資料庫：

專案如何搭建？

考慮使用不使用Maven？依賴，jar

專案搭建準備工作

1.搭建一個mavenweb專案

2.配置Tomcat

3.測試專案是否能夠跑起來

4.匯入專案中會遇見的jar包；

jsp,Servlet,mysql驅動，jstl，stand...

5.建立專案包結構

6.編寫實體類；

ORM對映：表-類對映

7.編寫基礎公共類

1. 資料庫配置檔案（db.properties）

   driver=com.mysql.jdbc.Driver
   url=jdbc:mysql://localhost:3306/smbms?userUnicode=true&characterEncoding=utf-8&useSSL=true
    
   

   username=root password=123456

2. 編寫資料公共類

   package com.kuang.dao;
   
   import java.io.IOException;
   import java.io.InputStream;
   import java.sql.*;
   import java.util.Properties;
   
   //操作資料庫的公共類
   public class BaseDao {
   
       private static String driver;
       private static String url;
       private static String username;
       
    
   private static String password;
   
       //靜態程式碼塊，類載入的時候就初始化了
       static {
           Properties properties = new Properties();
           //通過類載入器讀取對應的資源
           InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
   
           try {
               properties.load(is);
           } catch (IOException e) {
               e.printStackTrace();
           }
   
           driver 
    
   = properties.getProperty("driver");
           url = properties.getProperty("url");
           username = properties.getProperty("username");
           password = properties.getProperty("password");
       }
   
       //獲取資料庫的連線
       public static Connection getConnection(){
           Connection connection = null;
           try {
               Class.forName(driver);
               connection = DriverManager.getConnection(url, username, password);
           } catch (Exception e) {
               e.printStackTrace();
           }
           return connection;
       }
   
       //編寫查詢公共類
       public static ResultSet execute(Connection connection,String sql,Object[] params,ResultSet resultSet,PreparedStatement preparedStatement) throws SQLException {
           //預編譯的sql，在後面直接執行就可以了
           preparedStatement = connection.prepareStatement(sql);
   
           for (int i = 0; i < params.length; i++) {
               //setObject,佔位從1開始，但是我們的陣列是從0開始！
               preparedStatement.setObject(i+1,params[i]);
           }
   
           resultSet = preparedStatement.executeQuery();
           return resultSet;
       }
   
       //編寫增刪改公共方法
       public 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++) {
               //setObject,佔位從1開始，但是我們的陣列是從0開始！
               preparedStatement.setObject(i+1,params[i]);
           }
   
           int updateRows = preparedStatement.executeUpdate();
           return updateRows;
       }
   
       //釋放資源
       public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
           boolean flag = true;
   
           if (resultSet!=null){
               try {
                   resultSet.close();
                   //GC回收
                   resultSet = null;
               } catch (SQLException e) {
                   e.printStackTrace();
                   flag = false;
               }
           }
   
           if (preparedStatement!=null){
               try {
                   preparedStatement.close();
                   //GC回收
                   preparedStatement = null;
               } catch (SQLException e) {
                   e.printStackTrace();
                   flag = false;
               }
           }
   
           if (connection!=null){
               try {
                   connection.close();
                   //GC回收
                   connection = null;
               } catch (SQLException e) {
                   e.printStackTrace();
                   flag = false;
               }
           }
   
           return flag;
       }
   
   
   }

3. 編寫字元編碼過濾器

   package com.kuang.filter;
   
   import javax.servlet.*;
   import java.io.IOException;
   
   public class CharacterEncodingFilter implements Filter {
       @Override
       public void init(FilterConfig filterConfig) throws ServletException {
   
