目前遇到2种场景需要用到断点续传

1. 视频进度条无法正常拖动，或拖动视频未发生变化，F12请求头中可以看到“Range”。
2. 使用B站开源组件flv.js只可以播放3分钟视频，想要解决就需要写一个获取文件的Controller接口，该接口实现断点续传。（如果文件是存储在minio中的，使用minio生成的共享外链即可，不需要自己写断点续传了，minio本身支持断点续传，实际场景是使用apache文件服务器时出现的）

代码如下：

	private final static String SPLITER = "-";
    private final static String STRING_NULL = "null";
    private final static String SLASH = "/";
    private final static String SPACE = " ";
    private final static String BYTES_EQUALS = "bytes=";
    private final static String BYTES_SPACE = "bytes ";
    private final static String BYTES = "bytes";
    private final static String STRING_EQUALS = "=";
    private final static String ZERO_LEFT = "0-";

    /**
     * 默认缓冲区大小4Kb
     */
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    /**
     * 0 从头开始的全文下载
     */
    private static final int RANGE_SWITCH_FULL = 0;
    /**
     * 1 从某字节开始的下载（bytes=[left]-）；
     */
    private static final int RANGE_SWITCH_LEFT_START = 1;
    /**
     * 2 从某字节开始到某字节结束的下载（bytes=[left]-[right]）
     */
    private static final int RANGE_SWITCH_LEFT_TO_RIGHT = 2;

	/**
     * 从minio下载（二选一-1）
     *
     * @param protocol minio协议串
     * @param response http响应
     */
    public void downloadFile(HttpServletRequest request, String protocol, HttpServletResponse response) {
    
        String extension = FilenameUtils.getExtension(protocol);
        String mimeType = MediaType.getMimeType(extension);
        response.setContentType(mimeType);
        if (storeService.exists(protocol)) {
    
            try (InputStream in = storeService.getInputStream(protocol);
                 OutputStream out = response.getOutputStream()) {
    
                if(mimeType.contains("video/") || mimeType.contains("audio/")){
    
                    StorageMetadata metadata = storeService.getMetadata(protocol);
                    ddxcDownload(request, response, in, out, String.valueOf(metadata.getSize()));
                }else {
    
                    IOUtils.copy(in, out);
                }
            } catch (IOException e) {
    
                log.error("从Minio获取文件发生IO异常", e);
            }
        }
    }

	/**
     * 从网络url下载下载flv文件（二选一-2）
     *
     * @param protocol minio协议串
     * @param response http响应
     */
    public void downloadFlv(HttpServletRequest request,
                             HttpServletResponse response,
                             @RequestParam String cId) {
    
        String flvUrl = getFlvUrl(cId);
        response.setContentType("video/x-flv");
        String[] split = StringUtils.split(flvUrl, "/");
        response.addHeader("Content-Disposition", "attachment; filename=" + split[split.length-1]);
        if (StringUtils.isNotBlank(flvUrl)) {
    
            HttpURLConnection conn = null;
            try (OutputStream out = response.getOutputStream()) {
    
                URL url = new URL(flvUrl);
                conn = (HttpURLConnection)url.openConnection();
                conn.setRequestMethod("GET");
                conn.setConnectTimeout(20 * 1000);
                Long fileLarge = (long) conn.getContentLength();
                InputStream in = conn.getInputStream();
                ddxcDownload(request, response, in, out, String.valueOf(fileLarge));
            } catch (IOException e) {
    
                logger.error("获取文件发生IO异常", e);
            } finally {
    
                Objects.requireNonNull(conn).disconnect();
            }
        }
    }

	/*********************************以下为通用断点续传代码**************************************/

