8_文件上传与下载

时间：2021-04-19 01:41:11 阅读：16 评论：0 收藏：0 [点我收藏+]

一. 引言
- 1.1 场景
二. 文件上传
三. 文件下载
四. EMS综合项目
五. Web开发总结
- 5.1 开发流程

一. 引言

1.1 场景

在项目中, 文件的上传和下载是常见的功能, 很多程序或者软件中都经常使用到文件的上传和下载
邮箱中有附件的上传和下载
OA办公系统中有附件材料的上传

二. 文件上传

2.1 概念

当用户在前端页面点击文件上传后, 用户上传的文件数据提交给服务器端, 实现保存

2.2 文件上传实现步骤

2.2.1 提交方式

提供form表单, method必须是post, 因为post请求无数据限制

<form method="post">
    
</form>

2.2.2 提交数据格式

表单的enctype属性值必须为multipart/form-data
以多段的形式进行拼接提交, 以二进制流的方式来处理表单数据, 会把指定的文件内容封装进请求参数中

<form enctype="multipart/form-data" method="post">
    
</form>

2.2.3 提供组件

提供file表单组件, 提供给用户上传文件

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>文件上传页面</title>
</head>
<body>
    <form action="${pageContext.request.contextPath}/upload" enctype="multipart/form-data" method="post">
        <p>用户名:
            <input type="text" name="username">
        </p>
        <p>密码:&nbsp;&nbsp;&nbsp;
            <input type="file" name="file1">
        </p>
        <p>
            <input type="submit" value="上传">
        </p>
    </form>
</body>
</html>

2.2.4 Controller编写

在Servlet 3.0 及其以上版本的容器中进行服务器端文件上传的编程, 是围绕着注解类型MultipartConfig 和 javax.servlet.http.Part 接口进行的, 处理已上传文件的Servlet必须以@MultipartConfig进行注解

package com.dz.servlet;

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;

@WebServlet(name = "uploadController",value = "/upload")
@MultipartConfig(maxFileSize = 1024*1024*100,maxRequestSize = 1024*1024*200)
public class uploadController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //实现文件上传

        //1. 设置乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        //2. 获取请求的数据
        String username = request.getParameter("username");
        Part part = request.getPart("file1");

        //3. 获取上传文件的路径(将上传的文件存到此路径下)  真实路径
        String uploadPath = request.getServletContext().getRealPath("/WEB-INF/upload");
        File file = new File(uploadPath);
        if (!file.exists()) {
            file.mkdirs();//新建文件夹
        }

        //4. 文件上传
        part.write(uploadPath+"\\"+part.getSubmittedFileName());

        //5. 响应客户端 上传成功
        response.getWriter().println(part.getSubmittedFileName()+"上传成功!");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

2.3 文件上传细节注意

上述代码虽然可以成功将文件上传到服务器的指定目录当中, 但是文件上传功能有许多需要注意的小细节问题

2.3.1 安全问题

为保证服务器安全, 上传的文件应该放在外界无法直接访问的目录下, 比如放于WEB-INF目录下

String uploadPath = request.getServletContext().getRealPath("/WEB-INF/upload");

2.3.2 文件覆盖

当上传重名的文件时, 为防止文件覆盖的现象发生, 要为上传文件产生一个唯一的文件名

package com.dz.utils;

import java.util.UUID;

public class UploadUtils {
    //使用UUID生成唯一标识码, 并拼接上图片的名称
    public static String newFileName(String filename) {
        return UUID.randomUUID().toString().replaceAll("-","") + "_" + filename;
    }
}

//4. 文件上传
// 生成唯一文件名
//String oldName = part.getSubmittedFileName();
//String newName = UploadUtils.newFileName(oldName);
//part.write(uploadPath+"\\"+newName);

2.3.3 散列存储

为防止一个目录下面出现太多文件, 要使用hash算法生成二级, 三级目录, 散列存储上传的文件

public class UploadUtils {
    //使用UUID生成唯一标识码, 并拼接上图片的名称
    public static String newFileName(String filename) {
        return UUID.randomUUID().toString().replaceAll("-","") + "_" + filename;
    }

