Java 简单的用户管理系统（代码注释超全超详细！！！）

Posted 2021-10-20 来一杯Java咖啡

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1.简介

本项目是个java开发的简单的用户管理系统，因为能力有限，我做的界面丑陋了些，大家见谅

实现的功能：登录、添加用户、修改用户（修改的时候用户原始数据显示到界面上、单个删除用户和多个删除用户、数据的分页和跳转、url过滤器

因为我写的时候是开了两个tomcat服务器将图片存储到另一个服务器上进行访问大家这里有疑问的也欢迎咨询哈同时如果有小伙伴想要项目源文件的欢迎加qq群

2.准备工作

1.1开发工具

IDEA2019、SQLYog 、HBuilder

1.2使用语言

SQL、Java、html、JSP

1.3前端框架

BootStrap

1.4导入的jar包

3.项目文件结构

4.代码

sql

/*
SQLyog Ultimate v13.1.1 (64 bit)
mysql - 5.7.29 : Database - contact_sys
*********************************************************************
*/

/*!40101 SET NAMES utf8 */;

/*!40101 SET SQL_MODE=''*/;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`contact_sys` /*!40100 DEFAULT CHARACTER SET utf8 */;

USE `contact_sys`;

/*Table structure for table `client` */

DROP TABLE IF EXISTS `client`;

CREATE TABLE `client` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(32) DEFAULT NULL,
  `password` varchar(32) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

/*Data for the table `client` */

insert  into `client`(`id`,`username`,`password`) values 
(1,'张三','123456');

/*Table structure for table `contact` */

DROP TABLE IF EXISTS `contact`;

CREATE TABLE `contact` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `gender` varchar(4) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  `phone` varchar(11) DEFAULT NULL,
  `email` varchar(255) DEFAULT NULL,
  `qq` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=36 DEFAULT CHARSET=utf8;

/*Data for the table `contact` */

insert  into `contact`(`cid`,`name`,`gender`,`age`,`phone`,`email`,`qq`) values 
(28,'科比','男',34,'1231','1346888','ce88029a735b44d3b553a917911b13f30d6583f95051415da21b8fcdbcae8a8d4.png'),
(29,'户','男',34,'1516152','14561113@qq.com','4083a5d95fdb4442ae937bc0da1904102bafe2f833de4744878e3142d2ce488e74eacec67ede492f88c9be61c2602adfea21bcc015944f3091c270736d52c3ec5.png'),
(30,'张三','男',7848,'1551674585','1346888','9e1ae3313c5e4793ae94be0f4be69d96b59d1750411a46ff88ad3b716cf632c23.png'),
(31,'打','男',24,'1551674585','sdada13@162','53b1005dbd6a4923b782a067cdf48e0150b979f34c214911b6bf6c07035c560659cd76a4281f46eda598540a91cd50272.png');

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

pojo

package com.javacoffee.pojo;

public class Client {
    //创建Client类 和数据库中的client表对应好
    private Integer id;
    private String username;
    private String password;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

package com.javacoffee.pojo;

public class Contact {
    //创建Contact类 和数据库中的字段名对应好
    private Integer cid;
    private String name;
    private String gender;
    private Integer age;
    private String phone;
    private String email;
    private String qq;

    public Contact() {
    }

    public Integer getCid() {
        return cid;
    }

    public void setCid(Integer cid) {
        this.cid = cid;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getPhone() {
        return phone;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getQq() {
        return qq;
    }

    public void setQq(String qq) {
        this.qq = qq;
    }

    @Override
    public String toString() {
        return "Contact{" +
                "cid=" + cid +
                ", name='" + name + '\\'' +
                ", gender='" + gender + '\\'' +
                ", age=" + age +
                ", phone='" + phone + '\\'' +
                ", email='" + email + '\\'' +
                ", qq='" + qq + '\\'' +
                '}';
    }
}

dao

package com.javacoffee.dao;

import com.javacoffee.pojo.Client;

public interface ClientDao {
    Client login(String username, String password);
}

package com.javacoffee.dao;

import com.javacoffee.pojo.Contact;
import com.javacoffee.util.PageBean;

import java.util.List;

public interface ContactDao {
    //面向接口编程
    public void addContact(Contact contact);//添加联系人
    public void updateContact(Contact contact);//修改联系人
    public void deleteContact(Integer cid);//删除联系人
    public List<Contact> findAll();  //查询所有联系人
    public Contact findById(Integer cid);//根据编号查询联系人
    public PageBean findByPage(PageBean pageBean);//分页
    public void deleteAll(String[] cids);//删除全选

