JAVAWEB之文件的上传下载

文件上传下载

文件上传:

本篇文章使用的文件上传的例子使用的都是原生技术，servelt+jdbc+fileupload插件，这也是笔者的习惯，当接触到某些从未接触过的东西时，总是喜欢用最原始的东西将他们表达出来。下面是具体的步骤，大家可以跟着我一步一步的用apache的fileupload插件来完成文件的上传下载。

1.创建一个web工程，我们这里取名为fileupload

2.导入相关jar包，，数据源使用的是apache-c3p0数据源，以及上传下载插件包，goson库，以及mysql驱动包，大家可以去https://mvnrepository.com/自行下载，系在前请核实jar版本，防止jar冲突。

3.src目录下创建upload.properties文件，用于配置文件上传的限制参数。

 exts=pptx,docx,doc
 file.max.size=1048576
 total.file.max.size=5242880

4.创建工程包结构，

5.创建读取upload.properties的监听器类，初始化上传文件的限制参数，具体代码如下:

 package com.sunyard.listener;

 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Map;
 import java.util.Properties;

 import javax.servlet.ServletContextEvent;
 import javax.servlet.ServletContextListener;

 import com.sunyard.utils.FileUploadAppProperties;

 /**
  * <p>初始化上传文件限制参数的监听器</p>
  * @author:774346810@qq.com
  * @date:2017-6-16
  */
 public class FileUploadAppListener implements ServletContextListener{

     @Override
     public void contextDestroyed(ServletContextEvent arg0) {

     }

     @Override
     public void contextInitialized(ServletContextEvent arg0) {
         InputStream in = this.getClass().getClassLoader().getResourceAsStream("/upload.properties");

         Properties properties = new Properties();

         try {
             properties.load(in);

             for(Map.Entry<Object, Object> prop : properties.entrySet()){
                 String propertyName = (String) prop.getKey();
                 String propertyValue = (String) prop.getValue();

                 FileUploadAppProperties.getInstance().addProperty(propertyName, propertyValue);
             }

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

 }

6.配置web.xml文件

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app version="3.0"
     xmlns="http://java.sun.com/xml/ns/javaee"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
     http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
   <display-name></display-name>
   <welcome-file-list>
     <welcome-file>index.jsp</welcome-file>
   </welcome-file-list>

   <!-- 初始化监听器 -->
   <listener>
       <listener-class>com.sunyard.listener.FileUploadAppListener</listener-class>
   </listener>

   <!-- 注册上传servlet -->
   <servlet>
       <servlet-name>upload</servlet-name>
       <servlet-class>com.sunyard.servlet.FileUploadServlet</servlet-class>
   </servlet>
   <servlet-mapping>
       <servlet-name>upload</servlet-name>
       <url-pattern>/upload</url-pattern>
   </servlet-mapping>

   <!-- 注册下载servlet -->
   <servlet>
      <servlet-name>download</servlet-name>
      <servlet-class>com.sunyard.servlet.DownLoadServlet</servlet-class>
   </servlet>
   <servlet-mapping>
       <servlet-name>download</servlet-name>
       <url-pattern>/download</url-pattern>
   </servlet-mapping>

 </web-app>

配置监听器，以及文件上传servlet和文件下载servlet。

6.完善工程所需要的类，

1）创建上传下载实体，FileUploadBean

 package com.sunyard.bean;

 /**
  * <p>文件上传实体</p>
  * @author:774346810@qq.com
  * @date:2017-6-16
  */
 public class FileUploadBean {
     private Integer id;
     // 文件名
     private String fileName;
     // 文件的路径
     private String filePath;
     // 文件的描述
     private String fileDesc;

     public Integer getId() {
         return id;
     }

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

     public String getFileName() {
         return fileName;
     }

     public void setFileName(String fileName) {
         this.fileName = fileName;
     }

     public String getFilePath() {
         return filePath;
     }

     public void setFilePath(String filePath) {
         this.filePath = filePath;
     }

     public String getFileDesc() {
         return fileDesc;
     }

     public void setFileDesc(String fileDesc) {
         this.fileDesc = fileDesc;
     }

     public FileUploadBean(String fileName, String filePath, String fileDesc) {
         super();
         this.fileName = fileName;
         this.filePath = filePath;
         this.fileDesc = fileDesc;
     }

     public FileUploadBean(Integer id, String fileName, String filePath,
             String fileDesc) {
         this.id = id;
         this.fileName = fileName;
         this.filePath = filePath;
         this.fileDesc = fileDesc;
     }

     public FileUploadBean() {

     }
 }

2）dao操作自定义异常类

 package com.sunyard.db;

 public class DBException extends Exception {

     /**
      *
      */
     private static final long serialVersionUID = -1547402862446161034L;

     public DBException() {
     }

     public DBException(String msg) {
         super(msg);
     }

     public DBException(String msg, Exception ex) {
         super(msg, ex);
     }
 }

