SMBMS(超市订单管理系统)

代码：（建议把静态资源和sql拿过来用，其他自己写一遍练手。注意修改相关配置文件。）

链接:https://pan.baidu.com/s/12MmpF9msJVjLT1U77XYfRw
提取码:11fv

数据库：

项目如何搭建？

考虑是不是用Maven？依赖, jar包.

1.项目搭建准备工作

1. 搭建一个maven web 项目.
2. 配置Tomcat.
3. 测试项目是否能够跑起来.
4. Pom.xml 中导入项目中需要的jar包.(jsp，Servlet，mysql驱动，jstl，standard…)

<dependencies>
  <dependency>
    <groupId>junitgroupId>
    <artifactId>junitartifactId>
    <version>4.12version>
  dependency>
  
  <dependency>
    <groupId>javax.servletgroupId>
    <artifactId>javax.servlet-apiartifactId>
    <version>4.0.1version>
  dependency>
  
  <dependency>
    <groupId>javax.servlet.jspgroupId>
    <artifactId>javax.servlet.jsp-apiartifactId>
    <version>2.3.3version>
  dependency>
  
  <dependency>
    <groupId>mysqlgroupId>
    <artifactId>mysql-connector-javaartifactId>
    <version>5.1.47version>
  dependency>
  
  <dependency>
    <groupId>javax.servlet.jsp.jstlgroupId>
    <artifactId>jstl-apiartifactId>
    <version>1.2version>
  dependency>
  
  <dependency>
    <groupId>taglibsgroupId>
    <artifactId>standardartifactId>
    <version>1.1.2version>
  dependency>
  
  <dependency>
    <groupId>com.alibabagroupId>
    <artifactId>fastjsonartifactId>
    <version>1.2.80version>
  dependency>
dependencies>

5. 创建项目包结构.

6. 编写实体类.(pojo)
   ROM映射:表—类映射.

7. 编写基础公共类.

   1、数据库配置文件：

driver = com.mysql.jdbc.Driver
url = jdbc:mysql://localhost:3306/smbms?useUnicode=true&characterEncoding=utf8&useSSL=true
username = root
password = newpass

​ 2、编写数据库的公共类：

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");
    }

  
    //获取数据库的链接。
    public static Connection getConnection(){
        Connection connection = null;
        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url,username,password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return connection;
    }

  
    //编写查询工具类。
    public 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++) {
            //setObject,占位符从1开始，但是我们的数组是从0开始的。
            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,PreparedStatement preparedStatement,String sql,Object[] params) throws SQLException {
        preparedStatement = connection.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
            //setObject,占位符从1开始，但是我们的数组是从0开始的。
            preparedStatement.setObject(i+1,params[i]);
        }
        int updateRows = preparedStatement.executeUpdate();
        return updateRows;
    }

  
    //释放资源。
    public static  boolean closeResourse(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet){
        boolean flag = true;
        if (resultSet != null){
            try {
                resultSet.close();
                //GC回收
                resultSet = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        if (preparedStatement != null){
            try {
                preparedStatement.close();
                //GC回收
                preparedStatement = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        if (connection != null){
            try {
                connection.close();
                //GC回收
                connection = null;
            } catch (SQLException throwables) {
                throwables.printStackTrace();
                flag = false;
            }
        }
        return false;
    }

}

​ 3、编写字符编码过滤器(别忘了注册过滤器)

package com.kuang.filter;

import javax.servlet.*;
import java.io.IOException;

public class CharacterEncodingFilter implements Filter {//别导错包。

    @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");

        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {

    }
}

<filter>
    <filter-name>CharacterEncodingFilterfilter-name>
    <filter-class>com.kuang.filter.CharacterEncodingFilterfilter-class>
filter>
<filter-mapping>
    <filter-name>CharacterEncodingFilterfilter-name>
    <url-pattern>/*url-pattern>
filter-mapping>

8. 导入静态资源 (js,css,img,calendar)

2.登录功能实现

1. 编写前端页面(直接拿jsp过来用)
2. 设置首页

<welcome-file-list>
    <welcome-file>login.jspwelcome-file>
welcome-file-list>

3. 编写dao层登录用户登录的接口

//通过userCode和userPassword，得到要登陆的用户。
public User getLoginUser(Connection connection,String userCode,String userPassword) throws SQLException;

