文件上传下载

来源：互联网发布：济南行知小学怎么样编辑：程序博客网时间：2024/06/16 18:11

一、文件上传
Upload.html

<formaction="upload"method="post" enctype="multipart/form-data"><inputtype="file"name="file"><inputtype="submit"value="上传"></form>

http://commons.apache.org/proper/commons-fileupload/using.html
UploadServlet.java
使用 apache 提供的 commons-io 和 commons-fileupload 包

package com.keving.upload;import java.io.File;import java.io.IOException;import java.util.List;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.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;/* * 文档的代码 */public class UploadServlet02 extends HttpServlet {    @Override    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // 获取上下文路径        String path = req.getServletContext().getRealPath("/");        // System.out.println(path);        // 1、创建文件条目工厂        DiskFileItemFactory factory = new DiskFileItemFactory();        // 2、设置缓存大小        factory.setSizeThreshold(3 * 1024);        // 3、设置临时目录,该步骤可以省略        File temp = new File(path, "temp");        if (!temp.exists()) {            temp.mkdirs();        }        factory.setRepository(temp);        // 4、上传处理        ServletFileUpload upload = new ServletFileUpload(factory);        // 5、最大限制        upload.setFileSizeMax(3 * 1024 * 1024);        upload.setHeaderEncoding("utf-8");        try {            List<FileItem> items = upload.parseRequest(req);            if (null != items) {                for (FileItem item : items) {                    // 如果不是普通表单并且已选择上传内容则处理                    if (!item.isFormField() && item.getName() != null && !item.getName().equals("")) {                        String fileName = item.getName();                        // String filePath = path + "/upload/"+fileName;                        File uploader = new File(path + "/upload/");                        if (!uploader.exists()) {                            uploader.mkdirs();                        }                        item.write(new File(uploader, fileName));                    }                }            }        } catch (FileUploadException e) {            // TODO Auto-generated catch block        } catch (Exception e) {            // TODO Auto-generated catch block        }    }}

二、文件下载
文件的下载有两种方式:
⑴利用超链接的方式下载
缺点：只有不认识的内容即浏览器不能直接打开的内容浏览器会自动下载；当浏览器
碰见自己能认识的/能打开的内容时，就会直接显示出来
⑵利用第三方下载方式
①获取要下载的文件名
②相对路径转绝对路径
③向响应的头部添加信息

download.html

<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title></head><body><a href="img/dog.jpg">jpg</a><a href="bigdownload?filename01=007.pdf">download</a></body></html>

BigFileDownloadServlet

String filename = request.getParameter("filename01");//      String filename = request.getParameter("007.pdf");        System.out.println(filename);        String path = request.getServletContext().getRealPath("/img/"+filename);         response.setHeader("content-disposition", "attachment;fielname="+filename);        File file = new File(path);        if(file.exists()){            FileInputStream is = new FileInputStream(file);            ServletOutputStream os = response.getOutputStream();            byte[] bs = new byte[1024];            int len = -1;            while(-1!=(len = (is.read(bs)))){                os.write(bs,0,len);            }            os.flush();            os.close();            is.close();        } else {            System.out.println("文件路径找不到");        }

ImgDownloadServlet

//      response.setContentType("application/x-msdownload");//      response.addHeader("content-disposition","attachment;filename=dog.jpg");        response.setContentType("octet-stream");        InputStream is = request.getServletContext().getResourceAsStream("/img/dog.jpg");        BufferedInputStream input =  new BufferedInputStream(is);        ServletOutputStream os = response.getOutputStream();        byte[] bytes = new byte[input.available()];        input.read(bytes);        os.write(bytes);        input.close();        os.close();

PdfDownloadServlet

response.setContentType("application/pdf");        String path = getServletContext().getRealPath("/img/003常用对象.pdf");        System.out.println("path    "+path);        File file = new File(path);        String filename = file.getName();        System.out.println("filename    "+filename);        response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(filename,"UTF-8"));

浏览器显示图片

response.setContentType("image/png");        OutputStream os = response.getOutputStream();        String sourcePath = request.getServletContext().getRealPath("/img/dog.jpg");        InputStream is = new FileInputStream(new File(sourcePath));        byte[] bs = new byte[1024];         int len = -1;        while(-1!=(len=is.read(bs))){            os.write(bs,0,len);        }        os.flush();        os.close();        is.close();

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