3）JDBC连接工具类

 package com.sunyard.db;

 import java.io.InputStream;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.Properties;

 public class JDBCUtils {
     public static void release(ResultSet rs,
             Statement statement, Connection conn) {
         if(rs != null){
             try {
                 rs.close();
             } catch (SQLException e) {
                 e.printStackTrace();
             }
         }

         if (statement != null) {
             try {
                 statement.close();
             } catch (Exception e2) {
                 e2.printStackTrace();
             }
         }

         if (conn != null) {
             try {
                 conn.close();
             } catch (Exception e2) {
                 e2.printStackTrace();
             }
         }
     }

     /**
      * 关闭 Statement 和 Connection
      * @param statement
      * @param conn
      */
     public static void release(Statement statement, Connection conn) {
         if (statement != null) {
             try {
                 statement.close();
             } catch (Exception e2) {
                 e2.printStackTrace();
             }
         }

         if (conn != null) {
             try {
                 conn.close();
             } catch (Exception e2) {
                 e2.printStackTrace();
             }
         }
     }

     /**
      * 1. 获取连接的方法. 通过读取配置文件从数据库服务器获取一个连接.
      *
      * @return
      * @throws Exception
      */
     public static Connection getConnection() throws Exception {
         // 1. 准备连接数据库的 4 个字符串.
         // 1). 创建 Properties 对象
         Properties properties = new Properties();

         // 2). 获取 jdbc.properties 对应的输入流
         InputStream in = JDBCUtils.class.getClassLoader().getResourceAsStream(
                 "jdbc.properties");

         // 3). 加载 2） 对应的输入流
         properties.load(in);

         // 4). 具体决定 user, password 等4 个字符串.
         String user = properties.getProperty("user");
         String password = properties.getProperty("password");
         String jdbcUrl = properties.getProperty("jdbcUrl");
         String driver = properties.getProperty("driver");

         // 2. 加载数据库驱动程序(对应的 Driver 实现类中有注册驱动的静态代码块.)
         Class.forName(driver);

         // 3. 通过 DriverManager 的 getConnection() 方法获取数据库连接.
         return DriverManager.getConnection(jdbcUrl, user, password);
     }
 }

5）文件上传下载的dao层方法

 package com.sunyard.db;

 import java.sql.Connection;
 import java.sql.ResultSet;
 import java.util.ArrayList;
 import java.util.List;

 import com.mysql.jdbc.PreparedStatement;
 import com.mysql.jdbc.Statement;
 import com.sunyard.bean.FileUploadBean;

 /**
  * <p>文件上传下载dao</p>
  * @author:774346810@qq.com
  * @date:2017-6-25
  */
 public class UploadFileDao {

     /**
      * 查询所有文件信息
      * @return
      */
     public List<FileUploadBean> getFiles(){
         Connection conn = null;
         Statement statement = null;
         ResultSet rs = null;

         List<FileUploadBean> beans = new ArrayList<FileUploadBean>();

         try {
             conn = JDBCUtils.getConnection();
             String sql = "SELECT id, file_name fileName, file_path filePath, " +
                     "file_desc fileDesc FROM upload_files";
             statement = (Statement) conn.createStatement();
             rs = statement.executeQuery(sql);

             while(rs.next()){
                 Integer id = rs.getInt("id");
                 String fileName = rs.getString("file_name");
                 String filePath = rs.getString("file_path");
                 String fileDesc = rs.getString("file_desc");

                 FileUploadBean bean = new FileUploadBean(id, fileName, filePath, fileDesc);
                 beans.add(bean);
             }
         } catch (Exception e) {
             e.printStackTrace();
         } finally{
             JDBCUtils.release(rs, statement, conn);
         }

         return beans;
     } 

     /**
      * 将已经上传的文件存放数据库中
      * @param uploadFiles
      */
     public void save(List<FileUploadBean> uploadFiles){