       }
   
       @Override
       public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
           servletRequest.setCharacterEncoding("utf-8");
           servletResponse.setCharacterEncoding("utf-8");
           servletResponse.setContentType("text/html;charset=utf-8");
   
           filterChain.doFilter(servletRequest,servletResponse);
       }
   
       @Override
       public void destroy() {
   
       }
   }

       <!--字元編碼過濾器-->
       <filter>
           <filter-name>CharacterEncodingFilter</filter-name>
           <filter-class>com.kuang.filter.CharacterEncodingFilter</filter-class>
       </filter>
       <filter-mapping>
           <filter-name>CharacterEncodingFilter</filter-name>
           <url-pattern>/*</url-pattern>
       </filter-mapping>

8.匯入靜態資源

1.編寫前端頁面

2.設定首頁

    <!--設定歡迎頁面-->
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>

3.編寫dao層登入使用者登入的介面

package com.kuang.dao.user;

import com.kuang.pojo.User;

import java.sql.Connection;
import java.sql.SQLException;

public interface UserDao {

    //得到要登入的使用者
    public User getLoginUser(Connection connection,String userCode) throws SQLException;

}

4.編寫dao介面的實現類

package com.kuang.dao.user;

import com.kuang.dao.BaseDao;
import com.kuang.pojo.User;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ResourceBundle;

public class UserDaoImpl implements UserDao {
    //得到要登入的使用者
    @Override
    public User getLoginUser(Connection connection, String userCode) throws SQLException {

        PreparedStatement pstm = null;
        ResultSet rs = null;
        User user = null;


        if (connection!=null){
            String sql = "select * from smbms_user where userCode=?";
            Object[] params = {userCode};


            rs = BaseDao.execute(connection, pstm, rs, sql, params);

            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"));
            }
            BaseDao.closeResource(null,pstm,rs);

        }
        return user;

    }
}

5.業務層介面

package com.kuang.service.user;

import com.kuang.pojo.User;

public interface UserService {
    //使用者登入
    public User login(String userCode,String password);
}

6.業務層實現類

package com.kuang.service.user;

import com.kuang.dao.BaseDao;
import com.kuang.dao.user.UserDao;
import com.kuang.dao.user.UserDaoImpl;
import com.kuang.pojo.User;
import org.junit.Test;

import java.sql.Connection;
import java.sql.SQLException;

public class UserServiceImpl implements UserService {

    //業務層都會呼叫dao層，所有我們要引入Dao層;
    private UserDao userDao;
    public UserServiceImpl(){
        userDao = new UserDaoImpl();
    }

    @Override
    public User login(String userCode, String password) {
        Connection connection = null;
        User user = null;

        try {
            connection = BaseDao.getConnection();
            //通過業務層呼叫對應的具體的資料庫操作
            user = userDao.getLoginUser(connection, userCode);
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            BaseDao.closeResource(connection,null,null);
        }
        return user;
    }

/*    @Test
    public void test(){
        UserServiceImpl userService = new UserServiceImpl();
        User admin = userService.login("admin", "1234dadfs567");
        System.out.println(admin.getUserPassword());
    }*/
}

7.編寫Servlet

package com.kuang.servlet.user;


import com.kuang.pojo.User;
import com.kuang.service.user.UserServiceImpl;
import com.kuang.util.Constants;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LoginServlet extends HttpServlet {

    //Servlet:控制層呼叫業務層

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        System.out.println("LoginServlet--start....");

        //獲取使用者名稱和密碼
        String userCode = req.getParameter("userCode");
        String userPassword = req.getParameter("userPassword");

        //和資料庫中的密碼進行對比，呼叫業務層；
        UserServiceImpl userService = new UserServiceImpl();
        User user = userService.login(userCode, userPassword); //這裡已經把登入的人給查出來了

        if (user!=null){//查有此人，可以登入
            //將使用者的資訊放到Session中；
            req.getSession().setAttribute(Constants.USER_SESSION,user);
            //跳轉到內部主頁
            resp.sendRedirect("jsp/frame.jsp");
        }else {//查無此人，無法登入
            //轉發回登陸頁面，順帶提示它，使用者名稱或者密碼錯誤；
            req.setAttribute("error","使用者名稱或者密碼不正確");
            req.getRequestDispatcher("login.jsp").forward(req,resp);
            