    Contact selectPhone(String phone);

}

dao实现类

package com.javacoffee.dao.impl;

import com.javacoffee.dao.ClientDao;
import com.javacoffee.pojo.Client;
import com.javacoffee.util.JdbcUtil;
import org.apache.commons.dbutils.handlers.BeanHandler;

import java.sql.SQLException;

public class ClientDaoImpl implements ClientDao {
    @Override
    public Client login(String username, String password) {
        //登陆的查询语句
        String sql = "select * from client where username = ? and password = ?";
        Object[] objects = {username,password};
        try {
            return  JdbcUtil.getQueryRunner().query(sql, new BeanHandler<Client>(Client.class), objects);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        throw new RuntimeException("sql语句异常");
    }

}

package com.javacoffee.dao.impl;

import com.javacoffee.dao.ContactDao;
import com.javacoffee.pojo.Contact;
import com.javacoffee.util.JdbcUtil;
import com.javacoffee.util.PageBean;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

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

public class ContactDaoImpl implements ContactDao {

    //添加联系人的方法
    @Override
    public void addContact(Contact contact) {
        //sql语句 后面加上参数
        String sql = "insert into contact(name,gender,age,phone,email,qq) values(?,?,?,?,?,?)";
        //创建一个object数组，并把需要传的参数放入数组中
        Object[] objects = {contact.getName(),contact.getGender(),contact.getAge(),contact.getPhone(),contact.getEmail(),contact.getQq()};
        try {
            //执行sql语句 我导入了dbUtil包，所以直接得到queryRunner对象执行sql语句
            JdbcUtil.getQueryRunner().update(sql,objects);
        } catch (SQLException e) {
            e.printStackTrace();
        }

    }

    @Override
    public void updateContact(Contact contact) {
        //修改的sql语句
        String sql = "update contact set name = ?,gender = ?,age=  ?,phone = ?,email = ?,qq = ? where cid = ?";
        //和增加很一样,先赋值到数组 再执行sql语句
        Object[] objects = {contact.getName(),contact.getGender(),contact.getAge(),contact.getPhone(),contact.getEmail(),contact.getQq(),contact.getCid()};
        try {
            JdbcUtil.getQueryRunner().update(sql,objects);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void deleteContact(Integer cid) {
        //删除sql语句
        String sql = "delete from contact where cid = ?";
        try {
            //传参可以直接传入sql语句和 cid形式参数
            JdbcUtil.getQueryRunner().update(sql,cid);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public List<Contact> findAll() {
        //返回值为List集合 sql语句如下
        String sql = "select * from contact";
        try {
            //也是通过dbUtil工具类来执行sql语句,因为输出的为List集合,所以第一个参数为sql语句 第二个如下
            return JdbcUtil.getQueryRunner().query(sql, new BeanListHandler<Contact>(Contact.class));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        throw new RuntimeException("列表无数据");
    }

    @Override
    public Contact findById(Integer cid) {
        //这个是通过id来进行查找
        String sql = "select * from contact where cid = ?";
        try {
            //返回值为一个对象 所以第二个参数也变成如下了,第三个参数放入cid
            return JdbcUtil.getQueryRunner().query(sql, new BeanHandler<Contact>(Contact.class), cid);
        } catch (SQLException e) {
            e.printStackTrace();
        }

        throw new RuntimeException("没有这个id");
    }
    @Override
    public PageBean findByPage(PageBean pageBean) {
        //分页 这里是通过sql语句分的 比较基础
        String sql = "select * from contact limit ?,?";
        //传入的是PageBean对象,来获取当前页号和每页的记录数
        //大家可一思考一下 select * from contact limit 0,3 是查找第一个到第三个的数据
        // select * from contact limit 3,3 是查找第四个到第六个的 以此类推
        Object[] objects = {(pageBean.getPageNum()-1)*pageBean.getPageSize(),pageBean.getPageSize()};
        try {
            //传入每页的数据
            List<Contact> query = JdbcUtil.getQueryRunner().query(sql, new BeanListHandler<Contact>(Contact.class), objects);
            pageBean.setPageData(query);

            //查找数据总数
            String sql1 = "select count(cid) from contact";
            //强转为Long类型数据
            Long query1 = (Long)JdbcUtil.getQueryRunner().query(sql1, new ScalarHandler<>());
            //将查找出来的数据再转化为int类型数据存入pageBean中
            pageBean.setTotalData(query1.intValue());
            //可以在控制台打印一下看看是不是存入
//            System.out.println(pageBean.getTotalData());

