入Dao层；private UserDao userDao;public UserServiceImp(){userDao= new UserDaoImp();}//用户登录public User login(String usercode, String password) {Connection connection=null;User user=null;try {connection = BaseDao.getConnection();//通过业务层调用对应的具体的数据库操作user = userDao.getLoginUser(connection, usercode);} catch (SQLException e) {e.printStackTrace();}finally {BaseDao.closeResource(connection,null,null);}return user;}

3.7 Servlet

public class LoginServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("LoginServlet--start");//获取用户名和密码String userCode = req.getParameter("userCode");String userPassword = req.getParameter("userPassword");//和数据库中的密码进行对比，调用业务层；UserService userService = new UserServiceImp();User user = userService.login(userCode, userPassword); //这里已经把登录的人给查出来了if(user!=null && user.getUserPassword().equals(userPassword)){//查有此人，可以登录//将用户的信息放到Session中req.getSession().setAttribute(Constant.USER_SESSION,user);//跳转到主页resp.sendRedirect("jsp/frame.jsp");}else {//查无此人，无法登录//转发回登录页面，顺带提示它，用户名或者密码错误；req.setAttribute("error","用户名或者密码不正确");req.getRequestDispatcher("login.jsp").forward(req,resp);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

3.8 注销功能

public class LogoutServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.getSession().removeAttribute(Constant.USER_SESSION);resp.sendRedirect(req.getContextPath()+"/login.jsp");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}
}

3.9 过滤器，使在注销情况下不能访问后台页面

public class SysFilter implements Filter {public void init(FilterConfig filterConfig) throws ServletException {}public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {HttpServletRequest req = (HttpServletRequest) servletRequest;HttpServletResponse resp = (HttpServletResponse) servletResponse;Object user = req.getSession().getAttribute(Constant.USER_SESSION);if(user==null){resp.sendRedirect(req.getContextPath()+"/error.jsp");}else{filterChain.doFilter(servletRequest,servletResponse);}}public void destroy() {}
}

4. 密码修改功能

4.1 导入前端素材

导入 pwdmodify.jsp文件：

4.2 功能实现思路

从底层向上层进行代码实现

4.3 Dao层

UserDao 接口：

//修改当前用户的密码public boolean updatePwd(Connection connection,int id,String password) throws SQLException;

UserDao 接口实现类：

//修改当前用户的密码public boolean updatePwd(Connection connection, int id, String password) throws SQLException {boolean flag=false;PreparedStatement preparedStatement=null;String sql="update smbms_user set userPassword =? where id=?";if(connection!=null){Object[] params={id,password};int execute = BaseDao.execute(connection, sql, params, preparedStatement);flag=true;BaseDao.closeResource(null,preparedStatement,null);}return flag;}

4.4 Service层

UserService接口：

    //修改密码public boolean updatePassword(int id, String password);

UserService实现类：

    //密码更新public boolean updatePassword(int id, String password) {Connection connection=null;boolean flag=false;try {connection = BaseDao.getConnection();flag = userDao.updatePwd(connection, id, password);} catch (SQLException e) {e.printStackTrace();} finally {BaseDao.closeResource(connection,null,null);}return flag;}