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

8.註冊Servlet

    <!--Servlet-->
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>com.kuang.servlet.user.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login.do</url-pattern>
    </servlet-mapping>

9.測試訪問，確保以上功能成功！

登入功能優化

註冊功能：

思路：移除Session，返回登入頁面

package com.kuang.servlet.user;

import com.kuang.util.Constants;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LogoutServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //移除使用者的Constants.USER_SESSION
        req.getSession().removeAttribute(Constants.USER_SESSION);
        resp.sendRedirect("/login.jsp");//返回登入頁面
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

在xml中註冊

<servlet>
        <servlet-name>LogoutServlet</servlet-name>
        <servlet-class>com.kuang.servlet.user.LogoutServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LogoutServlet</servlet-name>
        <url-pattern>/jsp/logout.do</url-pattern>
    </servlet-mapping>

登入攔截優化

編寫一個過濾器，並註冊

package com.kuang.filter;

import com.kuang.pojo.User;
import com.kuang.util.Constants;
import org.junit.runner.Request;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class SysFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) resp;

        //過濾器，從Session中獲取使用者
        User user = (User) request.getSession().getAttribute(Constants.USER_SESSION);

        if (user==null){//已經被移除或者登出了，或者未登入
            response.sendRedirect("/smbms/error.jsp");
        }else {
            filterChain.doFilter(req,resp);
        }
    }

    @Override
    public void destroy() {

    }
}

    <!--使用者登入過濾器-->
    <filter>
        <filter-name>SysFilter</filter-name>
        <filter-class>com.kuang.filter.SysFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>SysFilter</filter-name>
        <url-pattern>/jsp/*</url-pattern>
    </filter-mapping>

測試，登入，登出，許可權，都要保證實現

密碼修改

1.匯入前端素材

<li><a href="${pageContext.request.contextPath }/jsp/pwdmodify.jsp">密碼修改</a></li>

2.寫專案，建議從底層向上寫

3.UserDao 介面

    //修改當前使用者密碼
    public int updatePwd(Connection connection,int id,String password) throws SQLException;

4.UserDao 介面實現類

    //修改當前使用者密碼
    @Override
    public int updatePwd(Connection connection, int id, String password) throws SQLException {
        System.out.println("UserServlet"+password);
        PreparedStatement pstm = null;
        int execute = 0;

        if (connection!=null){
            String sql = "update smbms_user set userPassword = ? where id = ?";
            Object params[] = {password,id};
            execute = BaseDao.execute(connection, pstm, sql, params);
            BaseDao.closeResource(null,pstm,null);
        }

        return execute;

    }

5.UserService層

    //根據使用者ID修改密碼
    public boolean updatePwd(int id, String pwd);

6.UserService實現類

@Override
    public boolean updatePwd(int id, String pwd) {
        System.out.println("UserServlet"+pwd);
        Connection connection = null;
        boolean flag = false;
        //修改密碼
        try {
            connection = BaseDao.getConnection();
            if (userDao.updatePwd(connection,id,pwd)>0){
                flag = true;
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            BaseDao.closeResource(connection,null,null);
        }
        return flag;
    }

7.記得實現複用，需要提取出方法！

@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String method = req.getParameter("method");
        if (method.equals("savepwd")&&method!=null){
            this.updatePwd(req,resp);
        }
    }

public void updatePwd(HttpServletRequest req, HttpServletResponse resp){
        //從Session裡面拿ID；
        Object o = req.getSession().getAttribute(Constants.USER_SESSION);
        String newpassword = req.getParameter("newpassword");

