SMBMS

 

 

 数据库：

 

 

 项目如何搭建？

考虑使用不使用Maven？依赖，jar

项目搭建准备工作

1.搭建一个mavenweb项目

2.配置Tomcat

3.测试项目是否能够跑起来

4.导入项目中会遇见的jar包；

jsp,Servlet,mysql驱动，jstl，stand...

5.创建项目包结构

 

 

 

6.编写实体类；

ORM映射：表-类映射

7.编写基础公共类

1. 数据库配置文件（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. 编写数据公共类

   package com.kuang.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 {
           Properties properties = new Properties();
           //通过类加载器读取对应的资源
           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");
       }
   
       //获取数据库的连接
       public static Connection getConnection(){
           Connection connection = null;
           try {
               Class.forName(driver);
               connection = DriverManager.getConnection(url, username, password);
           } catch (Exception e) {
               e.printStackTrace();
           }
           return connection;
       }
   
       //编写查询公共类
       public static ResultSet execute(Connection connection,String sql,Object[] params,ResultSet resultSet,PreparedStatement preparedStatement) throws SQLException {
           //预编译的sql，在后面直接执行就可以了
           preparedStatement = connection.prepareStatement(sql);
   
           for (int i = 0; i < params.length; i++) {
               //setObject,占位从1开始，但是我们的数组是从0开始！
               preparedStatement.setObject(i+1,params[i]);
           }
   
           resultSet = preparedStatement.executeQuery();
           return resultSet;
       }
   
       //编写增删改公共方法
       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,占位从1开始，但是我们的数组是从0开始！
               preparedStatement.setObject(i+1,params[i]);
           }
   
           int updateRows = preparedStatement.executeUpdate();
           return updateRows;
       }
   
       //释放资源
       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. 编写字符编码过滤器

   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() {
   
       }
   }

       <!--字符编码过滤器-->
       <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.导入静态资源

 

 

1.编写前端页面

2.设置首页

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

3.编写dao层登录用户登录的接口

package com.kuang.dao.user;

import com.kuang.pojo.User;

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

public interface UserDao {

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

}

4.编写dao接口的实现类

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 {
    //得到要登录的用户
    @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.业务层接口

package com.kuang.service.user;

import com.kuang.pojo.User;

public interface UserService {
    //用户登录
    public User login(String userCode,String password);
}

 

6.业务层实现类

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 {

    //业务层都会调用dao层，所有我们要引入Dao层;
    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;
    }

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

7.编写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:控制层调用业务层

    @Override
    protected 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；
        UserServiceImpl userService = new UserServiceImpl();
        User user = userService.login(userCode, userPassword); //这里已经把登录的人给查出来了

        if (user!=null){//查有此人，可以登录
            //将用户的信息放到Session中；
            req.getSession().setAttribute(Constants.USER_SESSION,user);
            //跳转到内部主页
            resp.sendRedirect("jsp/frame.jsp");
        }else {//查无此人，无法登录
            //转发回登陆页面，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);
            
        }

    }

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

8.注册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.测试访问，确保以上功能成功！

登录功能优化

注册功能：

思路：移除Session，返回登录页面

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 {
        //移除用户的Constants.USER_SESSION
        req.getSession().removeAttribute(Constants.USER_SESSION);
        resp.sendRedirect("/login.jsp");//返回登录页面
    }

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

在xml中注册

<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>

登录拦截优化

 编写一个过滤器，并注册

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;

        //过滤器，从Session中获取用户
        User user = (User) request.getSession().getAttribute(Constants.USER_SESSION);

        if (user==null){//已经被移除或者注销了，或者未登录
            response.sendRedirect("/smbms/error.jsp");
        }else {
            filterChain.doFilter(req,resp);
        }
    }

    @Override
    public void destroy() {

    }
}

    <!--用户登录过滤器-->
    <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>

测试，登录，注销，权限，都要保证实现

密码修改 

1.导入前端素材

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

2.写项目，建议从底层向上写

 

 

 3.UserDao 接口

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

 

4.UserDao 接口实现类

    //修改当前用户密码
    @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层

    //根据用户ID修改密码
    public boolean updatePwd(int id, String pwd);