4.5 Servlet层

Servlet层可以通过提出取方法实现复用
下面的代码中，通过updatePassword()方法和pwdModify()方法，实现doGet的复用

package com.young.servlet.user;import com.alibaba.fastjson.JSONArray;
import com.mysql.jdbc.StringUtils;
import com.young.pojo.User;
import com.young.service.user.UserService;
import com.young.service.user.UserServiceImp;
import com.young.util.Constant;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;public class UpdataPassword extends HttpServlet {@Override//实现Servlet的复用protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String method = req.getParameter("method");if(method.equals("savepwd")){//与jsp/pwdmodify.jsp 中 <input type="hidden" name="method" value="savepwd"> 代码对应this.updatePassword(req,resp);}else if(method.equals("pwdmodify")){//与js/pwdmodify.js中 data:{method:"pwdmodify",oldpassword:oldpassword.val()} 代码对应this.pwdModify(req,resp);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}//密码更新private void updatePassword(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//从Session中获取IDObject o = req.getSession().getAttribute(Constant.USER_SESSION);String newpassword = req.getParameter("newpassword");boolean flag=false;if(o!=null && newpassword!=null){UserService userService = new UserServiceImp();flag = userService.updatePassword((int) (((User) o).getId()), newpassword);if(flag){//密码修改成功：提示密码修改成功，移除Sessionreq.setAttribute("message","密码修改成功，请重新登录");req.getSession().removeAttribute(Constant.USER_SESSION);}else {//密码修改失败：提示密码修改修改req.setAttribute("message","密码修改失败");}}else {req.setAttribute("message","新密码设置不符合要求");}req.getRequestDispatcher("pwdmodify.jsp").forward(req,resp);//转发与重定向// resp.sendRedirect(req.getContextPath()+"/login.jsp");}//验证旧密码（旧密码从Session中获取即可）private void pwdModify(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException{Object o = req.getSession().getAttribute(Constant.USER_SESSION);String oldpassword = req.getParameter("oldpassword");//万能的Map : 结果集HashMap<String, String> hashMap = new HashMap<String, String>();if(o==null){//Session失效了，session过期了hashMap.put("result", "sessionerror");}else if(StringUtils.isNullOrEmpty(oldpassword)){//输入的密码为空hashMap.put("result", "error");}else {String userPassword = ((User) o).getUserPassword();if(oldpassword.equals(userPassword)){hashMap.put("result","true");}else {hashMap.put("result","false");}}resp.setContentType("application/json");PrintWriter writer = resp.getWriter();//JSONArray 阿里巴巴的JSON工具类 , 用于转换格式/*hashMap = ["result","sessionerror","result","error"]Json格式 = {key：value}*/writer.write(JSONArray.toJSONString(hashMap));writer.flush();writer.close();}}

5. 用户管理功能

5.1 功能实现思路

5.2 准备素材

导入分页的工具类

package com.young.util;public class PageSupport {//当前页码-来自于用户输入private int currentPageNo = 1;//总数量（表）private int totalCount = 0;//页面容量private int pageSize = 0;//总页数-totalCount/pageSize（+1）private int totalPageCount = 1;public int getCurrentPageNo() {return currentPageNo;}public void setCurrentPageNo(int currentPageNo) {if(currentPageNo > 0){this.currentPageNo = currentPageNo;}}public int getTotalCount() {return totalCount;}public void setTotalCount(int totalCount) {if(totalCount > 0){this.totalCount = totalCount;//设置总页数this.setTotalPageCountByRs();}}public int getPageSize() {return pageSize;}public void setPageSize(int pageSize) {if(pageSize > 0){this.pageSize = pageSize;}}public int getTotalPageCount() {return totalPageCount;}public void setTotalPageCount(int totalPageCount) {this.totalPageCount = totalPageCount;}public void setTotalPageCountByRs(){if(this.totalCount % this.pageSize == 0){this.totalPageCount = this.totalCount / this.pageSize;}else if(this.totalCount % this.pageSize > 0){this.totalPageCount = this.totalCount / this.pageSize + 1;}else{this.totalPageCount = 0;}}
}

上述代码中复习的知识点：
面向对象三大特性：封装继承多态
其中，封装指的是：属性私有，set/get方法，在set中限定一些不安全的情况

2. 用户列表页面（jsp/userlist.jsp）导入

5.3 查询用户数量

UserDao

 //查询用户数量public int getUserNum(Connection connection,String username,int userRole)throws SQLException;

UserDaoImpl

 //查询用户数量public int getUserNum(Connection connection, String username, int userRole) throws SQLException {PreparedStatement preparedStatement =null;ResultSet resultSet=null;int count=0;if(connection!=null){StringBuffer sql = new StringBuffer();sql.append(" select count(1) as count from smbms.smbms_user u,smbms.smbms_role r where u.userRole=r.id");ArrayList<Object> list = new ArrayList<Object>();if(!StringUtils.isNullOrEmpty(username)){sql.append(" and u.username like ?");list.add("%"+username+"%");}if(userRole>0){sql.append(" and u.userRole = ?");list.add(userRole);}//把list转换为数组Object[] params = list.toArray();System.out.println("UserDaoImp -> getUserNum"+sql);ResultSet rs = BaseDao.execute(connection, preparedStatement, resultSet, sql.toString(), params);if(rs.next()){count=rs.getInt("count");}}BaseDao.closeResource(null,preparedStatement,resultSet);return count;}