        System.out.println("UserServlet"+newpassword);

        boolean flag = false;

        if (o!=null && newpassword!=null){
            UserService userService = new UserServiceImpl();
            flag = userService.updatePwd(((User) o).getId(), newpassword);
            if (flag){
                req.setAttribute("message","修改密碼成功，請退出，使用新密碼登入");
                //密碼修改成功，移除當前Session
                req.getSession().removeAttribute(Constants.USER_SESSION);
            }else {
                req.setAttribute("message","密碼修改失敗");
            }
        }else {
            req.setAttribute("message","新密碼有問題");
        }
        try {
            req.getRequestDispatcher("pwdmodify.jsp").forward(req,resp);
        } catch (ServletException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

註冊Servlet

<servlet>
        <servlet-name>UserServlet</servlet-name>
        <servlet-class>com.kuang.servlet.user.UserServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>UserServlet</servlet-name>
        <url-pattern>/jsp/user.do</url-pattern>
    </servlet-mapping>

8.測試

優化密碼修改使用Ajax；

1.阿里巴巴的fastjson

<!-- https://mvnrepository.com/artifact/com.alibaba/fastjson -->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.75</version>
</dependency>

2.後臺程式碼修改

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String method = req.getParameter("method");
        if (method.equals("savepwd")&&method!=null){
            this.updatePwd(req,resp);
        }else if (method.equals("pwdmodify")&&method!=null){
            this.pwdModify(req,resp);
        }
    }

 //驗證舊密碼,session中有使用者的密碼
    public void pwdModify(HttpServletRequest req, HttpServletResponse resp){
        //從Session裡面拿ID
        Object o = req.getSession().getAttribute(Constants.USER_SESSION);
        String oldpassword = req.getParameter("oldpassword");

        //萬能的Map ：結果集
        Map<String, String> resultMap = new HashMap<String, String>();
        if (o==null) { //Session失效了,session過期了
            resultMap.put("result","sessionerror");
        }else if (StringUtils.isNullOrEmpty(oldpassword)){ //輸入的密碼為空
            resultMap.put("result","error");
        }else {
            String userPassword = ((User) o).getUserPassword();//Session中使用者的密碼
            if (oldpassword.equals(userPassword)){
                resultMap.put("result","true");
            }else {
                resultMap.put("result","false");
            }
        }


        try {
            resp.setContentType("application/json");
            PrintWriter writer = resp.getWriter();
            //JSONArray 阿里巴巴的JSON工具類，轉換格式21.
            /*
             resultMap = ["result","sessionerror","result","error"]
             Json格式 = {key : value}
            */
            writer.write(JSONArray.toJSONString(resultMap));
            writer.flush();
            writer.close();
        } catch (IOException e) {
            e.printStackTrace();
        }


    }

3.測試

使用者管理實現

思路：

1.匯入分頁的工具類

2.使用者列表使用者匯入

userlist.jsp

rollpage.jsp

1、獲取使用者數量

1.UserDao

    //根據使用者名稱或者角色查詢使用者總數
    public int getUserCount(Connection connection,String username,int userRole) throws SQLException;

2.UserDaoImpl

//根據使用者名稱或者角色查詢使用者總數【最難理解的SQL】
    @Override
    public int getUserCount(Connection connection, String username, int userRole) throws SQLException {

        PreparedStatement pstm = null;
        ResultSet rs = null;
        int count = 0;

        if (connection!=null){
            StringBuffer sql = new StringBuffer();
            sql.append("select count(1) as count from smbms_user u,smbms_role r where u.userRole = r.id");
            ArrayList<Object> list = new ArrayList<Object>();//存放我們的引數

            if (!StringUtils.isNullOrEmpty(username)){
                sql.append(" and u.userName like ?");
                list.add("%"+username+"%");//index:0
            }

            if (userRole>0){
                sql.append(" and u.userRole = ?");
                list.add(userRole);//index:1
            }

            //怎麼把list轉換為資料
            Object[] params = list.toArray();