    /**
     * 断点续传，用于预览视频进度条拖动
     * @param request request
     * @param response response
     * @param in minio获取的输入流
     * @param out response的输出流
     * @param wjdx 文件大小
     */
    public void ddxc(HttpServletRequest request, HttpServletResponse response, InputStream in, OutputStream out, String wjdx) {
    

        try(BufferedInputStream bis = new BufferedInputStream(in)) {
    
            long left = 0L;
            long right;
            //请求下载块大小
            long contentLength;
            // 0,从头开始的全文下载；1,从某字节开始的下载（bytes=[left]-）；2,从某字节开始到某字节结束的下载（bytes=[left]-[right]）
            int rangeSwitch = RANGE_SWITCH_0;
            long fileLength = Long.parseLong(wjdx);

            response.reset();
            response.setHeader("Accept-Ranges", BYTES);

            // 1. 客户端请求下载一个文件块，获取待下载文件块大小
            String range = request.getHeader("Range");
            if (range != null && range.trim().length() > 0 && !StringUtils.equals(range, STRING_NULL)) {
    
                response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT);
                String rangBytes = range.replaceAll(BYTES_EQUALS, StringUtils.EMPTY);
                if (rangBytes.endsWith(SPLITER)) {
    
                    // bytes=[left]-
                    rangeSwitch = RANGE_SWITCH_1;
                    left = Long.parseLong(rangBytes.substring(0, rangBytes.indexOf(SPLITER)));
                    // 客户端请求的是[left]之后的字节（包括bytes下标索引为[left]的字节）
                    contentLength = fileLength - left;
                } else {
    
                    // bytes=[left]-[right]
                    rangeSwitch = RANGE_SWITCH_2;
                    String[] rangBytesArray = rangBytes.split(SPLITER);
                    left = Long.parseLong(rangBytesArray[0]);
                    right = Long.parseLong(rangBytesArray[1]);
                    // 客户端请求的是 [left]-[right] 之间的字节
                    contentLength = right - left + 1;
                }
            } else {
    
                contentLength = fileLength;
            }

            // 2. 如果设设置了Content-Length，则客户端会自动进行多线程下载。
            // Content-Length: [文件的总大小] - [客户端请求的下载的文件块的开始字节]
            response.setHeader("Content-Length", Long.toString(contentLength));

            // 3. Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小]
            String contentRange;
            switch (rangeSwitch){
    
                case RANGE_SWITCH_1:
                    contentRange = BYTES_SPACE + left + SPLITER + (fileLength - 1) + SLASH + fileLength;
                    bis.skip(left);
                    break;
                case RANGE_SWITCH_2:
                    contentRange = range.replace(STRING_EQUALS, SPACE) + SLASH + fileLength;
                    bis.skip(left);
                    break;
                default:
                    contentRange = BYTES_SPACE + ZERO_LEFT + (fileLength - 1) + SLASH + fileLength;
            }
            response.setHeader("Content-Range", contentRange);

            // 4. 将该块文件刷出
            int n;
            long readLength = 0;
            byte[] bytes = new byte[DEFAULT_BUFFER_SIZE];
            if (rangeSwitch == RANGE_SWITCH_2) {
    
                // 针对 bytes=[left]-[right] 的请求，从[left]开始写数据
                while (readLength <= contentLength - DEFAULT_BUFFER_SIZE) {
    
                    n = bis.read(bytes);
                    readLength += n;
                    out.write(bytes, 0, n);
                }
                if (readLength <= contentLength) {
    
                    n = bis.read(bytes, 0, (int) (contentLength - readLength));
                    out.write(bytes, 0, n);
                }
            } else {
    
                while ((n = bis.read(bytes)) != -1) {
    
                    out.write(bytes, 0, n);
                }
            }
            out.flush();
        }catch (IOException ioe) {
    
            // 忽略 ClientAbortException 之类的异常，断点续传这里会抛很多EOF异常，忽略
        }catch (Exception e) {
    
            log.error("断点续传出现异常！", e);
        }
    }

附文件MediaType处理

MediaType.java

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.stream.Collectors;

import org.apache.commons.io.IOUtils;

import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Getter;
import lombok.ToString;
import lombok.experimental.Accessors;
import lombok.extern.slf4j.Slf4j;