UserService

//查询记录数public int getUserCount(String username,int userRole);

UserServiceImpl

//查询public int getUserCount(String username, int userRole) {Connection connection=null;int num = 0;try {connection = BaseDao.getConnection();num = userDao.getUserNum(connection, username, userRole);} catch (SQLException e) {e.printStackTrace();}finally {BaseDao.closeResource(connection,null,null);}return num;}

@Test 测试方法

在导入junit依赖的情况下，使用@Test，可以不用main方法调用就可以测试出运行结果，是一种测试方法。
注意被测试的方法必须是public修饰的！

在UserServiceImpl里面继续局部测试

 @Testpublic void test(){UserServiceImp imp = new UserServiceImp();int count = imp.getUserCount(null, 0);System.out.println(count);}

输出：

依赖：

    <dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version></dependency>

5.4 获取用户列表

UserDao

//通过查询获取用户列表 userlistpublic List<User> getUserList(Connection connection,String userName,int userRole,int currentPageNo,int pageSize)throws SQLException;

UserDaoImp

//通过查询获取用户列表userlistpublic List<User> getUserList(Connection connection, String userName, int userRole, int currentPageNo, int pageSize) throws SQLException {PreparedStatement preparedStatement=null;ResultSet resultSet=null;List<User> userlist = new ArrayList<User>();if(connection!=null){ArrayList<Object> list = new ArrayList<Object>();StringBuffer sql=new StringBuffer();//sql写数据库命令//list记录数据库中的参数sql.append("select u.*,r.roleName as userRoleName from smbms.smbms_user u,smbms.smbms_role r where u.userRole=r.id");if(!StringUtils.isNullOrEmpty(userName)){sql.append(" and u.username like ?");list.add("%"+userName+"%");}if(userRole>0){sql.append(" and u.userRole = ?");list.add(userRole);}//分页的sql写法：limit startIndex,pageSize;/* 第一个参数：（当前页-1）*页面大小第二个参数：页面大小0,55,510,5*/sql.append(" order by creationDate desc limit ?,?");int startIndex=(currentPageNo-1)*pageSize;list.add(startIndex);list.add(pageSize);System.out.println("UserDaoImp.getUserList->sql:"+sql);Object[] params = list.toArray();resultSet = BaseDao.execute(connection, preparedStatement, resultSet, sql.toString(), params);while (resultSet.next()){User _user = new User();_user.setId(resultSet.getInt("id"));_user.setUserCode(resultSet.getString("userCode"));_user.setUserName(resultSet.getString("userName"));_user.setGender(resultSet.getInt("gender"));_user.setBirthday(resultSet.getDate("birthday"));_user.setPhone(resultSet.getString("phone"));_user.setUserRole(resultSet.getInt("userRole"));_user.setUserRoleName(resultSet.getString("userRoleName"));userlist.add(_user);}BaseDao.closeResource(null,preparedStatement,resultSet);}return userlist;}

UserService

 //通过条件查询 获取用户列表 userlistpublic List<User> getUserList(String queryUserName, int queryuserRole,int currentPageNo,int pageSize);

UserServiceImp

    //通过条件查询 获取用户列表 userlistpublic List<User> getUserList(String queryUserName, int queryuserRole, int currentPageNo, int pageSize) {Connection connection =null;List<User> userList=null;try {connection = BaseDao.getConnection();userList = userDao.getUserList(connection, queryUserName, queryuserRole, currentPageNo, pageSize);} catch (SQLException e) {e.printStackTrace();}finally {BaseDao.closeResource(connection,null,null);}return userList;}

5.5 获取角色列表

UserDao

public interface RoleDao {//获取角色列表public List<Role> getRoleList(Connection connection)throws SQLException;
}

UserDaoImp

package com.young.dao.Role;import com.young.dao.BaseDao;
import com.young.pojo.Role;import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;public class RoleDaoImp implements RoleDao  {public List<Role> getRoleList(Connection connection) throws SQLException {//获取角色列表PreparedStatement preparedStatement=null;ResultSet resultSet=null;ArrayList<Role> list = new ArrayList<Role>();if(connection!=null){String sql="select * from smbms_role";Object[] params={};resultSet = BaseDao.execute(connection, preparedStatement, resultSet, sql, params);while (resultSet.next()){Role role = new Role();role.setId(resultSet.getInt("id"));role.setRoleCode(resultSet.getString("roleCode"));role.setRoleName(resultSet.getString("roleName"));list.add(role);}BaseDao.closeResource(null,preparedStatement,resultSet);}return list;}
}