    //生成二三级目录,进行散列存储
    public static String newFilePath(String basePath, String fileName) {
        int hashcode = fileName.hashCode();
        int path1 = hashcode & 15;//二级目录  与运算 0~15
        int path2 = (hashcode>>4) & 15;//三级目录   与运算 0~15
        String newPath = basePath + "\\" + path1 + "\\" + path2;//一二三级目录拼接在一起
        File file = new File(newPath);//创建文件夹对象
        if (!file.exists()) {//不存在则创建
            file.mkdirs();
        }
        return newPath;//返回新路径
    }
}
//4. 文件上传
// 生成唯一文件名
//String oldName = part.getSubmittedFileName();
//String newName = UploadUtils.newFileName(oldName);
//生成二级三级目录, 实现散列存储
//String newPath = UploadUtils.newFilePath(uploadPath, oldName);
//part.write(newPath+"\\"+newName);

技术分享图片

2.3.4 文件类型限制

要限制上传文件的类型, 在收到上传文件名时, 判断后缀名是否合法

//创建一个集合存放允许上传的文件类型(后缀名)
//判断集合中是否包含上传文件的后缀名
List<String> nameList = new ArrayList<>();
nameList.add(".png");
nameList.add(".jpg");
nameList.add(".jpeg");

String extName = oldName.substring(oldName.lastIndexOf("."));//从每个上传文件名中的最后出现点的位置开始截取, 也就是截取 后缀名(包括.)
if (!nameList.contains(extName)) {
    response.getWriter().println(oldName + "的文件类型不支持上传!");
    return;
}

2.4 多文件上传

package com.dz.servlet;

import com.dz.utils.UploadUtils;

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.ArrayList;
import java.util.Collection;
import java.util.List;

/**
 * @belongsProject: FileUpload
 * @belongsPackage: ${PACKAGE_NAME}
 * @author: zheng
 * @description: ${Description}
 * @createTime: 2021-04-17 18:24
 * @since v1.0.0
 */

@WebServlet(name = "MoreUploadController",value = "/moreUpload")
@MultipartConfig(maxFileSize = 1024*1024*100, maxRequestSize = 1024*1024*200)
public class MoreUploadController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //实现多文件上传
        //1. 设置乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        //2. 获取上传文件的保存路径, 将上传的文件存放于WEB-INF目录下, 不允许外界直接访问, 保证上传文件的安全
        String basePath = request.getServletContext().getRealPath("/WEB-INF/upload");
        File file = new File(basePath);
        if (!file.exists()) {
            file.mkdirs();//WEB-INF下新建upload文件夹
        }
        //3. 获得表单提交的所有数据,放在集合里
        Collection<Part> parts = request.getParts();

        //4. 遍历集合
        if (parts != null) {
            for (Part part : parts) {
                //4.1 获取上传文件的文件名
                String fileName = part.getSubmittedFileName();
                if (fileName != null) {//文件名不为空后我们认为是 文件数据
                    //二次判断(看文件名是否为空字符串),避免用户传入空数据
                    if (fileName.trim().equals("")) {
                        continue;
                    }
                    //4.1.1 调用上传工具类中的newFileName方法生成新的唯一文件名(使用UUID生成唯一标识码)
                    String newName = UploadUtils.newFileName(fileName);
                    //4.1.2 创建集合, 里面存放文件的后缀名,如果所上传文件的后缀名不在此集合内, 则不允许上传
                    List<String> fileNameList = new ArrayList<>();
                    fileNameList.add(".jpg");
                    fileNameList.add(".png");
                    fileNameList.add(".jpeg");
                    //截取文件后缀名(包括.)  从每个上传文件名中的最后出现点的位置开始截取
                    String extName = fileName.substring(fileName.lastIndexOf("."));
                    if (!fileNameList.contains(extName)) {
                        response.getWriter().println(fileName + "的文件类型不支持上传!");
                        return;
                    }
                    //4.1.3 获取分散后的路径,调用上传工具类中的newFilePath方法生成二级三级目录, 实现散列存储(文件名hashcode的与运算)
                    String newPath = UploadUtils.newFilePath(basePath,fileName);
                    //4.1.4 把新文件路径和新文件名进行拼接, 然后写入文件数据
                    part.write(newPath + "\\" + newName);
                    //4.1.5 响应给客户端结果
                    response.getWriter().println(part.getSubmittedFileName()+"上传成功!");
                }else{//没有获取到文件名则证明是 普通表单
                    //获取普通表单数据
                    String username = request.getParameter("username");
                    System.out.println(username);
                }
            }
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