            //计算总页数  用了三目运算符
            //当 总数据数除以每页的数据数结果余数为0时候,说明总页数是总数据数除以每页的数据数结果取整
            //反之则需要加一
            Integer totalCount = pageBean.getTotalData()%pageBean.getPageSize()==0 ?
                    pageBean.getTotalData()/pageBean.getPageSize() :
                    pageBean.getTotalData()/pageBean.getPageSize() + 1;
            //然后赋值
            pageBean.setTotalCount(totalCount);
            //返回这个对象
            return pageBean;

        } catch (SQLException e) {
            e.printStackTrace();
        }
        throw new RuntimeException("无法获取对象");
    }

    @Override
    public void deleteAll(String[] cids) {
        //输入sql语句 通过cid来进行多个删除 可以看到传入的参数为cids是一个String类型的数组
        String sql = "delete from contact where cid = ?";
        //创建一个二维数组,这个数组的长度为cids中的数据数
        Object[][] objects = new Object[cids.length][];
        //通过循环来对二维数组进行赋值
        for (int i = 0; i < objects.length; i++) {
            objects[i] = new Object[]{cids[i]};
        }
        try {
            //执行sql语句
            JdbcUtil.getQueryRunner().batch(sql,objects);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public Contact selectPhone(String phone) {
        String sql = "select * from contact where phone = ?";
        try {
            Contact query = JdbcUtil.getQueryRunner().query(sql, new BeanHandler<Contact>(Contact.class), phone);
            return query;
        } catch (SQLException e) {
            e.printStackTrace();
        }
        throw new RuntimeException("查找异常");
    }


}

exception

package com.javacoffee.exception;

public class MyException extends Exception {
    public MyException(String messege){
        super(messege);
    }
}

service

package com.javacoffee.service;

import com.javacoffee.exception.MyException;
import com.javacoffee.pojo.Contact;
import com.javacoffee.util.PageBean;

import java.util.List;

public interface ContactService {
    //service层我并没写什么逻辑行为，因为比较简单，就起到了个传值的作用
    public void addContact(Contact contact) throws MyException;//添加联系人
    public void updateContact(Contact contact);//修改联系人
    public void deleteContact(Integer cid);//删除联系人
    public List<Contact> findAll();  //查询所有联系人
    public Contact findById(Integer cid);//根据编号查询联系人
    public  PageBean findByPage(PageBean pageBean);//分页
    public void deleteAll(String[] cids);//删除所选人

    Boolean selectPhone(String phone);

}

package com.javacoffee.service;

import com.javacoffee.pojo.Client;

public interface ClientService {
    //获取对象
    Client login(String username, String password);
}

service实现类

package com.javacoffee.service.impl;

import com.javacoffee.dao.ClientDao;
import com.javacoffee.dao.impl.ClientDaoImpl;
import com.javacoffee.pojo.Client;
import com.javacoffee.service.ClientService;

public class ClientServiceImpl implements ClientService {
    @Override
    public Client login(String username, String password) {
        ClientDao clientDao = new ClientDaoImpl();
        return clientDao.login(username,password);
    }
}

package com.javacoffee.service.impl;

import com.javacoffee.dao.ContactDao;
import com.javacoffee.dao.impl.ContactDaoImpl;
import com.javacoffee.exception.MyException;
import com.javacoffee.pojo.Contact;
import com.javacoffee.service.ContactService;
import com.javacoffee.util.PageBean;

import java.util.List;

public class ContactServiceImpl implements ContactService {
    //首先创建 多态父类引用指向子类对象 new出来contactDao对象
    private ContactDao contactDao = new ContactDaoImpl();
    //增加联系人的方法
    @Override
    public void addContact(Contact contact) throws MyException {
        Boolean aBoolean = selectPhone(contact.getPhone());
        if (aBoolean){
            contactDao.addContact(contact);
        }else {
            throw new MyException("手机号重复，不能使用！");
        }

    }
    //修改联系人的方法
    @Override
    public void updateContact(Contact contact) {
        contactDao.updateContact(contact);
    }
    //删除联系人的方法
    @Override
    public void deleteContact(Integer cid) {
        contactDao.deleteContact(cid);
    }
    //查找全部的方法
    @Override
    public List<Contact> findAll() {
        return contactDao.findAll();
    }
    //通过id查找的方法
    @Override
    public Contact findById(Integer cid) {
        return contactDao.findById(cid);
    }
    //分页
    @Override
    public PageBean findByPage(PageBean pageBean) {
        return contactDao.findByPage(pageBean);
    }