6.UserService实现类

@Override
    public boolean updatePwd(int id, String pwd) {
        System.out.println("UserServlet"+pwd);
        Connection connection = null;
        boolean flag = false;
        //修改密码
        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.记得实现复用，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){
        //从Session里面拿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","修改密码成功，请退出，使用新密码登录");
                //密码修改成功，移除当前Session
                req.getSession().removeAttribute(Constants.USER_SESSION);
            }else {
                req.setAttribute("message","密码修改失败");
            }
        }else {
            req.setAttribute("message","新密码有问题");
        }
        try {
            req.getRequestDispatcher("pwdmodify.jsp").forward(req,resp);
        } catch (ServletException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

注册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.测试

 

优化密码修改使用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.后台代码修改

    @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);
        }
    }

 

 //验证旧密码,session中有用户的密码
    public void pwdModify(HttpServletRequest req, HttpServletResponse resp){
        //从Session里面拿ID
        Object o = req.getSession().getAttribute(Constants.USER_SESSION);
        String oldpassword = req.getParameter("oldpassword");

        //万能的Map ：结果集
        Map<String, String> resultMap = new HashMap<String, String>();
        if (o==null) { //Session失效了,session过期了
            resultMap.put("result","sessionerror");
        }else if (StringUtils.isNullOrEmpty(oldpassword)){ //输入的密码为空
            resultMap.put("result","error");
        }else {
            String userPassword = ((User) o).getUserPassword();//Session中用户的密码
            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工具类，转换格式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.测试

 

用户管理实现

思路：

 

 1.导入分页的工具类

2.用户列表用户导入

 

userlist.jsp

rollpage.jsp

1、获取用户数量

1.UserDao

    //根据用户名或者角色查询用户总数
    public int getUserCount(Connection connection,String username,int userRole) throws SQLException;

 

2.UserDaoImpl

//根据用户名或者角色查询用户总数【最难理解的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>();//存放我们的参数

            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
            }

            //怎么把list转换为数据
            Object[] params = list.toArray();

            System.out.println("UserDaoImpl->getUserCount:"+sql.toString());//输出最后完整的SQL语句

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

            if (rs.next()){
                count = rs.getInt("count");//从结果中获取最终的数量
            }
            BaseDao.closeResource(null,pstm,rs);
        }
        return count;

    }

 

3.UserService

//查询记录数
    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、获取用户列表

1.userdao

    //通过条件查询-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

    //根据条件查询用户列表
    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、获取角色操作

为了我们职责统一，可以把角色的操作单独放在一个包中，和POJO类对应

 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 {
    //获取角色列表
    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 {
    //获取角色列表
    @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.用户显示的Servlet

1.获取用户端的数据（查询）

2.判断请求是否需要执行，看参数的值判断

3.为了实现分页，需要计算出当前页面和总页面以及页面大小...

4.用户列表展示

5.返回前端

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

    //重点、难点
    public void query(HttpServletRequest req, HttpServletResponse resp){

        //查询用户列表

        //从前端获取数据
        String queryUserName = req.getParameter("queryname");
        String temp = req.getParameter("queryUserRole");
        String pageIndex = req.getParameter("pageIndex");
        int queryUserRole = 0;

        //获取用户列表
        UserServiceImpl userService = new UserServiceImpl();
        List<User> userList = null;

        //第一次走这个请求，一定是第一页，页面大小固定的
        int pageSize =5; //可以把这个写到配置文件中，方便后期修改；
        int currentPageNo = 1;

        if (queryUserName == null){
            queryUserName = "";
        }
        if (temp!=null && !temp.equals("")){
            queryUserRole = Integer.parseInt(temp);  //给查询赋值0，1，2，3
        }
        if (pageIndex!=null){

                currentPageNo = Integer.parseInt(pageIndex);

        }

        //获取用户的总数（分页： 上一页，下一页的情况）
        int totalCount = userService.getUserCount(queryUserName, queryUserRole);
        //总页数支持
        PageSupport pageSupport = new PageSupport();
        pageSupport.setCurrentPageNo(currentPageNo);
        pageSupport.setPageSize(pageSize);
        pageSupport.setTotalCount(totalCount);

        int totalPageCount = ((int)(totalCount/pageSize))+1; //总共有几页

        //控制首页和尾页
        //如果页面要小于一了，就显示第一页的东西
        if (currentPageNo<1){
            currentPageNo = 1;
        }else if (currentPageNo>totalPageCount){//当前页面大于最后一页；
            currentPageNo = totalPageCount;
        }

        //获取用户列表展示
        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();
        }

    }

小黄鸭调试法