三. 文件下载

3.1 概念

我们要将Web应用系统中的文件资源提供给用户进行下载, 首先我们要有一个页面列出上传文件目录下的所有文件, 当用户点击文件下载超链接时就进行下载操作

3.2 获取文件列表

3.2.1 DownLoadUtils

package com.dz.utils;

import java.io.File;
import java.util.HashMap;

public class DownLoadUtils {
    public static void getFileList(File file, HashMap<String,String> fileMap) {
        //获取当前文件对象下的所有内容(文件,文件夹)
        File[] files = file.listFiles();
        //如果数组不为空, 证明有文件或文件夹
        if (files != null) {
            //每次拿到文件对象(文件,文件夹)
            for (File file1 : files) {
                //如果是文件夹
                if (file1.isDirectory()) {
                    //则递归调用getFileList方法
                    getFileList(file1,fileMap);
                }else {
                    //获得文件名称
                    String fileName = file1.getName();
                    //获取第一个_的下标
                    int index = fileName.indexOf("_");
                    //获取源文件名称(去掉UUID_后的文件名)
                    String realName = fileName.substring(index + 1);
                    //UUID 键   源文件名 值
                    fileMap.put(fileName,realName);
                }
            }
        }
    }
}

3.2.2 FileListController

package com.dz.servlet;

import com.dz.utils.DownLoadUtils;

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.File;
import java.io.IOException;
import java.util.HashMap;

@WebServlet(name = "FileListController",value = "/fileList")
public class FileListController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 解决乱码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        //2. 获取文件列表
        //集合,map  key=UUID  value=源文件名称
        HashMap<String,String> fileMap = new HashMap<>();
        String basePath = request.getServletContext().getRealPath("/WEB-INF/upload");
        DownLoadUtils.getFileList(new File(basePath),fileMap);

        //3. 转发 将fileMap存储到request作用域中并转发到fileList.jsp页面
        request.setAttribute("fileMap",fileMap);
        request.getRequestDispatcher("/fileList.jsp").forward(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

3.3 下载

3.3.1 fileList.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>文件下载页面</title>
</head>
<body>
    <table>
        <tr>
            <th>文件名</th>
            <th>操作</th>
        </tr>
        <c:forEach var="entry" items="${fileMap}" >
            <tr>
                <td>${entry.value}</td>
                <td><a href="${pageContext.request.contextPath}/downLoad?filename=${entry.key}">下载</a></td>
            </tr>
        </c:forEach>

    </table>
</body>
</html>

3.3.2 DownLoadController

package com.dz.servlet;

import com.dz.utils.UploadUtils;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;

@WebServlet(name = "DownLoadController",value = "/downLoad")
public class DownLoadController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");//处理用户名的乱码
        response.setContentType("text/html;charset=UTF-8");
        String basePath = request.getServletContext().getRealPath("/WEB-INF/upload");
        //1. 获取UUID 文件名
        String uuidFilename = request.getParameter("filename");
        //通过_拆分 UUID和源文件名称,_后是源文件名称
        String filename = uuidFilename.split("_")[1];
        //通过上传工具类, 使用源文件名称获得散列存储的路径, 就是要下载的路径
        String downLoadPath = UploadUtils.newFilePath(basePath, filename);
        //设置响应头, 告诉浏览器响应的文件类型和如何处理该文件, 附件下载
        response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(filename,"UTF-8"));
        
        //2. 使用流读取
        FileInputStream fis = new FileInputStream(downLoadPath + "\\" + uuidFilename);
        ServletOutputStream sos = response.getOutputStream();
        byte[] buffer = new byte[1024*1024*100];
        int len = 0;
        while ((len=fis.read(buffer)) != -1) {
            sos.write(buffer,0,len);
        }
        
        //3. 关闭流
        sos.close();
        fis.close();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

四. EMS综合项目

4.1 项目需求

将提供好的HTML页面, 修改为JSP
实现管理员登陆功能, 并应用权限验证
对员工实现增删改查
查询员工使用分页查询, 并提供首页, 尾页, 上一页, 下一页

4.2 项目搭建

4.2.1 项目目录搭建

com.dz.ems.utils 工具包
com.dz.ems.entity 实例类
com.dz.ems..dao 数据访问接口
com.dz.ems.dao.impl 数据访问实现类
com.dz.ems.service 业务逻辑接口
com.dz.ems..service.impl 业务逻辑实现类
com.dz.ems.controller 控制器
com.dz.ems.filter 过滤器

4.2.2 项目资源引入

创建EMS项目, 在web的WEB-IF下创建lib目录并导入相关jar文件
- commons-dbutils-1.7.jar
- druid-1.1.5.jar
- jstl.jar
- mysql-connector-java-5.1.25-bin.jar
- standard.jar
- ValidateCode.jar