         Connection conn = null;
         PreparedStatement preparedStatement = null;

         try {
             conn = JDBCUtils.getConnection();
             String sql = "INSERT INTO upload_files (file_name, file_path, file_desc) VALUES " +
                     "(?, ?, ?)";
             preparedStatement = (PreparedStatement) conn.prepareStatement(sql);

             for(int i = 0;i < uploadFiles.size();i++){
                 FileUploadBean fileUploadBean = uploadFiles.get(i);
                 preparedStatement.setString(1, fileUploadBean.getFileName());
                 preparedStatement.setString(2, fileUploadBean.getFilePath());
                 preparedStatement.setString(3, fileUploadBean.getFileDesc());
                 preparedStatement.executeUpdate();
             }

         } catch (Exception e) {
             e.printStackTrace();
         } finally{
             JDBCUtils.release(null, preparedStatement, conn);
         }

     }
 }

6）自定义异常类

 package com.sunyard.exception;

 public class InvalidExtNameException extends RuntimeException{

     /**
      *
      */
     private static final long serialVersionUID = -1478119693559275850L;

     public InvalidExtNameException(String msg){
         super(msg);
     }
 }

7）处理文件上传的servlet

 package com.sunyard.servlet;

 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.UnsupportedEncodingException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.apache.commons.fileupload.FileItem;
 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
 import org.apache.commons.fileupload.servlet.ServletFileUpload;

 import com.sunyard.bean.FileUploadBean;
 import com.sunyard.db.UploadFileDao;
 import com.sunyard.exception.InvalidExtNameException;
 import com.sunyard.utils.FileUploadAppProperties;

 public class FileUploadServlet extends HttpServlet{

     private static final long serialVersionUID = 6227133615299280663L;

     private static final String FILE_PATH = "/WEB-INF/files/";//类路径

     private static final String TEMP_DIR = "d:\\tempDirectory";//文件临时存储路径

     UploadFileDao uploadFileDao = new UploadFileDao();

     @Override
     protected void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         request.setCharacterEncoding("UTF-8");

         String path = null;

         //获取 ServletFileUpload 对象.
         ServletFileUpload upload = getServletFileUpload();

         try {
             //把需要上传的 FileItem 都放入到该 Map 中
             //键: 文件的待存放的路径, 值: 对应的 FileItem 对象
             Map<String, FileItem> uploadFiles = new HashMap<String, FileItem>();

             //解析请求, 得到 FileItem 的集合.
             List<FileItem> items = upload.parseRequest(request);

             //1. 构建 FileUploadBean 的集合, 同时填充 uploadFiles
             List<FileUploadBean> beans = buildFileUploadBeans(items, uploadFiles);

             //2. 校验扩展名:
             vaidateExtName(beans);

             //3. 校验文件的大小: 在解析时, 已经校验了, 我们只需要通过异常得到结果. 

             //4. 进行文件的上传操作.
             upload(uploadFiles);

             //5. 把上传的信息保存到数据库中
             saveBeans(beans);

             path = "/app/success.jsp";
         } catch (Exception e) {
             e.printStackTrace();
         }

         request.getRequestDispatcher(path).forward(request, response);
     }

     private void saveBeans(List<FileUploadBean> beans) {
         uploadFileDao.save(beans);
     }

     /**
      * 进行文件上传操作
      * @param uploadFiles
      * @throws IOException
      */
     private void upload(Map<String, FileItem> uploadFiles) throws IOException {
         for(Map.Entry<String, FileItem> uploadFile: uploadFiles.entrySet()){
             String filePath = uploadFile.getKey();
             FileItem item = uploadFile.getValue();

             upload(filePath, item.getInputStream());
         }
     }

     /**
      * 文件上传的 IO 方法.
      *
      * @param filePath
      * @param inputStream
      * @throws IOException
      */
     private void upload(String filePath, InputStream inputStream) throws IOException {
         OutputStream out = new FileOutputStream(filePath);

         byte [] buffer = new byte[1024];
         int len = 0;

         while((len = inputStream.read(buffer)) != -1){
             out.write(buffer, 0, len);
         }

         inputStream.close();
         out.close();

         System.out.println(filePath);
     }

     /**
      * 校验文件扩展名是否合法
      * @param beans
      */
     private void vaidateExtName(List<FileUploadBean> beans) {
         String exts = FileUploadAppProperties.getInstance().getProperty("exts");
         List<String> extList = Arrays.asList(exts.split(","));
         System.out.println(extList);

         for(FileUploadBean bean: beans){
             String fileName = bean.getFileName();
             System.out.println(fileName.indexOf(".")); 