    @Override
    //删除所选全部
    public void deleteAll(String[] cids) {
         contactDao.deleteAll(cids);
    }

    @Override
    public Boolean selectPhone(String phone) {
        Contact contact = contactDao.selectPhone(phone);
        if (contact == null){
            return true;
        }else {
            return false;
        }
    }


}

filter过滤器

package com.javacoffee.filter;

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

@WebFilter("/*")
public class ContactFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        //字符集过滤器 过滤所有 将字符集设置成utf-8
       HttpServletRequest request = (HttpServletRequest)req;
       HttpServletResponse response = (HttpServletResponse)resp;
       request.setCharacterEncoding("utf-8");
       response.setContentType("text/html;charset=utf-8");
       chain.doFilter(request,response);
    }

    public void init(FilterConfig config) throws ServletException {

    }

}

package com.javacoffee.filter;

import com.javacoffee.pojo.Client;

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

@WebFilter("/*")
public class LoginFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        //登陆的过滤器 因为要确保先登录 所以将网址不是登录的重定向到登录界面
        HttpServletRequest request = (HttpServletRequest)req;
        HttpServletResponse response = (HttpServletResponse)resp;
        //获取后缀
        String requestURI = request.getRequestURI();
        requestURI = requestURI.substring(requestURI.lastIndexOf("/"));
        //判断如果输入的网址后缀是这两个 则放行
         if ("/loginServlet".equals(requestURI)|| "/login.jsp".equals(requestURI)){
             chain.doFilter(request,response);
         }else {
             //如果不是的话 因为我们在登录的时候创建了session 如果session为空
             //那么一定是没有登录的 所以不放行重定向到登陆界面
             HttpSession session = request.getSession(false);
             if (session == null){
                 response.sendRedirect(request.getContextPath()+"/loginServlet");
             }else {
                 //如果存在session 对象 不过有可能session对象里是在别的地方创建好的
                 //所以我们要判断session里是否存储了我们登陆时存进去的client对象
                 //如果没有的话那还是没登陆 就重定向到登陆界面
                 Client client = (Client)session.getAttribute("client");
                 if (client == null){
                     response.sendRedirect(request.getContextPath()+"/loginServlet");
                 }else {
                     //反之 就是登录过的 就可以放行
                     chain.doFilter(request,response);
                 }
             }
         }

    }

    public void init(FilterConfig config) throws ServletException {

    }

}

util工具类

package com.javacoffee.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.apache.commons.dbutils.QueryRunner;

import javax.sql.DataSource;
import java.io.InputStream;
import java.util.Properties;

//使用DBUtils的工具类
public class JdbcUtil {

    //声明DataSource对象
    private static DataSource dataSource;

    //静态代码块
    static {

        try {
            //读取db.properties文件
            InputStream resourceAsStream = JdbcUtil.class.getResourceAsStream("/druid.properties");
            //创建Properties对象
            Properties properties = new Properties();
            //加载流对象
            properties.load(resourceAsStream);
            //创建数据源对象
            dataSource = DruidDataSourceFactory.createDataSource(properties);

        } catch (Exception e) {
            e.printStackTrace();
        }

    }


    //获取DButils中核心类对象QueryRunner对象
    public static QueryRunner getQueryRunner(){
        return new QueryRunner(dataSource);//此时已经连接上数据库了
    }

}

package com.javacoffee.util;

public class PageBean {
    //这是分页的工具类,一共需要获得五个属性
    private Integer pageNum;//当前页码号 通过前端获取
    private Integer pageSize;//一页的记录数 自己设置的
    private Object pageData;//一页的数据 可以看到返回值是对象
    private Integer totalCount;//总页数 需要二次计算
    private Integer totalData;//数据的总记录数 用来计算总页数用的


    public Integer getPageNum() {
        return pageNum;
    }

    public void setPageNum(Integer pageNum) {
        this.pageNum = pageNum;
    }

    public Integer getPageSize() {
        return pageSize;
    }

    public void setPageSize(Integer pageSize) {
        this.pageSize = pageSize;
    }

    public Object getPageData() {
        return pageData;
    }

    public void setPageData(Object pageData) {
        this.pageData = pageData;
    }

    public Integer getTotalCount() {
        return totalCount;
    }

    public void setTotalCount(Integer totalCount) {
        this.totalCount = totalCount;
    }

    public Integer getTotalData() {
        return totalData;
    }

    public void setTotalData(Integer totalData) {
        this.totalData = totalData;
    }