4.2.3 数据库创建

#创建ems数据库
CREATE DATABASE ems;
#使用ems数据库
USE ems;
#创建员工表
CREATE TABLE emp(
	id INT PRIMARY KEY AUTO_INCREMENT,
	NAME VARCHAR(20) NOT NULL,
	salary DOUBLE NOT NULL,
	age INT NOT NULL
)CHARSET=utf8;
#创建管理员表
CREATE TABLE empManager(
	username VARCHAR(20) NOT NULL,
	PASSWORD VARCHAR(20) NOT NULL
)CHARSET=utf8;
#请自行插入多条数据
INSERT INTO emp(NAME,salary,age) VALUES(‘DZ1‘,1000,18);
INSERT INTO empManager(username,PASSWORD) VALUES(‘admin‘,‘admin‘);

4.3.4 database.properties

#<!-- 连接设置 -->
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/ems?useUnicode=true&characterEncoding=UTF-8
username=root
password=root
#<!-- 初始化连接 -->
initialSize=10
#<!-- 最大连接数量 -->
maxActive=50
#<!-- 最小空闲连接 -->
minIdle=5
#<!-- 超时等待时间以毫秒为单位 60000毫秒/1000等于60秒 -->
maxWait=5000

4.3 项目开发

4.3.1 Dbutils工具类

public class DbUtils {
    private static DruidDataSource ds;
    private static final ThreadLocal<Connection> THREAD_LOCAL = new ThreadLocal<>();

    static {
        Properties properties = new Properties();
        InputStream inputStream = DbUtils.class.getResourceAsStream("/database.properties");
        try {
            properties.load(inputStream);
            ds = (DruidDataSource) DruidDataSourceFactory.createDataSource(properties);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static Connection getConnection(){
        Connection conn = THREAD_LOCAL.get();
        try {
            if (conn == null) {
                conn = ds.getConnection();
                THREAD_LOCAL.set(conn);
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return conn;
    }

    public static void begin() {
        Connection conn = null;
        try {
            conn = getConnection();
            conn.setAutoCommit(false);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

    public static void commit() {
        Connection conn = null;
        try {
            conn = getConnection();
            conn.commit();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
            closeAll(conn,null,null);
        }
    }

    public static void rollback() {
        Connection conn = null;
        try {
            conn = getConnection();
            conn.rollback();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
            closeAll(conn,null,null);
        }
    }

    public static void closeAll(Connection conn, Statement statement, ResultSet resultSet) {
        try {
            if (resultSet != null) {
                resultSet.close();
            }
            if (statement != null) {
                statement.close();
            }
            if (conn != null) {
                conn.close();
                THREAD_LOCAL.remove();
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }
}

4.3.2 EmpManager实体类

public class EmpManager {
    private String username;
    private String password;


    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;
    }

    public EmpManager(String username, String password) {
        this.username = username;
        this.password = password;
    }

    public EmpManager() {
    }
}

4.3.3 Emp实体类

public class Emp {
    private int id;
    private String name;
    private double salary;
    private int age;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public int getAge() {
        return age;
    }

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

    public Emp(int id, String name, double salary, int age) {
        this.id = id;
        this.name = name;
        this.salary = salary;
        this.age = age;
    }

    public Emp(String name, double salary, int age) {
        this.name = name;
        this.salary = salary;
        this.age = age;
    }

    public Emp() {
    }
}

4.3.4 Page实体类

public class Page {
    private Integer pageIndex;//页码
    private Integer pageSize;//单页数据量
    private Integer totalCounts;//数据总量
    private Integer totalPages;//总页数
    private Integer beginRow;//起始行

    public Page(Integer pageIndex, Integer pageSize) {
        this.pageIndex = pageIndex;
        this.pageSize = pageSize;
        this.setBeginRow((pageIndex-1) * pageSize);
    }

    public Page(Integer pageIndex) {
        this(pageIndex,5);
    }

    public Integer getPageIndex() {
        return pageIndex;
    }

    public void setPageIndex(Integer pageIndex) {
        this.pageIndex = pageIndex;
    }

    public Integer getPageSize() {
        return pageSize;
    }

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

    public Integer getTotalCounts() {
        return totalCounts;
    }

    public void setTotalCounts(Integer totalCounts) {
        this.totalCounts = totalCounts;
        this.setTotalPages(totalCounts % pageSize == 0?totalCounts/pageSize:totalCounts/pageSize+1);
    }

    public Integer getTotalPages() {
        return totalPages;
    }

    public void setTotalPages(Integer totalPages) {
        this.totalPages = totalPages;
    }

    public Integer getBeginRow() {
        return beginRow;
    }

    public void setBeginRow(Integer beginRow) {
        this.beginRow = beginRow;
    }
}