            System.out.println("UserDaoImpl->getUserCount:"+sql.toString());//輸出最後完整的SQL語句

            rs = BaseDao.execute(connection, pstm, rs, sql.toString(), params);

            if (rs.next()){
                count = rs.getInt("count");//從結果中獲取最終的數量
            }
            BaseDao.closeResource(null,pstm,rs);
        }
        return count;

    }

3.UserService

//查詢記錄數
    public int getUserCount(String username,int userRole);

4.UserServiceImpl

    @Override
    public int getUserCount(String username, int userRole) {

        Connection connection = null;
        int count = 0;
        try {
            connection = BaseDao.getConnection();
            count = userDao.getUserCount(connection, username, userRole);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally{
            BaseDao.closeResource(connection,null,null);
        }

        return count;

    }

2、獲取使用者列表

1.userdao

    //通過條件查詢-userList
    public List<User> getUserList(Connection connection,String userName,int userRole,int currentPageNo,int pageSize)throws Exception;

2.userdaoImpl

@Override
    public List<User> getUserList(Connection connection, String userName, int userRole, int currentPageNo, int pageSize) throws Exception {
        PreparedStatement pstm = null;
        ResultSet rs = null;
        List<User> userList = new ArrayList<>();
        if (connection !=null) {
            StringBuffer sql = new StringBuffer();
            sql.append("select u.*,r.roleName as useRoleName from smbms_user u,smbms_role r where u.userRole = r.roleCode");
            List<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");
            }
            sql.append(" order by creationDate limit ?,?");
            currentPageNo = (currentPageNo-1)*pageSize;
            list.add(currentPageNo);
            list.add(pageSize);

            Object[] params = list.toArray();
            System.out.println("sql ----> " + sql.toString());
            rs = BaseDao.execute(connection, pstm, rs, sql.toString(), params);
            while(rs.next()){
                User _user = new User();
                _user.setId(rs.getInt("id"));
                _user.setUserCode(rs.getString("userCode"));
                _user.setUserName(rs.getString("userName"));
                _user.setGender(rs.getInt("gender"));
                _user.setBirthday(rs.getDate("birthday"));
                _user.setPhone(rs.getString("phone"));
                _user.setUserRole(rs.getInt("userRole"));
                _user.setUserRoleName(rs.getString("userRoleName"));
                userList.add(_user);
            }
            BaseDao.closeResource(null,pstm,rs);
        }
        return userList;

    }

3.userService

    //根據條件查詢使用者列表
    public List<User> getUserList(String queryUserName,int queryUserRole,int currentPageNo,int pageSize);

4.userServiceImpl

@Override
    public List<User> getUserList(String queryUserName, int queryUserRole, int currentPageNo, int pageSize) {
        Connection connection = null;
        List<User> userList = null;
        System.out.println("queryUserName ---- > " + queryUserName);
        System.out.println("queryUserRole ---- > " + queryUserRole);
        System.out.println("currentPageNo ---- > " + currentPageNo);
        System.out.println("pageSize ---- > " + pageSize);
        try {
            connection = BaseDao.getConnection();
            userList = userDao.getUserList(connection, queryUserName, queryUserRole, currentPageNo, pageSize);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            BaseDao.closeResource(connection,null,null);
        }
        return userList;
    }

3、獲取角色操作

為了我們職責統一，可以把角色的操作單獨放在一個包中，和POJO類對應

RoleDao

package com.kuang.dao.role;

import com.kuang.pojo.Role;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

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

RoleDaoImpl

package com.kuang.dao.role;

import com.kuang.dao.BaseDao;
import com.kuang.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 RoleDaoImpl implements RoleDao {
    //獲取角色列表
    @Override
    public List<Role> getRoleList(Connection connection) throws SQLException {

        PreparedStatement pstm =null;
        ResultSet resultSet = null;
        ArrayList<Role> roleList = new ArrayList<Role>();
        if (connection!=null){
            String sql = "select * from smbms_role";
            Object[] params = {};
            resultSet = BaseDao.execute(connection, pstm, 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"));
                roleList.add(_role);
            }
            BaseDao.closeResource(null,pstm,resultSet);
        }
        return roleList;
    }
}

