java 断点续传 下载_断点续传JAVA实现

支持H5 Video标签播放，迅雷下载

/**

* 断点续传工具

* @author lxycx_xc

* 时间：2017年11月30日

*/

public class BreakpointResume {

private static Logger log = Logger.getLogger(BreakpointResume.class);

/**下载操作，支持断点续传*/

public static void download(HttpServletRequest req,HttpServletResponse resp,String filepath) throws NumberFormatException, IOException{

//请求头参数

File file = new File(filepath);

Long fileSize = file.length();

Long lasttime = file.lastModified();

Long size = fileSize;

int i = 0;

String range = req.getHeader("Range");

String ifm = req.getHeader("If-Modified-Since");

if(ifm!=null&&Long.parseLong(ifm)

resp.setStatus(304);

}else{

byte[] buff = new byte[524288];//1024*1024/2

RandomAccessFile raf = new RandomAccessFile(file, "rw");

BufferedOutputStream bfo = new BufferedOutputStream(resp.getOutputStream());

try {

if(range!=null){//断点续传请求

size = (long)(5242880);//限制每次视频输出的大小

String[] ranges = range.replace("bytes=", "").split("-");

if(ranges.length<2){//为Content-Range参数做铺垫

ranges = new String[]{ranges[0],"0"};

if(fileSize-Long.parseLong(ranges[0])>size){

ranges[1] = String.valueOf(Long.parseLong(ranges[0])+size);

}else{

ranges[1] = String.valueOf(fileSize-1);

}

}

raf.seek(Long.parseLong(ranges[0]));//从指定位置开始读取

resp.setHeader("Last-Modified", String.valueOf(lasttime));//文件最后修改时间

resp.setHeader("Content-Range", "bytes "+StringUtils.join(ranges, "-")+"/"+fileSize);//请求的数据 开始-结束/文件总大小

resp.setStatus(206);

}

int len = 0;

while((len=raf.read(buff))>0&&i

bfo.write(buff);

bfo.flush();

i+=len;

log.debug("本次输出："+buff.length);

}

} catch (Exception e) {

log.info("输出流非正常关闭：");

} finally{

raf.close();

bfo.close();

log.info("当前请求共输出："+i);

}

}

}

}