4.3.5 EmpManagerDao

public interface EmpManagerDao {
    EmpManager select(String username);
}

4.3.6 EmpDao

public interface EmpDao {
    int insert(Emp emp);
    int delete(int id);
    int update(Emp emp);
    Emp select(int id);
    //分页查询所有
    List<Emp> selectAll(Page page);
    //查询数据总行数
    long selectCounts();
}

4.3.7 EmpManagerDaoImpl

public class EmpManagerDaoImpl implements EmpManagerDao {
    private QueryRunner queryRunner = new QueryRunner();
    @Override
    public EmpManager select(String username) {
        try {
            EmpManager empManager = queryRunner.query(DbUtils.getConnection(), "select * from empManager where username=?", new BeanHandler<EmpManager>(EmpManager.class), username);

            return empManager;
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }

        return null;
    }
}

4.3.8 EmpDaoImpl

package com.dz.dao.impl;

import com.dz.dao.EmpDao;
import com.dz.entity.Emp;
import com.dz.entity.Page;
import com.dz.utils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
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 EmpDaoImpl implements EmpDao {
    private QueryRunner queryRunner = new QueryRunner();
    @Override
    public int insert(Emp emp) {
        try {
            return queryRunner.update(DbUtils.getConnection(), "insert into emp(name,salary,age) values(?,?,?)", emp.getName(), emp.getSalary(), emp.getAge());
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return 0;
    }

    @Override
    public int delete(int id) {
        try {
            return queryRunner.update(DbUtils.getConnection(),"delete from emp where id=?",id);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return 0;
    }

    @Override
    public int update(Emp emp) {
        try {
            return queryRunner.update(DbUtils.getConnection(),"update emp set name=?,salary=?,age=? where id=?",emp.getName(),emp.getSalary(),emp.getAge(),emp.getId());
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return 0;
    }

    @Override
    public Emp select(int id) {
        try {
            return queryRunner.query(DbUtils.getConnection(),"select * from emp where id=?",new BeanHandler<Emp>(Emp.class),id);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return null;
    }

    @Override
    public List<Emp> selectAll(Page page) {
        try {
            return queryRunner.query(DbUtils.getConnection(),"select * from emp limit ?,?",new BeanListHandler<Emp>(Emp.class),page.getBeginRow(),page.getPageSize());
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return null;
    }

    @Override
    public long selectCounts() {
        try {
            return queryRunner.query(DbUtils.getConnection(),"select count(*) from emp",new ScalarHandler<>());
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return 0;
    }
}

4.3.9 EmpManagerService

public interface EmpManagerService {
    EmpManager login(String username,String password);
}

4.3.10 EmpService

public interface EmpService {
    int addEmp(Emp emp);
    int removeEmp(int id);
    int modifyEmp(Emp emp);
    Emp showEmp(int id);
    List<Emp> showAllEmp(Page page);
}

4.3.11 EmpManagerServiceImpl

public class EmpManagerServiceImpl implements EmpManagerService {
    private EmpManagerDao empManagerDao = new EmpManagerDaoImpl();
    @Override
    public EmpManager login(String username, String password) {
        EmpManager empManager = null;
        try {
            DbUtils.begin();
            EmpManager temp = empManagerDao.select(username);
            if (temp != null) {
                if (temp.getPassword().equals(password)) {
                    empManager = temp;
                }
            }
            DbUtils.commit();
        } catch (Exception e) {
            DbUtils.rollback();
            e.printStackTrace();
        }

        return empManager;
    }
}

4.3.12 EmpServiceImpl

public class EmpServiceImpl implements EmpService {
    private EmpDao empDao = new EmpDaoImpl();
    @Override
    public int addEmp(Emp emp) {
        int result = 0;
        try {
            DbUtils.begin();
            result = empDao.insert(emp);
            DbUtils.commit();
        } catch (Exception e) {
            DbUtils.rollback();
            e.printStackTrace();
        }
        return result;
    }

    @Override
    public int removeEmp(int id) {
        int result = 0;
        try {
            DbUtils.begin();
            result = empDao.delete(id);
            DbUtils.commit();
        } catch (Exception e) {
            DbUtils.rollback();
            e.printStackTrace();
        }
        return result;
    }