UserService

public interface RoleService {//获取角色列表public List<Role> getRoleList();
}

UserServiceImp

package com.young.service.role;import com.young.dao.BaseDao;
import com.young.dao.Role.RoleDao;
import com.young.dao.Role.RoleDaoImp;
import com.young.pojo.Role;
import org.junit.Test;import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;public class RolServiceImp implements RoleService {private RoleDao roleDao;public RolServiceImp() {roleDao = new RoleDaoImp();}public List<Role> getRoleList() {Connection connection = null;List<Role> list = null;try {connection=BaseDao.getConnection();list = roleDao.getRoleList(connection);} catch (SQLException e) {e.printStackTrace();}finally {BaseDao.closeResource(connection,null,null);}return list;}@Testpublic void test(){RolServiceImp rolServiceImp = new RolServiceImp();List<Role> list = rolServiceImp.getRoleList();for (Role role : list) {int s = role.getId();System.out.println(s);}}
}

一个小tip

Object[] params={};
sout.prams.length；// 输出是0

Object[] params=null;
sout.prams.length；// 空指针异常，直接报错

5.6 显示用户的Servlet

步骤：

获取用户前端的数据
根据参数的值判断页面请求是否合法
为实现分页准备
用户列表展示
返回前端

代码：

    //用户管理页面的显示private void query(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//  1.获取用户前端的数据String queryname = req.getParameter("queryname");String queryUserRoletemp = req.getParameter("queryUserRole");String pageIndex = req.getParameter("pageIndex");int queryUserRole=0;//默认的用户角色为全选，用0表示。//  获取用户列表UserServiceImp userService = new UserServiceImp();List<User> userList = null; //为了调用userService里面的getUserList方法做准备// 后面的都是在为getUserList的调用而准备参数//  2.根据参数的值判断页面请求是否合法//  第一次走这个请求，默认在第一页，页面的大小固定int pageSize =5;       //后期可以优化到配置文件中去int currentPageNo=1;   //默认为当前页if(queryname==null){queryname="";      //避免出现空指针异常}if(queryUserRoletemp!=null && !queryUserRoletemp.equals("")){queryUserRole=Integer.parseInt(queryUserRoletemp);}if(pageIndex!=null){currentPageNo=Integer.parseInt(pageIndex);}//  3. 为实现分页准备//获取用户总数int totalCount = userService.getUserCount(queryname, queryUserRole);//计算分页的总页数int totolPageCount = (int) (totalCount / pageSize) + 1;//控制首位页if(currentPageNo<1){currentPageNo=1;}else if(currentPageNo>totolPageCount){currentPageNo=totolPageCount;}//  4. 用户列表展示userList = userService.getUserList(queryname, queryUserRole, currentPageNo, pageSize);// 向前端展示userListreq.setAttribute("userList",userList);// 给前端提供roleList选项RolServiceImp rolServiceImp = new RolServiceImp();List<Role> roleList = rolServiceImp.getRoleList();req.setAttribute("roleList",roleList);// 给前端提供其他需要的数据req.setAttribute("queryUserName",queryname);req.setAttribute("totalPageCount",totolPageCount );req.setAttribute("totalCount",totalCount );req.setAttribute("currentPageNo",currentPageNo );req.setAttribute("queryUserRole",queryUserRole );//  5. 返回前端req.getRequestDispatcher("userlist.jsp").forward(req,resp);}

6.我的总结

6.1 重点

MVC三层架构：

Dao层直接操作数据库，实现增删改查等功能
Service层调用Dao层，完成业务逻辑
Servllet层接收用户的请求，交给业务层处理对应的代码并且控制视图的跳转。

6.2 难点

动态的SQL（ 5.3 UserDaoImpl 代码）
Servlet 的动态获取数据库中的信息，返回到前端（用户角色列表展示部分 5.5 和 5.6 相关部分）

6.3 不足之处

前端知识严重不足，有待提高

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