    @Override
    public String toString() {
        return "PageBean{" +
                "pageNum=" + pageNum +
                ", pageSize=" + pageSize +
                ", pageData=" + pageData +
                ", totalCount=" + totalCount +
                ", totalData=" + totalData +
                '}';
    }
}

druid.properties数据库连接池配置文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/contact_sys?useSSL=false
#我是使用的mysql 所以端口号为3306 数据库账户密码一定要改成自己的哈
username=root
password=1234

initialSize=5
maxActive=20
maxWait=2000

web层

package com.javacoffee.web;

import com.javacoffee.exception.MyException;
import com.javacoffee.pojo.Contact;
import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.File;
import java.io.IOException;
import java.util.UUID;
//注意这两个注解千万不能省略
@WebServlet("/addContactServlet")//这个是servlet的注解,可以访问的到
@MultipartConfig//这个是代表上传文件的注解
public class AddContactServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //这是增加联系人的servlet 首先设置字符集
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        //新建一个contact对象 用来存储数据库中获取的数据
        Contact contact = new Contact();
        //通过前端所对应的键名来获取相应的值
        String name = request.getParameter("name");
        String gender = request.getParameter("gender");
        String age = request.getParameter("age");
        String phone = request.getParameter("phone");
        String email = request.getParameter("email");
        //这里是上传文件 获取上传的对象
        Part qq = request.getPart("qq");
        //获取所上传文件的名字
        String qqName = qq.getSubmittedFileName();
        //为了避免上传的文件后,文件重复 每次上传文件都会通过UUID 工具类获取一个随机的字符串作为前缀名
        String replace = UUID.randomUUID().toString().replace("-", "");
       //我是把文件上传到另一个tomcat服务器里 所以这里把他的路径给出来了
        String uploadPath = "D:\\\\apache-tomcat-8.5.31\\\\webapps\\\\imgs";
       //通过路径创建一个新的文件对象
        File file = new File(uploadPath);
        //如果没有这个文件的话,就创建
        if (!file.exists()){
            file.mkdirs();
        }
        //最后组成文件的名字
        String uploadFileName = replace+qqName;
        //然后给他上传一下,参数为(路径+文件名) 注意这两个之间要加斜杠
        qq.write(uploadPath+"/"+uploadFileName);
        //接着赋值给对象
        contact.setName(name);
        contact.setAge(Integer.parseInt(age));
        contact.setEmail(email);
        contact.setGender(gender);
        contact.setPhone(phone);
        contact.setQq(uploadFileName);
        //接着调用addContact方法
        ContactService contactService = new ContactServiceImpl();
        try {
            contactService.addContact(contact);
        } catch (MyException e) {
            request.setAttribute("msg",e.getMessage());
            request.getRequestDispatcher("addContact.jsp").forward(request,response);
        }

        //因为不需要传值 重定向到首页面
        response.sendRedirect(request.getContextPath()+"/pageServlet");
    }
}

package com.javacoffee.web;

import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Arrays;

@WebServlet("/contactDeleteAllServlet")
public class ContactDeleteAllServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");

        String[] cids = request.getParameterValues("cids");
        if (cids != null) {
            ContactService contactService = new ContactServiceImpl();
            contactService.deleteAll(cids);
            response.sendRedirect(request.getContextPath()+"/pageServlet");
        }else {
            response.sendRedirect(request.getContextPath() + "/pageServlet");
        }
    }
}

package com.javacoffee.web;

import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;
import com.javacoffee.util.PageBean;

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

@WebServlet("/contactDeleteServlet")
public class ContactDeleteServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");

        ContactService contactService = new ContactServiceImpl();
        String cid = request.getParameter("cid");
        contactService.deleteContact(Integer.parseInt(cid));

        response.sendRedirect(request.getContextPath()+"/pageServlet");
    }
}

package com.javacoffee.web;

import com.javacoffee.pojo.Contact;
import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet("/contactFindAllServlet")
public class ContactFindAllServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        ContactService contactService = new ContactServiceImpl();
        List<Contact> contactList = contactService.findAll();
        request.setAttribute("contactList",contactList);
        request.getRequestDispatcher("findAll.jsp").forward(request,response);
    }
}

package com.javacoffee.web;

import com.javacoffee.pojo.Contact;
import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;