    @Override
    public int modifyEmp(Emp emp) {
        int result = 0;
        try {
            DbUtils.begin();
            result = empDao.update(emp);
            DbUtils.commit();
        } catch (Exception e) {
            DbUtils.rollback();
            e.printStackTrace();
        }
        return result;
    }

    @Override
    public Emp showEmp(int id) {
        Emp emp = null;
        try {
            DbUtils.begin();
            emp = empDao.select(id);
            DbUtils.commit();
        } catch (Exception e) {
            DbUtils.rollback();
            e.printStackTrace();
        }
        return emp;
    }

    @Override
    public List<Emp> showAllEmp(Page page) {
        List<Emp> empList = new ArrayList<>();
        try {
            DbUtils.begin();
            long counts = empDao.selectCounts();
            page.setTotalCounts((int)counts);//赋值总条数,计算总页数
            empList = empDao.selectAll(page);
            DbUtils.commit();
        } catch (Exception e) {
            DbUtils.rollback();
            e.printStackTrace();
        }
        return empList;
    }
}

4.3.13 login.jsp

<%@ page import="java.util.Date" %>
<%@ page import="java.time.LocalDate" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>
<head>
    <title>登陆页面</title>
    <link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath}/css/style.css" />
</head>
<body>
<div id="wrap">
    <div id="top_content">
        <div id="header">
            <div id="rightheader">
                <p>
                    <%=LocalDate.now()%> <br />
                </p>
            </div>
            <div id="topheader">
                <h1 id="title">
                    <a href="#">管理员登陆</a>
                </h1>
            </div>
            <div id="navigation"></div>
        </div>
        <div id="content">
            <p id="whereami"></p>
            <h1>login</h1>
            <form action="${pageContext.request.contextPath}/manager/empManagerLogin" method="post">
                <table cellpadding="0" cellspacing="0" border="0"
                       class="form_table">
                    <tr>
                        <td valign="middle" align="right">用户名:</td>
                        <td valign="middle" align="left"><input type="text"
                                                                class="inputgri" name="username" /></td>
                    </tr>
                    <tr>
                        <td valign="middle" align="right">密码:</td>
                        <td valign="middle" align="left"><input type="password"
                                                                class="inputgri" name="password" /></td>
                    </tr>
                    <tr>
                        <td valign="middle" align="right">验证码:</td>
                        <td valign="middle" align="left"><input type="text"
                                                                class="inputgri" name="validateCode" /><img src="${pageContext.request.contextPath}/createCode"
                                                                                                            alt="验证码"></td>
                    </tr>
                </table>
                <p>
                    <input type="submit" class="button" value="Submit &raquo;" />
                </p>
            </form>
        </div>
    </div>
    <div id="footer">
        <div id="footer_bg">EMS/login.jsp</div>
    </div>
</div>
</body>
</html>

4.3.14 empList.jsp

<%@ page import="java.time.LocalDate" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>用户列表</title>
    <link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath}/css/style.css" />
</head>
<body>
<div id="wrap">
    <div id="top_content">
        <div id="header">
            <div id="rightheader">
                <p>
                    <%=LocalDate.now()%>
                    <br />
                </p>
            </div>
            <div id="topheader">
                <h1 id="title">
                    <a href="#">员工列表</a>
                </h1>
            </div>
            <div id="navigation">
            </div>
        </div>
        <div id="content">
            <p id="whereami">
            </p>
            <h1>
                ${empManager.username},Welcome!
            </h1>
            <table class="table">
                <tr class="table_header">
                    <td>
                        ID
                    </td>
                    <td>
                        Name
                    </td>
                    <td>
                        Salary
                    </td>
                    <td>
                        Age
                    </td>
                    <td>
                        Operation
                    </td>
                </tr>
                <%--隔行变色--%>
                <c:forEach var="emp" items="${empList}" varStatus="e">
                    <c:if test="${e.count % 2 != 0}">
                        <tr class="row1">
                    </c:if>
                    <c:if test="${e.count % 2 == 0}">
                        <tr class="row2">
                    </c:if>