RoleService

package com.kuang.service.role;

import com.kuang.pojo.Role;

import java.util.List;

public interface RoleService {
    public List<Role> getRoleList();
}

RoleServiceImpl

package com.kuang.service.role;

import com.kuang.dao.BaseDao;
import com.kuang.dao.role.RoleDao;
import com.kuang.dao.role.RoleDaoImpl;
import com.kuang.pojo.Role;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

public class RoleServiceImpl implements RoleService {

    //引用Dao
    private RoleDao roleDao;
    public RoleServiceImpl(RoleDao roleDao) {
        roleDao = new RoleDaoImpl();
    }

    @Override
    public List<Role> getRoleList() {
        Connection connection = null;
        List<Role> roleList = null;
        try {
            connection = BaseDao.getConnection();
            roleList = roleDao.getRoleList(connection);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            BaseDao.closeResource(connection,null,null);
        }
        return roleList;
    }
}

4.使用者顯示的Servlet

1.獲取使用者端的資料（查詢）

2.判斷請求是否需要執行，看引數的值判斷

3.為了實現分頁，需要計算出當前頁面和總頁面以及頁面大小...

4.使用者列表展示

5.返回前端

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }

    //重點、難點
    public void query(HttpServletRequest req, HttpServletResponse resp){

        //查詢使用者列表

        //從前端獲取資料
        String queryUserName = req.getParameter("queryname");
        String temp = req.getParameter("queryUserRole");
        String pageIndex = req.getParameter("pageIndex");
        int queryUserRole = 0;

        //獲取使用者列表
        UserServiceImpl userService = new UserServiceImpl();
        List<User> userList = null;

        //第一次走這個請求，一定是第一頁，頁面大小固定的
        int pageSize =5; //可以把這個寫到配置檔案中，方便後期修改；
        int currentPageNo = 1;

        if (queryUserName == null){
            queryUserName = "";
        }
        if (temp!=null && !temp.equals("")){
            queryUserRole = Integer.parseInt(temp);  //給查詢賦值0，1，2，3
        }
        if (pageIndex!=null){

                currentPageNo = Integer.parseInt(pageIndex);

        }

        //獲取使用者的總數（分頁： 上一頁，下一頁的情況）
        int totalCount = userService.getUserCount(queryUserName, queryUserRole);
        //總頁數支援
        PageSupport pageSupport = new PageSupport();
        pageSupport.setCurrentPageNo(currentPageNo);
        pageSupport.setPageSize(pageSize);
        pageSupport.setTotalCount(totalCount);

        int totalPageCount = ((int)(totalCount/pageSize))+1; //總共有幾頁

        //控制首頁和尾頁
        //如果頁面要小於一了，就顯示第一頁的東西
        if (currentPageNo<1){
            currentPageNo = 1;
        }else if (currentPageNo>totalPageCount){//當前頁面大於最後一頁；
            currentPageNo = totalPageCount;
        }

        //獲取使用者列表展示
        userList = userService.getUserList(queryUserName, queryUserRole, currentPageNo, pageSize);
        req.setAttribute("userList",userList);

        RoleServiceImpl roleService = new RoleServiceImpl();
        List<Role> roleList = roleService.getRoleList();
        req.setAttribute("roleList",roleList);
        req.setAttribute("totalCount",totalCount);
        req.setAttribute("currentPageNo",currentPageNo);
        req.setAttribute("totalPageCount",totalPageCount);
        req.setAttribute("queryUserName",queryUserName);
        req.setAttribute("queryUserRole",queryUserRole);

        //返回前端
        try {
            req.getRequestDispatcher("userlist.jsp").forward(req,resp);
        } catch (ServletException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

小黃鴨除錯法