文件上传下载之commons-fileupload

1. 文件上传

   web应用中，经常会使用到文件的上传功能，其中有一些约束条件：

   • 上传文件大小、格式的限制，一般前台js进行限制后，后台同样也需要限制
   • 保证短之间内不让用户上传太多的文件
   • 服务器端对文件结构的管理，不能暴露文件目录
   • 防止文件被同名覆盖
   • 有条件的情况下会和杀毒软件厂家对接，防止用户上传病毒或者恶意代码，比如CKnife

只需要commons-fileupload-1.3.2.jar和commons-io-2.5.jar

直接上代码

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">  <display-name>fileupload_mhm</display-name>  <servlet>    <servlet-name>upload</servlet-name>    <servlet-class>com.mhm.upload.FileUploadServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>upload</servlet-name>    <url-pattern>/upload</url-pattern>  </servlet-mapping>  <welcome-file-list>    <welcome-file>index.html</welcome-file>    <welcome-file>index.htm</welcome-file>    <welcome-file>index.jsp</welcome-file>    <welcome-file>default.html</welcome-file>    <welcome-file>default.htm</welcome-file>    <welcome-file>default.jsp</welcome-file>  </welcome-file-list></web-app>/** * 不用缓冲区的上传 *  * @author MHm * @time 2017年8月10日下午5:15:39 */public class FileUploadServlet extends HttpServlet {    /**     *      */    private static final long serialVersionUID = 1L;    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doPost(req, resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException {        String message = "";        String savePath = this.getServletContext().getRealPath("/WEB-INF/upload");        File srcFile = new File(savePath);        if (!srcFile.exists() && !srcFile.isDirectory()) {            srcFile.mkdir();        }        // 使用commonFile        DiskFileItemFactory factory = new DiskFileItemFactory();        ServletFileUpload upload = new ServletFileUpload(factory);        upload.setHeaderEncoding("utf-8");        if (!ServletFileUpload.isMultipartContent(req)) {            return;        }        InputStream in = null;        FileOutputStream fos = null;        try {            List<FileItem> list = upload.parseRequest(req);            for (FileItem it : list) {                if (it.isFormField()) {                    String name = it.getFieldName();                    String value = it.getString("utf-8");                    System.out.println(name + ":" + value);                } else {                    String filename = it.getName();                    System.out.println(filename);                    if (filename == null || filename.trim().equals("")) {                        continue;                    }                    filename = filename.substring(filename.lastIndexOf("\\") + 1);                    in = it.getInputStream();                    fos = new FileOutputStream(savePath + "\\" + filename);                    byte[] buffer = new byte[1024];                    int len = 0;                    while ((len = in.read(buffer)) > 0) {                        fos.write(buffer, 0, len);                    }                    //                    // 关闭输入流//                    in.close();//                    // 关闭输出流//                    fos.close();                    // 删除处理文件上传时生成的临时文件,关闭流之后再删除临时文件                    it.delete();                    message = message + filename + ":文件上传成功！" + File.separator;                }            }        } catch (FileUploadException e) {            e.printStackTrace();        } catch (UnsupportedEncodingException e) {            e.printStackTrace();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        } finally {            try {                in.close();                fos.close();            } catch (IOException e) {                e.printStackTrace();            }        }        try {            req.setAttribute("message", message);            req.getRequestDispatcher("/pages/message.jsp").forward(req, resp);        } catch (IOException e) {            e.printStackTrace();        }    }}uploadFile.jsp<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body>    <form action="${pageContext.request.contextPath}/upload" enctype="multipart/form-data" method="post">  上传用户：<input type="text" name="username"><br/>  上传文件1：<input type="file" name="file1"><br/>  上传文件2：<input type="file" name="file2"><br/>  <input type="submit" value="提交"> </form></body></html>

message.jsp<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body>${message }</body></html>