                        <td>
                            ${emp.id}
                        </td>
                        <td>
                            ${emp.name}
                        </td>
                        <td>
                            ${emp.salary}
                        </td>
                        <td>
                            ${emp.age}
                        </td>
                        <td>
                            <a href="<c:url context=‘${pageContext.request.contextPath}‘ value=‘/manager/safe/removeEmp?id=${emp.id}‘/> ">delete emp</a>&nbsp;<a href="<c:url context=‘${pageContext.request.contextPath}‘ value=‘/manager/safe/showEmp?id=${emp.id}‘/> ">update emp</a>
                        </td>
                    </tr>
                </c:forEach>
                <tr>
                    <td colspan="5">
                        <a href="<c:url context=‘${pageContext.request.contextPath}‘ value=‘/manager/safe/showAllEmp?pageIndex=1‘/> ">首页</a>
                        <c:if test="${page.pageIndex > 1}">
                            <a href="<c:url context=‘${pageContext.request.contextPath}‘ value=‘/manager/safe/showAllEmp?pageIndex=${page.pageIndex-1}‘/> ">上一页</a>
                        </c:if>
                        <c:if test="${page.pageIndex == 1}">
                            <a>上一页</a>
                        </c:if>
                        <c:if test="${page.pageIndex < page.totalPages}">
                            <a href="<c:url context=‘${pageContext.request.contextPath}‘ value=‘/manager/safe/showAllEmp?pageIndex=${page.pageIndex+1}‘/> ">下一页</a>
                        </c:if>
                        <c:if test="${page.pageIndex == page.totalPages}">
                            <a>下一页</a>
                        </c:if>
                        <a href="<c:url context=‘${pageContext.request.contextPath}‘ value=‘/manager/safe/showAllEmp?pageIndex=${page.totalPages}‘/> ">尾页</a>
                    </td>
                </tr>
            </table>
            <p>
                <input type="button" class="button" value="Add Employee" onclick="location=‘${pageContext.request.contextPath}/manager/safe/addEmp.jsp‘"/>
            </p>
        </div>
    </div>
    <div id="footer">
        <div id="footer_bg">
            empList.jsp
        </div>
    </div>
</div>
</body>
</html>

4.3.15 addEmp.jsp

<%@ page import="java.time.LocalDate" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>新增员工界面</title>
    <link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath}/css/style.css" />
</head>
<body>
<div id="wrap">
    <div id="top_content">
        <div id="header">
            <div id="rightheader">
                <p>
                    <%=LocalDate.now()%>
                    <br />
                </p>
            </div>
            <div id="topheader">
                <h1 id="title">
                    <a href="#">新增员工</a>
                </h1>
            </div>
            <div id="navigation">
            </div>
        </div>
        <div id="content">
            <p id="whereami">
            </p>
            <h1>
                add Emp info:
            </h1>
            <form action="${pageContext.request.contextPath}/manager/safe/addEmp" method="post">
                <table cellpadding="0" cellspacing="0" border="0"
                       class="form_table">
                    <tr>
                        <td valign="middle" align="right">
                            name:
                        </td>
                        <td valign="middle" align="left">
                            <input type="text" class="inputgri" name="name" />
                        </td>
                    </tr>
                    <tr>
                        <td valign="middle" align="right">
                            salary:
                        </td>
                        <td valign="middle" align="left">
                            <input type="text" class="inputgri" name="salary" />
                        </td>
                    </tr>
                    <tr>
                        <td valign="middle" align="right">
                            age:
                        </td>
                        <td valign="middle" align="left">
                            <input type="text" class="inputgri" name="age" />
                        </td>
                    </tr>
                </table>
                <p>
                    <input type="submit" class="button" value="Confirm" />
                </p>
            </form>
        </div>
    </div>
    <div id="footer">
        <div id="footer_bg">
            addEmp.jsp
        </div>
    </div>
</div>
</body>
</html>

4.3.16 EmpManagerLoginController

@WebServlet(name = "EmpManagerLoginController",value = "/manager/empManagerLogin")
public class EmpManagerLoginController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String inputVCode = request.getParameter("validateCode");
        String code = (String) request.getSession().getAttribute("code");

        if (!inputVCode.isEmpty() && inputVCode.equalsIgnoreCase(code)) {
            EmpManagerService empManagerService = new EmpManagerServiceImpl();
            EmpManager empManager = empManagerService.login(username, password);
            if (empManager != null) {
                HttpSession session = request.getSession();
                session.setAttribute("empManager",empManager);

                response.sendRedirect(request.getContextPath() + "/manager/safe/showAllEmp");
            }else {
                response.sendRedirect(request.getContextPath() + "/login.jsp");
            }
        }else {
            response.sendRedirect(request.getContextPath() + "/login.jsp");
        }