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

@WebServlet("/findByIdServlet")
public class FindByIdServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        ContactService contactService = new ContactServiceImpl();
        String cid = request.getParameter("cid");
        Contact contact = contactService.findById(Integer.parseInt(cid));
        request.setAttribute("contact",contact);
        request.getRequestDispatcher("update.jsp").forward(request,response);
    }

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

package com.javacoffee.web;

import com.javacoffee.pojo.Client;
import com.javacoffee.pojo.Contact;
import com.javacoffee.service.ClientService;
import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ClientServiceImpl;
import com.javacoffee.service.impl.ContactServiceImpl;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ClientService clientService = new ClientServiceImpl();
        //获取前端输入框的数据
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //调用login方法 并返回client对象
        Client client = clientService.login(username,password);
        //如果client不为空的话也就是有这个账号密码  就 将client存入session 转发到主界面 也就是登录成功跳转
        if (client != null){
            HttpSession session = request.getSession();
            session.setAttribute("client",client);
            request.getRequestDispatcher("pageServlet").forward(request,response);
        }else {
            //如果为空就代表没有这个代码 就重定向到登陆界面
            response.sendRedirect(request.getContextPath()+"/login.jsp");
        }
    }
}

package com.javacoffee.web;

import com.javacoffee.pojo.Client;
import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;
import com.javacoffee.util.PageBean;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;

@WebServlet("/pageServlet")
public class PageServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");

        String pageNum = request.getParameter("pageNum");
        if (pageNum==null){
            pageNum="1";
        }
        Integer pageSize = 4;
        PageBean pageBean1 = new PageBean();
        pageBean1.setPageNum(Integer.parseInt(pageNum));
        pageBean1.setPageSize(pageSize);
        ContactService contactService = new ContactServiceImpl();
        PageBean pageBean = contactService.findByPage(pageBean1);
        request.setAttribute("pageBean",pageBean);
        HttpSession session = request.getSession(false);
        Client client = (Client)session.getAttribute("client");
        request.setAttribute("client",client);
        request.getRequestDispatcher("findAll.jsp").forward(request,response);
    }
}

package com.javacoffee.web;


import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;

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

@WebServlet("/selectPhoneServlet")
public class SelectPhoneServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");

        String phone = request.getParameter("phone");
        ContactService contactService = new ContactServiceImpl();
        Boolean statement = contactService.selectPhone(phone);
        if (statement){
            response.getWriter().write("noExist");
        }else {
            response.getWriter().write("exist");
        }
    }
}

package com.javacoffee.web;

import com.javacoffee.pojo.Contact;
import com.javacoffee.service.ContactService;
import com.javacoffee.service.impl.ContactServiceImpl;
import com.javacoffee.util.PageBean;

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.File;
import java.io.IOException;
import java.util.UUID;

@WebServlet("/updateServlet")
@MultipartConfig
public class UpdateServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        String cid = request.getParameter("cid");
        String name = request.getParameter("name");
        String gender = request.getParameter("gender");
        String age = request.getParameter("age");
        String phone = request.getParameter("phone");
        String email = request.getParameter("email");
        Part qq = request.getPart("qq");

        String updateFilePath = "D:\\\\apache-tomcat-8.5.31\\\\webapps\\\\imgs";
        File file = new File(updateFilePath);
        if (file.exists()) {
            file.mkdirs();
        }
        String submittedFileName = qq.getSubmittedFileName();

        String updateFileName = UUID.randomUUID().toString().replace("-", "") + submittedFileName;
        qq.write(updateFilePath + "\\\\" + updateFileName);

        ContactService contactService = new ContactServiceImpl();
        Contact contact = new Contact();
        contact.setCid(Integer.parseInt(cid));
        contact.setName(name);
        contact.setAge(Integer.parseInt(age));
        contact.setEmail(email);
        contact.setGender(gender);
        contact.setPhone(phone);
        contact.setQq(updateFileName);
        contactService.updateContact(contact);
        response.sendRedirect(request.getContextPath() + "/pageServlet");
    }

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

前端代码

<%--
  Created by IntelliJ IDEA.
  User: 86156
  Date: 2021/9/30
  Time: 15:10
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录界面</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous">