4. 编写dao层接口的实现类

//通过userCode和userPassword，得到要登陆的用户。
@Override
public User getLoginUser(Connection connection, String userCode,String userPassword) throws SQLException {
    PreparedStatement pstm = null;
    ResultSet rs = null;
    User user = null;

    if (connection!=null){
        String sql = "select * from smbms_user where userCode = ? and userPassword = ?";
        Object[] params = {userCode,userPassword};
        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.closeResourse(null,pstm,rs);
    }
    return user;
}

5. 业务层接口

//用户登录.
public User login(String userCode,String userPassword);

6. 业务层实现类

//业务层都会调用dao层，所以我们要引入Dao层。
private UserDao userDao;
public UserServiceImpl() {//无参构造器。
    userDao = new UserDaoImpl();
}


//用户登录
@Override
public User login(String userCode, String userPassword) {
    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,userPassword);
    } catch (SQLException throwables) {
        throwables.printStackTrace();
    }finally {
        BaseDao.closeResourse(connection,null,null);
    }
    return user;
}

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;

//Servlet：控制层，调用业务层代码。
public class LoginServlet extends HttpServlet {

    @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);//这里已经把登陆的人查出来了。

        if (user!=null){//查有此人，可以登陆。
            //将用户的信息放到Session中；
            req.getSession().setAttribute(Constants.USER_SESSION,user);
            //跳转到主页。
            resp.sendRedirect("jsp/frame.jsp");
        }else {//查无此人,无法登陆。
            //转发回登陆页面，顺带提示它，用户名或者密码错误。
            req.setAttribute("error","用户名或者密码错误！");
            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-name>LoginServletservlet-name>
    <servlet-class>com.kuang.servlet.user.LoginServletservlet-class>
servlet>
<servlet-mapping>
    <servlet-name>LoginServletservlet-name>
    <url-pattern>/login.dourl-pattern>
servlet-mapping>

9. 测试访问,保证以上功能可以成功

3.登录功能优化

注销功能:

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(req.getContextPath()+"/login.jsp");//返回登陆页面。
    }

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

注册xml:

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

4.登录拦截优化

使用户不能直接进入登陆成功的页面。

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 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 Chain) 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，或者为登陆。
            response.sendRedirect("/SMBMS/error.jsp");
        }else{
            Chain.doFilter(req,resp);
        }
    }

    @Override
    public void destroy() {}
  
}

注册xml

<filter>
    <filter-name>SysFilterfilter-name>
    <filter-class>com.kuang.filter.SysFilterfilter-class>
filter>
<filter-mapping>
    <filter-name>SysFilterfilter-name>
    <url-pattern>/jsp/*url-pattern>
filter-mapping>

测试，登录，注销，权限，都要保证OK.

5.密码修改

1. 导入前端素材

密码修改

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 {
    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.closeResourse(null,pstm,null);
    }
    return execute;
}

5. UserService层

//根据用户id修改密码。
public boolean updatePwd(int id,String password)throws SQLException;

6. UserService实现类

//根据用户id修改密码。
@Override
public boolean updatePwd(int id, String pwd) throws SQLException {
    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.closeResourse(connection,null,null);
    }
    return flag;
}

7. servlet记得实现复用，要提取出方法！

//实现Servlet复用
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    String method = req.getParameter("method");
    if (method.equals("savepwd")){
            this.updatePwd(req,resp);
        }else if (method.equals("pwdmodify")){
            this.pwdModify(req,resp);
        }else if (method.equals("query")){
            this.query(req,resp);
        }else if (method.equals("add")){
            this.add(req,resp);
        }else if (method.equals("modifyexe")){
            this.modify(req,resp);
        }else if (method.equals("deluser")){
            this.delUser(req,resp);
        }else if (method.equals("ucexist")){
            this.userCodeExist(req, resp);
        }else if (method.equals("getrolelist")){
            this.getRoleList(req, resp);
        }else if (method.equals("view")){
            this.getUserById(req,resp,"userview.jsp");
        }else if (method.equals("modify")){
            this.getUserById(req,resp,"usermodify.jsp");
        }
}