/**
 * MediaType （资源的媒体类型）
 *
 * @version 4.0.0
 */
@Slf4j
@Getter
@ToString
@Builder(builderClassName = "Builder")
@AllArgsConstructor
@Accessors(chain = true)
public class MediaType {
    
    /**
     * 文件扩展名
     */
    private String extension;

    /**
     * 资源的媒体类型
     */
    private String mimeType;

    public static final MediaType DEF_TYPE = new Builder().extension("default").mimeType("application/octet-stream").build();

    /**
     * 获取mimeType（资源的媒体类型）
     *
     * @param extension 文件扩展名
     * @return mimeType（资源的媒体类型）
     */
    public static String getMimeType(String extension) {
    
        return Holder.types.getOrDefault(extension, DEF_TYPE).getMimeType();
    }

    /**
     * 获取mimeType（资源的媒体类型）
     *
     * @param extension 文件扩展名
     * @return mimeType（资源的媒体类型）
     */
    public static Optional<MediaType> getType(String extension) {
    
        return Optional.ofNullable(Holder.types.get(extension));
    }

    private static class Holder {
    
        private static Map<String, MediaType> types;

        private static final String WHAT = "\r";

        static {
    
            List<MediaType> list = new ArrayList<>();

            try (InputStream resourceAsStream = MediaType.class.getResourceAsStream("/mime.properties");
                 ByteArrayOutputStream bos = new ByteArrayOutputStream()) {
    
                IOUtils.copy(resourceAsStream, bos);
                String s = bos.toString(StandardCharsets.UTF_8.displayName());
                String[] stringArray;
                if (s.contains(WHAT)) {
    
                    stringArray = s.split("\r\n");
                } else {
    
                    stringArray = s.split("\n");
                }
                for (String str : stringArray) {
    
                    String[] split = str.split("=");
                    list.add(new Builder().extension(split[0]).mimeType(split[1]).build());
                }
            } catch (IOException e) {
    
                log.error("", e);
            }
            types = list.stream().collect(Collectors.toMap(MediaType::getExtension, mimeType -> mimeType));
        }
    }