             String extName = fileName.substring(fileName.lastIndexOf(".") + 1);
             System.out.println(extName); 

             if(!extList.contains(extName)){
                 throw new InvalidExtNameException(fileName + "文件的扩展名不合法");
             }
         }
     }

     /**
      * 利用传入的 FileItem 的集合, 构建 FileUploadBean 的集合, 同时填充 uploadFiles
      *
      * FileUploadBean 对象封装了: id, fileName, filePath, fileDesc
      * uploadFiles: Map<String, FileItem> 类型, 存放文件域类型的  FileItem. 键: 待保存的文件的名字 ,值: FileItem 对象
      *
      * 构建过程:
      * 1. 对传入 FileItem 的集合进行遍历. 得到 desc 的那个 Map. 键: desc 的 fieldName(desc1, desc2 ...).
      * 值: desc 的那个输入的文本值
      *
      * 2. 对传入 FileItem 的集合进行遍历. 得到文件域的那些 FileItem 对象, 构建对应的 key (desc1 ....) 来获取其 desc.
      * 构建的 FileUploadBean 对象, 并填充 beans 和 uploadFiles
      *
      * @param items
      * @param uploadFiles
      * @return
      * @throws UnsupportedEncodingException
      */
     private List<FileUploadBean> buildFileUploadBeans(List<FileItem> items,
             Map<String, FileItem> uploadFiles) throws UnsupportedEncodingException {
         List<FileUploadBean> beans = new ArrayList<FileUploadBean>();

         Map<String, String> descs = new HashMap<String, String>();

         //处理普通的表单体
         for(int i = 0;i < items.size();i++){
             FileItem item = items.get(i);

             if(item.isFormField()){
                 //desc1 或 desc2 ...
                 String fieldName = item.getFieldName();
                 String desc = item.getString("UTF-8");

                 descs.put(fieldName, desc);
             }
         }

         //处理文件表单体
         for(int i = 0;i < items.size();i++){
             FileItem item = items.get(i);
             FileUploadBean bean = null;
             if(!item.isFormField()){
                 String fieldName = item.getFieldName();
                 String descName = "desc" + fieldName.substring(fieldName.length() - 1);
                 String desc = descs.get(descName); 

                 //对应文件名
                 String fileName = item.getName();
                 String filePath = getFilePath(fileName);

                 bean = new FileUploadBean(fileName, filePath, desc);
                 beans.add(bean);

                 uploadFiles.put(bean.getFilePath(), item);
             }
         }

         return beans;
     }

     /**
      * 根据跟定的文件名构建一个随机的文件名
      * 1. 构建的文件的文件名的扩展名和给定的文件的扩展名一致
      * 2. 利用 ServletContext 的 getRealPath 方法获取的绝对路径
      * 3. 利用了 Random 和 当前的系统时间构建随机的文件的名字
      *
      * @param fileName
      * @return
      */
     private String getFilePath(String fileName) {
         String extName = fileName.substring(fileName.lastIndexOf("."));
         Random random = new Random();

         String filePath = getServletContext().getRealPath(FILE_PATH) + "\\" + System.currentTimeMillis() + random.nextInt(100000) + extName;
         return filePath;
     }

     /**
      * 获取 ServletFileUpload 对象.
      * @return
      */
     private ServletFileUpload getServletFileUpload(){
         String fileMaxSize = FileUploadAppProperties.getInstance().getProperty("file.max.size");
         String totalFileMaxSize = FileUploadAppProperties.getInstance().getProperty("total.file.max.size");

         DiskFileItemFactory factory = new DiskFileItemFactory();

         factory.setSizeThreshold(1024 * 500);
         File tempDirectory = new File(TEMP_DIR);
         factory.setRepository(tempDirectory);

         ServletFileUpload upload = new ServletFileUpload(factory);

         upload.setSizeMax(Integer.parseInt(totalFileMaxSize));
         upload.setFileSizeMax(Integer.parseInt(fileMaxSize));

         return upload;
     }

 }

8）用于存储文件上传的单例工具类FileUploadAppProperties

 package com.sunyard.utils;

 import java.util.HashMap;
 import java.util.Map;

 /**
  * <p>上传下载参数单例类</p>
  * @author:774346810@qq.com
  * @date:2017-6-16
  */
 public class FileUploadAppProperties {

     private Map<String, String> properties = new HashMap<String, String>();

     private FileUploadAppProperties(){}

     private static FileUploadAppProperties instance = new FileUploadAppProperties();

     public static FileUploadAppProperties getInstance(){
         return instance;
     }

     public void addProperty(String propertyName,String propertyValue){
         properties.put(propertyName, propertyValue);
     }

     public String getProperty(String propertyName){
         return properties.get(propertyName);
     }
 }