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

4.3.17 CreateCodeController

@WebServlet(name = "CreateCodeController",value = "/createCode")
public class CreateCodeController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ValidateCode validateCode = new ValidateCode(200,30,4,10);
        String code = validateCode.getCode();
        HttpSession session = request.getSession();
        session.setAttribute("code",code);

        validateCode.write(response.getOutputStream());

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

4.3.18 ShowAllEmpController

@WebServlet(name = "ShowAllEmpController",value = "/manager/safe/showAllEmp")
public class ShowAllEmpController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String pageIndex = request.getParameter("pageIndex");
        if (pageIndex == null) {
            pageIndex = "1";
        }
        Page page = new Page(Integer.valueOf(pageIndex));

        EmpService empService = new EmpServiceImpl();
        List<Emp> empList = empService.showAllEmp(page);
        if (empList != null) {
            request.setAttribute("page",page);
            request.setAttribute("empList",empList);
            request.getRequestDispatcher("/manager/safe/empList.jsp").forward(request, response);
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

4.3.19 AddEmpController

@WebServlet(name = "AddEmpController",value = "/manager/safe/addEmp")
public class AddEmpController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String name = request.getParameter("name");
        Double salary = Double.valueOf(request.getParameter("salary"));
        Integer age = Integer.valueOf(request.getParameter("age"));

        Emp emp = new Emp(name,salary,age);

        EmpService empService = new EmpServiceImpl();
        empService.addEmp(emp);

        response.sendRedirect(request.getContextPath()+"/manager/safe/showAllEmp");

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

4.3.20 RemoveEmpController

@WebServlet(name = "RemoveEmpController",value = "/manager/safe/removeEmp")
public class RemoveEmpController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Integer id = Integer.valueOf(request.getParameter("id"));

        EmpService empService = new EmpServiceImpl();
        empService.removeEmp(id);
        response.sendRedirect(request.getContextPath() + "/manager/safe/showAllEmp");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

4.3.21 ShowEmpController

@WebServlet(name = "ShowEmpController",value = "/manager/safe/showEmp")
public class ShowEmpController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Integer id = Integer.valueOf(request.getParameter("id"));

        EmpService empService = new EmpServiceImpl();
        Emp emp = empService.showEmp(id);

        request.setAttribute("emp",emp);
        request.getRequestDispatcher("/manager/safe/updateEmp.jsp").forward(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

4.3.22 UpdateEmpController

@WebServlet(name = "UpdateEmpController",value = "/manager/safe/updateEmp")
public class UpdateEmpController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //收参
        Integer id = Integer.valueOf(request.getParameter("id"));
        String name = request.getParameter("name");
        Double salary = Double.valueOf(request.getParameter("salary"));
        Integer age = Integer.valueOf(request.getParameter("age"));

        Emp emp = new Emp(id,name,salary,age);

        EmpService empService = new EmpServiceImpl();
        empService.modifyEmp(emp);

        response.sendRedirect(request.getContextPath()+"/manager/safe/showAllEmp");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

4.3.23 EncodingFilter

@WebFilter(filterName = "EncodingFilter",value = "/manager/*")
public class EncodingFilter implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        //设置统一编码格式
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=UTF-8");

        chain.doFilter(req, resp);
    }

    public void init(FilterConfig config) throws ServletException {

    }
}

4.3.24 CheckFilter

@WebFilter(filterName = "CheckFilter",value = "/manager/safe/*")
public class CheckFilter implements Filter {
    public void destroy() {
    }

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

        HttpSession session = request.getSession();
        EmpManager empManager = (EmpManager) session.getAttribute("empManager");
        if (empManager != null) {
            chain.doFilter(request, response);
        }else {
            response.sendRedirect(request.getContextPath()+"/login.jsp");
        }

    }

    public void init(FilterConfig config) throws ServletException {

    }
}

五. Web开发总结

5.1 开发流程

在Web开发流程中, 遵守以下开发顺序:

DAO
- table
- entity
- DAO接口
- DAO实现
Service
- Service接口
- Service实现(调用DAO实现类, 并控制事务)
Controller(处理请求的Servlet)
- 收集请求中的数据
- 调用业务功能(调用Service实现类)
- 在相应合适的作用域中存储数据
- 流程跳转(forward|sendRedirect)--->.jsp
JSP
- 在作用域中获取数据
- 使用EL+JSTL将数据嵌套在HTML标签中
Filter
- EncodingFilter: 统一编码格式过滤器
- CheckFilter: 权限验证过滤器

8_文件上传与下载

原文：https://www.cnblogs.com/MRASdoubleZ/p/14674470.html

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