使用临时文件管理的方式上传

import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.UnsupportedEncodingException;import java.util.List;import java.util.UUID;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.FileUploadException;import org.apache.commons.fileupload.ProgressListener;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;/** * 带临时目录缓冲区 *  * @author MHm * @time 2017年8月10日下午5:15:39 */public class FileUploadTempServlet extends HttpServlet {    /**     *      */    private static final long serialVersionUID = 1L;    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doPost(req, resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException {        String message = "";        String fileTypeStr = "doc,docx,pdf,txt";        String savePath = this.getServletContext().getRealPath("/WEB-INF/upload");        String tempPath = this.getServletContext().getRealPath("/WEB-INF/temp");        File tempFile = new File(tempPath);        if (!tempFile.exists() && !tempFile.isDirectory()) {            tempFile.mkdir();        }        // 使用commonFile        // 1、创建一个DiskFileItemFactory工厂        DiskFileItemFactory factory = new DiskFileItemFactory();        // 100KB缓冲区        factory.setSizeThreshold(1024 * 100);        // 设置上传时生成的临时文件的保存目录        factory.setRepository(tempFile);        // 2、创建一个文件上传解析器        ServletFileUpload upload = new ServletFileUpload(factory);        // 进度监听器        upload.setProgressListener(new ProgressListener() {            @Override            public void update(long byteRead, long contentLength, int arg2) {                System.out.println("文件大小为：" + contentLength + ",当前已处理：" + byteRead);            }        });        upload.setHeaderEncoding("utf-8");        // 是否普通表单提交        if (!ServletFileUpload.isMultipartContent(req)) {            return;        }        // 设置上传单个文件的大小的最大值，目前是设置为10MB        int fileSizeMax = 1024 * 1024 * 10;        upload.setFileSizeMax(fileSizeMax);        // 设置上传文件总量的最大值，最大值=同时上传的多个文件的大小的最大值的和，目前设置为10MB        int sizeMax = 1024 * 1024 * 10;        upload.setSizeMax(sizeMax);        InputStream in = null;        FileOutputStream fos = null;                try {            List<FileItem> list = upload.parseRequest(req);            for (FileItem it : list) {                if (it.isFormField()) {                    String name = it.getFieldName();                    String value = it.getString("utf-8");                    System.out.println(name + ":" + value);                } else {                    String filename = it.getName();                    if (filename == null || filename.trim().equals("")) {                        continue;                    }                    filename = filename.substring(filename.lastIndexOf("\\") + 1);                    // 扩展名                    String fileExtName = filename.substring(filename.lastIndexOf(".") + 1);                    if (fileTypeStr.indexOf(fileExtName) == -1) {                        System.out.println("上传的文件的扩展名是：" + fileExtName);                        continue;                    }                    String saveFileName = UUID.randomUUID().toString() + "_" + filename;                    String saveFilePathName = buildPath(saveFileName, savePath);                    in = it.getInputStream();                    fos = new FileOutputStream(saveFilePathName + "\\" + saveFileName);                    byte[] buffer = new byte[1024];                    int len = 0;                    while ((len = in.read(buffer)) > 0) {                        fos.write(buffer, 0, len);                    }                    //                    in.close();                    fos.close();                    it.delete();                    message = message + filename + ":文件上传成功！" + File.separator;                }            }            req.setAttribute("message", message);            req.getRequestDispatcher("/pages/message.jsp").forward(req, resp);        } catch (FileUploadException e) {            e.printStackTrace();        } catch (UnsupportedEncodingException e) {            e.printStackTrace();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        } finally {            try {                in.close();                fos.close();            } catch (IOException e) {                e.printStackTrace();            }        }    }    /**     * @param saveFileName     * @param savePath     * @return     */    private String buildPath(String saveFileName, String savePath) {        int hashcode = saveFileName.hashCode();        int dir1 = hashcode & 0xf;        int dir2 = (hashcode & 0xf0) >> 4;        String dir = savePath + "\\" + dir1 + "\\" + dir2;        File file = new File(dir);        if (!file.exists()) {            // 创建目录            file.mkdirs();        }        return dir;    }}