9）JDBC连接数据库的参数properties文件

 #driver=oracle.jdbc.driver.OracleDriver
 #jdbcUrl=jdbc:oracle:thin:@localhost:1521:orcl
 #user=scott
 #password=java

 driver=com.mysql.jdbc.Driver
 jdbcUrl=jdbc:mysql://localhost:3306/upload
 user=root
 password=123456

10）jQuery开发的静态资源文件

11）文件上传的页面upload.jsp

 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
 <%
 String path = request.getContextPath();
 String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
 %>

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 <html>
   <head>
     <base href="<%=basePath%>">

     <title>My JSP 'upload.jsp' starting page</title>

     <meta http-equiv="pragma" content="no-cache">
     <meta http-equiv="cache-control" content="no-cache">
     <meta http-equiv="expires" content="0">
     <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
     <meta http-equiv="description" content="This is my page">
     <!--
     <link rel="stylesheet" type="text/css" href="styles.css">
     -->
     <script type="text/javascript" src="${pageContext.request.contextPath }/scripts/jquery-1.7.2.js"></script>
     <script type="text/javascript">

         $(function(){

             var i = 2;

             $("#addFile").click(function(){
                 $(this).parent().parent().before("<tr class='file'><td>File"
                         + i + ":</td><td><input type='file' name='file"
                         + i + "'/></td></tr>"
                         + "<tr class='desc'><td>Desc"
                         + i + ":</td><td><input type='text' name='desc"
                         + i + "'/><button id='delete"
                         + i + "'>删除</button></td></tr>");
                 i++;

                 //获取新添加的删除按钮
                 $("#delete" + (i-1)).click(function(){
                     var $tr = $(this).parent().parent();
                     $tr.prev("tr").remove();
                     $tr.remove();

                     //对 i 重写排序
                     $(".file").each(function(index){
                         var n = index + 1;

                         $(this).find("td:first").text("File" + n);
                         $(this).find("td:last input").attr("name", "file" + n);
                     });

                     $(".desc").each(function(index){
                         var n = index + 1;

                         $(this).find("td:first").text("Desc" + n);
                         $(this).find("td:last input").attr("name", "desc" + n);
                     });

                     i = i - 1;
                 });

                 return false;
             });

         });

     </script>
   </head>

   <body>
     <font color="red">${message }</font>
     <br><br>

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

         <table>
             <tr class="file">
                 <td>File1:</td>
                 <td><input type="file" name="file1"/></td>
             </tr>
             <tr class="desc">
                 <td>Desc1:</td>
                 <td><input type="text" name="desc1"/></td>
             </tr>

             <tr>
                 <td><input type="submit" id="submit" value="提交"/></td>
                 <td><button id="addFile">新增一个附件</button></td>
             </tr>
         </table>

     </form>
   </body>
 </html>

将项目部署服务器，启动，访问http://127.0.0.1:8080/fileupload/app/upload.jsp后出现下面的页面

点击上传，就可以完成文件上传的功能。

可以去服务器和数据库中查看是否上传成功，如下：

至此，文件上传功能完成。

***************************************************************

文件下载：

为了演示，我们将需要下载的文件内容写死，处理下载的servlet代码如下。

 package com.sunyard.servlet;

 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.URLEncoder;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import com.sunyard.db.UploadFileDao;

 /**
  * <p>下载servlet</p>
  * @author:774346810@qq.com
  * @date:2017-6-18
  */
 public class DownLoadServlet extends HttpServlet{

     private static final long serialVersionUID = -1409324086440387753L;

     @Override
     protected void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         response.setContentType("application/x-msdownload");

         String fileName = "文件下载.docx";
         response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));

         OutputStream out = response.getOutputStream();
         String pptFileName = "D:\\apache-tomcat-6.0.16\\webapps\\fileupload\\WEB-INF\\files\\149837444825180585.docx";

         InputStream in = new FileInputStream(pptFileName);

         byte [] buffer = new byte[1024];
         int len = 0;

         while((len = in.read(buffer)) != -1){
             out.write(buffer, 0, len);
         }

         in.close();
     }

 }

同样，开启服务，打开浏览器访问

既可以得到需要你下载的文件。

至此，文件上传下载的小案例都在这里了。需要下载demo的同学我已经把工程放在我的百度网盘上大家可以自行下载：

http://pan.baidu.com/s/1pLc6Icb