}

mime.properties

IVF=video/x-ivf
a11=application/x-a11
acp=audio/x-mei-aac
ai=application/postscript
aif=audio/aiff
aifc=audio/aiff
aiff=audio/aiff
anv=application/x-anv
apk=application/vnd.android.package-archive
asa=text/asa
asf=video/x-ms-asf
asp=text/asp
asx=video/x-ms-asf
au=audio/basic
avi=video/avi
awf=application/vnd.adobe.workflow
biz=text/xml
bmp=image/bmp
bot=application/x-bot
c4t=application/x-c4t
c90=application/x-c90
cal=application/x-cals
cat=application/vnd.ms-pki.seccat
cdf=application/x-netcdf
cdr=application/x-cdr
cel=application/x-cel
cer=application/x-x509-ca-cert
cg4=application/x-g4
cgm=application/x-cgm
cit=application/x-cit
class=java/*
cml=text/xml
cmp=application/x-cmp
cmx=application/x-cmx
cot=application/x-cot
crl=application/pkix-crl
crt=application/x-x509-ca-cert
csi=application/x-csi
css=text/css
cut=application/x-cut
dbf=application/x-dbf
dbm=application/x-dbm
dbx=application/x-dbx
dcd=text/xml
dcx=application/x-dcx
der=application/x-x509-ca-cert
dgn=application/x-dgn
dib=application/x-dib
dll=application/x-msdownload
doc=application/msword
dot=application/msword
drw=application/x-drw
dtd=text/xml
dwf=application/x-dwf
dwg=application/x-dwg
dxb=application/x-dxb
dxf=application/x-dxf
edn=application/vnd.adobe.edn
emf=application/x-emf
eml=message/rfc822
ent=text/xml
epi=application/x-epi
eps=application/x-ps
etd=application/x-ebx
exe=application/x-msdownload
fax=image/fax
fdf=application/vnd.fdf
fif=application/fractals
fo=text/xml
frm=application/x-frm
g4=application/x-g4
gbr=application/x-gbr
gif=image/gif
gl2=application/x-gl2
gp4=application/x-gp4
hgl=application/x-hgl
hmr=application/x-hmr
hpg=application/x-hpgl
hpl=application/x-hpl
hqx=application/mac-binhex40
hrf=application/x-hrf
hta=application/hta
htc=text/x-component
htm=text/html
html=text/html
htt=text/webviewhtml
htx=text/html
icb=application/x-icb
ico=image/x-icon
iff=application/x-iff
ig4=application/x-g4
igs=application/x-igs
iii=application/x-iphone
img=application/x-img
ins=application/x-internet-signup
ipa=application/vnd.iphone
isp=application/x-internet-signup
java=java/*
jfif=image/jpeg
jpe=image/jpeg
jpeg=image/jpeg
jpg=image/jpeg
js=application/x-javascript
jsp=text/html
la1=audio/x-liquid-file
lar=application/x-laplayer-reg
latex=application/x-latex
lavs=audio/x-liquid-secure
lbm=application/x-lbm
lmsff=audio/x-la-lms
ls=application/x-javascript
ltr=application/x-ltr
m1v=video/x-mpeg
m2v=video/x-mpeg
m3u=audio/mpegurl
m4e=video/mpeg4
mac=application/x-mac
man=application/x-troff-man
math=text/xml
mdb=application/x-mdb
mfp=application/x-shockwave-flash
mht=message/rfc822
mhtml=message/rfc822
mi=application/x-mi
mid=audio/mid
midi=audio/mid
mil=application/x-mil
mml=text/xml
mnd=audio/x-musicnet-download
mns=audio/x-musicnet-stream
mocha=application/x-javascript
movie=video/x-sgi-movie
mp1=audio/mp1
mp2=audio/mp2
mp2v=video/mpeg
mp3=audio/mp3
m4a=audio/x-m4a
mp4=video/mp4
mpa=video/x-mpg
mpd=application/vnd.ms-project
mpe=video/x-mpeg
mpeg=video/mpg
mpg=video/mpg
mpga=audio/rn-mpeg
mpp=application/vnd.ms-project
mps=video/x-mpeg
mpt=application/vnd.ms-project
mpv=video/mpg
mpv2=video/mpeg
mpw=application/vnd.ms-project
mpx=application/vnd.ms-project
mtx=text/xml
mxp=application/x-mmxp
net=image/pnetvue
nrf=application/x-nrf
nws=message/rfc822
odc=text/x-ms-odc
out=application/x-out
p10=application/pkcs10
p12=application/x-pkcs12
p7b=application/x-pkcs7-certificates
p7c=application/pkcs7-mime
p7m=application/pkcs7-mime
p7r=application/x-pkcs7-certreqresp
p7s=application/pkcs7-signature
pc5=application/x-pc5