</head>
<body style="background-color:burlywood">
<center><h1>用户登陆页面</h1></center>
<div style="background-color: beige;width: 500px;height: 300px;position: absolute;top: 100px;left:520px;border-radius: 10px">
<form class="form-horizontal" action="loginServlet" method="post">
    <div style="position: absolute;top: 50px;left: 100px">
    <div class="form-group">
        <label for="inputEmail3" class="col-sm-2 control-label">UserName：</label>
        <div class="col-sm-10" style="position: absolute;left: 100px;width: 200px">
            <input type="text" name="username" class="form-control" id="inputEmail3" placeholder="Email" >
        </div>
    </div>
    <div class="form-group">
        <label for="inputPassword3" class="col-sm-2 control-label">PassWord：</label>
        <div class="col-sm-10" style="position: absolute;left: 100px;width: 200px">
            <input type="password" name="password" class="form-control" id="inputPassword3" placeholder="Password" >
        </div>
    </div>
        <br>
    <div class="form-group" style="position: absolute;left: 170px">
        <div class="col-sm-offset-2 col-sm-10">
            <button type="submit" class="btn btn-default" style="width: 90px">登录</button>
        </div>
    </div>
    </div>
</form>
</div>
</body>
</html>

<%--
  Created by IntelliJ IDEA.
  User: 86156
  Date: 2021/9/28
  Time: 11:14
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
    <style>
       table{
           text-align: center;
           vertical-align: middle;
       }

    </style>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous">
</head>
<body bgcolor="#6495ed">
<font color="#deb887" size="6" style="background-color: beige">欢迎：${client.username}&nbsp;登录！</font>
<form action="contactDeleteAllServlet" method="post" >
<table class="table table-hover table-bordered" style="width: 80%" align="center">
    <tr class="success" style="font-weight: bold">
        <td><input type="checkbox"  id="cids" onclick="selectAll()">全选</td>
        <td>编号</td>
        <td>姓名</td>
        <td>性别</td>
        <td>年龄</td>
        <td>电话</td>
        <td>邮箱</td>
        <td>QQ</td>
        <td>操作</td>
    </tr>
<%--    <c:forEach items="${contactList}" var="contactList" varStatus="c">--%>
    <c:forEach items="${pageBean.pageData}" var="contactList" varStatus="c">
    <tr class="active" style="vertical-align: center">
        <td align="center"><input type="checkbox" class="checkbox" name="cids" value="${contactList.cid}"></td>
        <td>${c.count}</td>
        <td>${contactList.name}</td>
        <td>${contactList.gender}</td>
        <td>${contactList.age}</td>
        <td>${contactList.phone}</td>
        <td>${contactList.email}</td>
<%--        //图片显示的路径 我的是自己又开了一个tomcat端口号为9999--%>
        <td><img src="http://10.8.159.4:9999/imgs/${contactList.qq}" width="60" height="60"></td>
        <td><a href="${pageContext.request.contextPath}/findByIdServlet?cid=${contactList.cid}">修改</a>&nbsp;

            <a href="${pageContext.request.contextPath}/contactDeleteServlet?cid=${contactList.cid}">删除</a>

            <c:if test="${pageBean.pageData==null}">
                ${pageBean.pageNum=pageBean.pageNum-1}
            </c:if>
        </td>
    </tr>
    </c:forEach>
    <tr class="warning" >
        <td colspan="9" align="center"><a href="addContact.jsp">[添加联系人]</a></td>
    </tr>

    <tr class="warning" >
        <td colspan="9" align="center"><input type="submit" value="全部删除"></td>
    </tr>


    <tr class="warning" >
        <td colspan="9" align="center">
            &nbsp;&nbsp;第${pageBean.pageNum}页&nbsp;&nbsp;${pageBean.pageNum}/${pageBean.totalCount}页&nbsp;&nbsp;
            <a href="${pageContext.request.contextPath}/pageServlet?pageNum=1">首页</a>

            <c:if test="${pageBean.pageNum == 1}">
                <a>上一页</a>
            </c:if>

            <c:if test="${pageBean.pageNum > 1}">
                <a href="${pageContext.request.contextPath}/pageServlet?pageNum=${pageBean.pageNum-1}">上一页</a>
            </c:if>

            <c:if test="${pageBean.pageNum == pageBean.totalCount}">
                <a>下一页</a>
            </c:if>

            <c:if test="${pageBean.pageNum < pageBean.totalCount}">
                <a href="${pageContext.request.contextPath}/pageServlet?pageNum=${pageBean.pageNum+1}">下一页</a>
            </c:if>

            <a href="${pageContext.request.contextPath}/pageServlet?pageNum=${pageBean.totalCount}">尾页</a>
        </td>
    </tr>
</table>
</form>
</body>
<script type="application/javascript">
    function selectAll() {
        var cids = document.getElementById("cids");
        var elementsByClassName = document.getElementsByClassName("checkbox");
        for (var i = 0; i < elementsByClassName.length; i++) {
            elementsByClassName[i].checked = cids.checked;
        }
    }
</script>
</html>