//修改密码
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");

    boolean flag = false;

    if (o!=null && !StringUtils.isNullOrEmpty(newpassword)){
        UserServiceImpl userService = new UserServiceImpl();

        try {
            flag = userService.updatePwd(((User)o).getId(),newpassword);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }

        if (flag){
            req.setAttribute("message","修改密码成功，请退出，使用新密码登陆！");
            //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xml

<servlet>
    <servlet-name>UserServletservlet-name>
    <servlet-class>com.kuang.servlet.user.UserServletservlet-class>
servlet>
<servlet-mapping>
    <servlet-name>UserServletservlet-name>
    <url-pattern>/jsp/user.dourl-pattern>
servlet-mapping>

8. 测试

6.优化密码修改使用Ajax

1. 阿里巴巴的fastjson（导入）

<dependency>
  <groupId>com.alibabagroupId>
  <artifactId>fastjsonartifactId>
  <version>1.2.80version>
dependency>

2. 后台代码修改

//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。
        /*
        resultMap = ["reslut","sessionerror","reslut","error"]
        Json格式 = {key:value}
         */
        writer.write(JSONArray.toJSONString(resultMap));
        writer.flush();
        writer.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

3. 测试

7.用户管理实现

1. 导入分页的工具类——PageSupport
2. 用户列表页面导入——userlist.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 = ?");
            list.add("%"+username+"%");//index:0   模糊查询。
        }

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

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

        System.out.println("getUserCount的sql语句："+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");//从结果集中获取最终的参数。
        }
        BaseDao.closeResourse(null,pstm,rs);
    }
    return count;
}

3. UserService

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

4. UserServiceImpl

//查询记录数。
@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.closeResourse(connection,null,null);
    }
    return count;
}

2、获取用户列表

1. UserDao

//通过条件查询用户。（分页）
public List<User> getUserList(Connection connection, String userName, int userRole, int currentPageNo, int pageSize) throws Exception;

2. UserDaoImpl

//通过条件查询用户。（分页）
@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<User>();

    if (connection != null) {
        StringBuffer sql = new StringBuffer();
        sql.append("select u.*,r.roleName as userRoleName from smbms_user u,smbms_role r where u.userRole = r.id");
        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);
        }

        //在mysql数据库中，分页使用 limit startIndex，pageSize ; 总数
        sql.append(" order by creationDate DESC limit ?,?");
        currentPageNo = (currentPageNo - 1) * pageSize;
        list.add(currentPageNo);
        list.add(pageSize);

        Object[] params = list.toArray();
        System.out.println("getUserList的sql语句：" + 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.closeResourse(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

//根据条件查询用户列表
@Override
public 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 (Exception e) {
        e.printStackTrace();
    } finally {
        BaseDao.closeResourse(connection, null, null);
    }
    return userList;
}

3、获取角色操作

为了我们的职责统一，我们可以把角色的操作单独放在一个包中，和pojo类对应。

1. RoleDao

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

2. RoleDaoIpml

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<>();

        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.closeResourse(null,pstm,resultSet);
        }
        return rolelist;
    }
}

3. RoleService

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

4. RoleServiceIpml

public class RoleServiceImpl implements RoleService{

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

    //获取角色列表。
    @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.closeResourse(connection,null,null);
        }
        return roleList;
    }

}

4、用户显示的Servlet

1. 获取用户前端的数据（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，页面大小。
4. 用户列表展示。
5. 返回前端。

//查询用户列表（重点，难点）。
public  void query(HttpServletRequest req, HttpServletResponse resp){

    //从前端获取数据：
    String queryUserName = req.getParameter("queryname");
    String temp = req.getParameter("queryUserRole");
    String pageIndex = req.getParameter("pageIndex");//默认为1.
    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;//可以把这个配置到配置文件中，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);
    }

    //获取用户的总量（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 = pageSupport.getTotalPageCount();//总共有几页。

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

建议：小黄鸭调试法：自言自语.

项目原理流程图：

剩下的两个模块的代码直接CV过来改了改bug加了上去（懒得写了！）