pci=application/x-pci
pcl=application/x-pcl
pcx=application/x-pcx
pdf=application/pdf
pdx=application/vnd.adobe.pdx
pfx=application/x-pkcs12
pgl=application/x-pgl
pic=application/x-pic
pko=application/vnd.ms-pki.pko
pl=application/x-perl
plg=text/html
pls=audio/scpls
plt=application/x-plt
png=image/png
pot=application/vnd.ms-powerpoint
ppa=application/vnd.ms-powerpoint
ppm=application/x-ppm
pps=application/vnd.ms-powerpoint
ppt=application/x-ppt
pr=application/x-pr
prf=application/pics-rules
prn=application/x-prn
prt=application/x-prt
ps=application/x-ps
ptn=application/x-ptn
pwz=application/vnd.ms-powerpoint
r3t=text/vnd.rn-realtext3d
ra=audio/vnd.rn-realaudio
ram=audio/x-pn-realaudio
ras=application/x-ras
rat=application/rat-file
rdf=text/xml
rec=application/vnd.rn-recording
red=application/x-red
rgb=application/x-rgb
rjs=application/vnd.rn-realsystem-rjs
rjt=application/vnd.rn-realsystem-rjt
rlc=application/x-rlc
rle=application/x-rle
rm=application/vnd.rn-realmedia
rmf=application/vnd.adobe.rmf
rmi=audio/mid
rmj=application/vnd.rn-realsystem-rmj
rmm=audio/x-pn-realaudio
rmp=application/vnd.rn-rn_music_package
rms=application/vnd.rn-realmedia-secure
rmvb=application/vnd.rn-realmedia-vbr
rmx=application/vnd.rn-realsystem-rmx
rnx=application/vnd.rn-realplayer
rp=image/vnd.rn-realpix
rpm=audio/x-pn-realaudio-plugin
rsml=application/vnd.rn-rsml
rt=text/vnd.rn-realtext
rtf=application/x-rtf
rv=video/vnd.rn-realvideo
sam=application/x-sam
sat=application/x-sat
sdp=application/sdp
sdw=application/x-sdw
sis=application/vnd.symbian.install
sisx=application/vnd.symbian.install
sit=application/x-stuffit
slb=application/x-slb
sld=application/x-sld
slk=drawing/x-slk
smi=application/smil
smil=application/smil
smk=application/x-smk
snd=audio/basic
sol=text/plain
sor=text/plain
spc=application/x-pkcs7-certificates
spl=application/futuresplash
spp=text/xml
ssm=application/streamingmedia
sst=application/vnd.ms-pki.certstore
stl=application/vnd.ms-pki.stl
stm=text/html
sty=application/x-sty
svg=text/xml
swf=application/x-shockwave-flash
tdf=application/x-tdf
tg4=application/x-tg4
tga=application/x-tga
tif=image/tiff
tiff=image/tiff
tld=text/xml
top=drawing/x-top
torrent=application/x-bittorrent
tsd=text/xml
txt=text/plain
uin=application/x-icq
uls=text/iuls
vcf=text/x-vcard
vda=application/x-vda
vdx=application/vnd.visio
vml=text/xml
vpg=application/x-vpeg005
vsd=application/x-vsd
vss=application/vnd.visio
vst=application/x-vst
vsw=application/vnd.visio
vsx=application/vnd.visio
vtx=application/vnd.visio
vxml=text/xml
wav=audio/wav
wax=audio/x-ms-wax
wb1=application/x-wb1
wb2=application/x-wb2
wb3=application/x-wb3
wbmp=image/vnd.wap.wbmp
wiz=application/msword
wk3=application/x-wk3
wk4=application/x-wk4
wkq=application/x-wkq
wks=application/x-wks
wm=video/x-ms-wm
wma=audio/x-ms-wma
wmd=application/x-ms-wmd
wmf=application/x-wmf
wml=text/vnd.wap.wml
wmv=video/x-ms-wmv
wmx=video/x-ms-wmx
wmz=application/x-ms-wmz
wp6=application/x-wp6
wpd=application/x-wpd
wpg=application/x-wpg
wpl=application/vnd.ms-wpl
wq1=application/x-wq1
wr1=application/x-wr1
wri=application/x-wri
wrk=application/x-wrk
ws=application/x-ws
ws2=application/x-ws
wsc=text/scriptlet
wsdl=text/xml
wvx=video/x-ms-wvx
x_b=application/x-x_b
x_t=application/x-x_t
xap=application/x-silverlight-app
xdp=application/vnd.adobe.xdp
xdr=text/xml
xfd=application/vnd.adobe.xfd
xfdf=application/vnd.adobe.xfdf
xhtml=text/html
xls=application/x-xls
xlw=application/x-xlw
xml=text/xml
xpl=audio/scpls
xq=text/xml
xql=text/xml
xquery=text/xml
xsd=text/xml
xsl=text/xml
xslt=text/xml
xwd=application/x-xwd