【文件下载】java下载文件的几种方式（本地下载、从网络上下载、在线浏览）

逃离我推掉我的手 2022-03-02 14:56 305阅读 0赞

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原文地址：[https://www.cnblogs.com/sunny3096/p/8204291.html][https_www.cnblogs.com_sunny3096_p_8204291.html]

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# 1.以流的方式下载. #

public HttpServletResponse download(String path, HttpServletResponse response) { 
            try { 
                // path是指欲下载的文件的路径。
                File file = new File(path);
                // 取得文件名。
                String filename = file.getName();
                // 取得文件的后缀名。
                String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();
    
                // 以流的形式下载文件。
                InputStream fis = new BufferedInputStream(new FileInputStream(path));
                byte[] buffer = new byte[fis.available()];
                fis.read(buffer);
                fis.close();
                // 清空response
                response.reset();
                // 设置response的Header
                response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));
                response.addHeader("Content-Length", "" + file.length());
                OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
                response.setContentType("application/octet-stream");
                toClient.write(buffer);
                toClient.flush();
                toClient.close();
            } catch (IOException ex) { 
                ex.printStackTrace();
            }
            return response;
        }

# 2.下载本地文件. #

public void downloadLocal(HttpServletResponse response) throws FileNotFoundException { 
            // 下载本地文件
            String fileName = "Operator.doc".toString(); // 文件的默认保存名
            // 读到流中
            InputStream inStream = new FileInputStream("c:/Operator.doc");// 文件的存放路径
            // 设置输出的格式
            response.reset();
            response.setContentType("bin");
            response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
            // 循环取出流中的数据
            byte[] b = new byte[100];
            int len;
            try { 
                while ((len = inStream.read(b)) > 0)
                    response.getOutputStream().write(b, 0, len);
                inStream.close();
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }

# 3.下载网络文件. #

public void downloadNet(HttpServletResponse response) throws MalformedURLException { 
            // 下载网络文件
            int bytesum = 0;
            int byteread = 0;
    
            URL url = new URL("windine.blogdriver.com/logo.gif");
    
            try { 
                URLConnection conn = url.openConnection();
                InputStream inStream = conn.getInputStream();
                FileOutputStream fs = new FileOutputStream("c:/abc.gif");
    
                byte[] buffer = new byte[1204];
                int length;
                while ((byteread = inStream.read(buffer)) != -1) { 
                    bytesum += byteread;
                    System.out.println(bytesum);
                    fs.write(buffer, 0, byteread);
                }
            } catch (FileNotFoundException e) { 
                e.printStackTrace();
            } catch (IOException e) { 
                e.printStackTrace();
            }
        }

# 4.支持在线方式打开. #

public void downLoad(String filePath, HttpServletResponse response, boolean isOnLine) throws Exception { 
            File f = new File(filePath);
            if (!f.exists()) { 
                response.sendError(404, "File not found!");
                return;
            }
            BufferedInputStream br = new BufferedInputStream(new FileInputStream(f));
            byte[] buf = new byte[1024];
            int len = 0;
    
            response.reset(); // 非常重要
            if (isOnLine) {  // 在线打开方式
                URL u = new URL("file:///" + filePath);
                response.setContentType(u.openConnection().getContentType());
                response.setHeader("Content-Disposition", "inline; filename=" + f.getName());
                // 文件名应该编码成UTF-8
            } else {  // 纯下载方式
                response.setContentType("application/x-msdownload");
                response.setHeader("Content-Disposition", "attachment; filename=" + f.getName());
            }
            OutputStream out = response.getOutputStream();
            while ((len = br.read(buf)) > 0)
                out.write(buf, 0, len);
            br.close();
            out.close();
        }

[https_www.cnblogs.com_sunny3096_p_8204291.html]: https://www.cnblogs.com/sunny3096/p/8204291.html