Java 下载支持断点续传

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[Java]代码，服务器端实现

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File file = new File(location);                         

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                        if (file.exists()) {                                         

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                            long p = 0; 

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                            long fileLength; 

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                            fileLength = file.length(); 

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                            // get file content 

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                            InputStream ins = new FileInputStream(file); 

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                            bis = new BufferedInputStream(ins);                             

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                            // tell the client to allow accept-ranges 

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                            response.reset(); 

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                            response.setHeader("Accept-Ranges", "bytes"); 

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                            // client requests a file block download start byte 

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                            if (request.getHeader("Range") != null) {                                 

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                                response.setStatus(javax.servlet.http.HttpServletResponse.SC_PARTIAL_CONTENT); 

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                                p = Long.parseLong(request.getHeader("Range") 

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                                        .replaceAll("bytes=", "") 

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                                        .replaceAll("-", "") 

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                                        );                                 

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                            } 

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                            // support multi-threaded download 

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                            // respone format: 

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                            // Content-Length:[file size] - [client request start bytes from file block] 

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                            response.setHeader("Content-Length", new Long(fileLength - p).toString()); 

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                            if (p != 0) { 

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                                // 断点开始 

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                                // 响应的格式是: 

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                                // Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小] 

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                                String contentRange = new StringBuffer("bytes ") 

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                                        .append(new Long(p).toString()) 

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                                        .append("-") 

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                                        .append(new Long(fileLength - 1).toString()) 

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                                        .append("/") 

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                                        .append(new Long(fileLength).toString()) 

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                                        .toString(); 

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                                response.setHeader("Content-Range", contentRange); 

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                                // pointer move to seek 

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                                bis.skip(p); 

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                            } 

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                            String fileName = file.getName(); 

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                            response.addHeader("Content-Disposition", "attachment;filename=" + fileName); 

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                            while ((size = bis.read(buf)) != -1) { 

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                                response.getOutputStream().write(buf,0,size); 

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                                response.getOutputStream().flush();                                 

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                            } 

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                            bis.close();

[代码] 客户端下载测试

 
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public class TestDownload { 

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    /** 

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     * @param args 

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     */

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    public static void main(String[] args) { 

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        // TODO Auto-generated method stub 

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        HttpURLConnection httpURLConnection = null; 

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        URL url = null; 

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        BufferedInputStream bis = null; 

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        byte[] buf = new byte[10240]; 

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        int size = 0; 

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        String fileName = "aaa.zip"; 

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        String filePath = "C:\\Users\\Desktop"; 

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        String remoteUrl = "http://127.0.0.1:8080/down.zip"; 

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        // 检查本地文件 

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        RandomAccessFile rndFile = null; 

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        File file = new File(filePath + "\\" + fileName); 

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        long remoteFileSize = getRemoteFileSzie(remoteUrl); 

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        long nPos = 0; 

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        if (file.exists()) {                        

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            long localFileSzie = file.length(); 

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            if (localFileSzie < remoteFileSize) {                    

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                System.out.println("文件续传..."); 

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                nPos = localFileSzie; 

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            } else { 

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                System.out.println("文件存在，重新下载..."); 

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                file.delete(); 

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                try { 

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                    file.createNewFile(); 

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                } catch (Exception e) { 

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                    // TODO: handle exception 

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                    e.printStackTrace(); 

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                }    

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            } 

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        } else { 

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            // 建立文件 

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            try { 

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                file.createNewFile(); 

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            } catch (Exception e) { 

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                // TODO: handle exception 

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                e.printStackTrace(); 

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            }            

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        } 

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        // 下载文件 

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        try { 

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            url = new URL(remoteUrl);        

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            httpURLConnection = (HttpURLConnection)url.openConnection(); 

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            // 设置User-Agent 

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            httpURLConnection.setRequestProperty("User-Agent", "Net"); 

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            // 设置续传开始 

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            httpURLConnection.setRequestProperty("Range", "bytes=" + nPos + "-"); 

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            // 获取输入流 

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            bis = new BufferedInputStream(httpURLConnection.getInputStream());            

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            rndFile = new RandomAccessFile(filePath + "\\" + fileName, "rw"); 

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            rndFile.seek(nPos); 

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            int i = 0; 

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            while ((size = bis.read(buf)) != -1) { 

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                //if (i > 500) break;                

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                rndFile.write(buf, 0, size); 

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                i++; 

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            } 

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            System.out.println("i=" + i); 

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            httpURLConnection.disconnect(); 

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        } catch (Exception e) { 

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            // TODO: handle exception 

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            e.printStackTrace(); 

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        } 

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    } 

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    public static long getRemoteFileSzie(String url) { 

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        long size = 0; 

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        try { 

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            HttpURLConnection httpUrl = (HttpURLConnection)(new URL(url)).openConnection(); 

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            size = httpUrl.getContentLength(); 

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            httpUrl.disconnect();            

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        } catch (Exception e) { 

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            // TODO: handle exception 

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            e.printStackTrace(); 

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        } 

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        return size; 

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    } 

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}