<%--
  Created by IntelliJ IDEA.
  User: 86156
  Date: 2021/9/28
  Time: 15:08
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>添加联系人</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous">
    <script src="https://ajax.aspnetcdn.com/ajax/jquery/jquery-3.5.1.min.js"></script>

</head>

<body>
<center><h3>添加联系人</h3></center>

<form action="addContactServlet" method="post" enctype="multipart/form-data">
    <table align="center" border="1" width="300px" class="table table-bordered table-hover">
        <tr class="warning"><td colspan="2"><font color="red" size="5">${msg}</font></td></tr>
        <tr class="success">
            <th>姓名</th>
            <td><input type="text" name="name"/></td>
        </tr>
        <tr class="warning">
            <th >性别</th>
            <td>
                <input type="radio" name="gender" value="男" checked="checked" />男
                <input type="radio" name="gender" value="女"/>女
            </td>
        </tr>
        <tr class="active">
            <th>年龄</th>
            <td><input type="text" name="age"/></td>
        </tr>
        <tr class="danger">
            <th>电话</th>
            <td><input type="text" name="phone" id="phone" onfocus="waring()" onblur="findPhone()"/>
            <span id="phoneSpan"></span></td>
        </tr>
        <tr class="info">
            <th>邮箱</th>
            <td><input type="text" name="email"/></td>
        </tr>
        <tr>
            <th>QQ</th>
            <td><input type="file" name="qq"/></td>
        </tr>
        <tr>
            <td colspan="2" align="center">
                <input type="submit" value="保存"/>&nbsp;
                <input type="reset" value="重置"/></td>
        </tr>
    </table>
</form>
</body>
<script type="application/javascript">
    function waring() {
        var elementById = document.getElementById("phoneSpan");
        elementById.innerHTML="手机号为11位".fontcolor("red");
    }
    function findPhone() {
        var elementById = document.getElementById("phoneSpan");
        var selectPhone = document.getElementById("phone").value;

        $.get("selectPhoneServlet",{phone:selectPhone},
        function (backdata) {
            if (backdata=="exist"){
                elementById.innerHTML="手机号已存在".fontcolor("red");
            }else if (backdata=="noExist") {
                elementById.innerHTML="手机号可以使用".fontcolor("green");
            }
        },"text")
    }
</script>
</html>

<%--
  Created by IntelliJ IDEA.
  User: 86156
  Date: 2021/9/28
  Time: 19:12
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>修改联系人</title>
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css" integrity="sha384-HSMxcRTRxnN+Bdg0JdbxYKrThecOKuH5zCYotlSAcp1+c8xmyTe9GYg1l9a69psu" crossorigin="anonymous">
</head>

<body>
<center><h3>修改联系人</h3></center>
<form action="updateServlet" method="post" enctype="multipart/form-data">
    <input type="hidden" name="cid" value="${contact.cid}">
    <table align="center" border="1" width="300px" class="table table-hover table-bordered">
        <tr class="active">
            <th>姓名</th>
            <td><input type="text" name="name" value="${contact.name}"/></td>
        </tr>
        <tr class="success">
            <th>性别</th>
            <c:if test="${contact.gender=='男'}">
            <td>
                <input type="radio" name="gender" value="男" checked="checked"/>男
                <input type="radio" name="gender" value="女"/>女
            </td>
            </c:if>
            <c:if test="${contact.gender=='女'}">
                <td>
                    <input type="radio" name="gender" value="男"/>男
                    <input type="radio" name="gender" value="女" checked="checked"/>女
                </td>
            </c:if>
        </tr>
        <tr class="warning">
            <th>年龄</th>
            <td><input type="text" name="age" value="${contact.age}"/></td>
        </tr>
        <tr class="info">
            <th>电话</th>
            <td><input type="text" name="phone" value="${contact.phone}"/></td>
        </tr>
        <tr class="success">
            <th>邮箱</th>
            <td><input type="text" name="email" value="${contact.email}"/></td>
        </tr>
        <tr class="danger">
            <th>QQ</th>
            <td><img src="http://localhost:9999/imgs/${contact.qq}" width="60" height="60"><input type="file" name="qq"/></td>
        </tr>
        <tr>
            <td colspan="2" align="center">
                <input type="submit" value="保存"/>&nbsp;
                <input type="reset" value="重置"/></td>
        </tr>
    </table>
</form>
</body>
</html>