看看效果

2.文件下载

文件列表

<servlet>        <servlet-name>fileList</servlet-name>        <servlet-class>com.mhm.upload.FileListServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>fileList</servlet-name>        <url-pattern>/fileList</url-pattern>    </servlet-mapping>    <servlet>        <servlet-name>download</servlet-name>        <servlet-class>com.mhm.upload.DownloadServlet</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>download</servlet-name>        <url-pattern>/download</url-pattern>    </servlet-mapping>

jsp页面代码

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><!-- 遍历Map集合 --><c:forEach var="me" items="${fileNameMap}"><c:url value="/download" var="downurl"><c:param name="filename" value="${me.key}"></c:param></c:url>${me.value}<a href="${downurl}">下载</a><br/></c:forEach> </form></body></html>

文件列表查询：

/** * @author MHm * @time 2017年8月11日上午11:27:18 */public class FileListServlet extends HttpServlet{    /**     *      */    private static final long serialVersionUID = 2692787517286234116L;    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doPost(req, resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        String uploadFilePath = this.getServletContext().getRealPath("/WEB-INF/upload");        Map<String,String> fileNameMap = new HashMap<String,String>();        listFile(new File(uploadFilePath),fileNameMap);        req.setAttribute("fileNameMap", fileNameMap);        req.getRequestDispatcher("/pages/uploadFile.jsp").forward(req, resp);    }    private void listFile(File file,Map<String,String> map){        if(!file.isFile()){            File[] files = file.listFiles();            for(File f :files){                listFile(f,map);            }        }else{            String real_name = file.getName().substring(file.getName().indexOf("_")+1);            map.put(file.getName(), real_name);        }    }}

文件下载：

package com.mhm.upload;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.IOException;import java.io.OutputStream;import java.io.UnsupportedEncodingException;import java.net.URLEncoder;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * @author MHm * @time 2017年8月11日上午11:36:17 */public class DownloadServlet extends HttpServlet {    /**     *      */    private static final long serialVersionUID = 1L;    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doPost(req, resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException {        FileInputStream in = null;        OutputStream out = null;        try {            String fileName = req.getParameter("filename");            fileName = new String(fileName.getBytes("iso-8859-1"), "utf-8");            String realPath = this.getServletContext().getRealPath("/WEB-INF/upload");            String fileRealPath = buildPath(fileName, realPath);            // 得到要下载的文件            File file = new File(fileRealPath + "\\" + fileName);            // 如果文件不存在            if (!file.exists()) {                req.setAttribute("message", "您要下载的资源已被删除！！");                req.getRequestDispatcher("/pages/message.jsp").forward(req, resp);                return;            }            // 处理文件名            String realname = fileName.substring(fileName.indexOf("_") + 1);            // 设置响应头，控制浏览器下载该文件            resp.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));            // 读取要下载的文件，保存到文件输入流            in = new FileInputStream(fileRealPath + "\\" + fileName);            // 创建输出流            out = resp.getOutputStream();            // 创建缓冲区            byte buffer[] = new byte[1024];            int len = 0;            // 循环将输入流中的内容读取到缓冲区当中            while ((len = in.read(buffer)) > 0) {                // 输出缓冲区的内容到浏览器，实现文件下载                out.write(buffer, 0, len);            }        } catch (UnsupportedEncodingException e) {            e.printStackTrace();        } catch (FileNotFoundException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        } finally {            try {                // 关闭文件输入流                in.close();                // 关闭输出流                out.close();            } catch (IOException e) {                e.printStackTrace();            }        }    }    /**     * @param saveFileName     * @param savePath     * @return     */    private String buildPath(String saveFileName, String savePath) {        int hashcode = saveFileName.hashCode();        int dir1 = hashcode & 0xf;        int dir2 = (hashcode & 0xf0) >> 4;        String dir = savePath + "\\" + dir1 + "\\" + dir2;        File file = new File(dir);        if (!file.exists()) {            // 创建目录            file.mkdirs();        }        return dir;    }}