废话不多说，直接上代码
一、下载逻辑
public void downAppApk(HttpServletResponse response){
ClassPathResource classPathResource = new ClassPathResource("app/xxxxxx.apk");
if (!classPathResource.exists()) {
throw new BusinessException("安装包不存在");
}
String appName = URLEncoder.encode("xxxxxx","UTF-8") + ".apk";
InputStream inputStream = classPathResource.getInputStream();
OutputStream outputStream = response.getOutputStream();
response.setContentType("application/vnd.android.package-archive");
response.setCharacterEncoding("utf-8");
response.setHeader("Content-disposition", "attachment;filename=" + appName);
IOUtils.copy(inputStream,outputStream);
}二、格式对照表
比较全面的contentType的类型值
文件扩展名 Content-Type(Mime-Type)
.*（ 二进制流，不知道下载文件类型） application/octet-stream
.tif image/tiff
.asp text/asp
.asx video/x-ms-asf
.au audio/basic
.avi video/avi
.awf application/vnd.adobe.workflow
.biz text/xml
.bmp application/x-bmp
.bot application/x-bot
.cit application/x-cit
.class java/*
.csi application/x-csi
.css text/css
.dcd text/xml
.dcx application/x-dcx
.dib application/x-dib
.dll application/x-msdownload
.doc application/msword
.dot application/msword
.drw application/x-drw
.dtd text/xml
.dwf Model/vnd.dwf
.dwf application/x-dwf
.etd application/x-ebx
.exe application/x-msdownload
.gif image/gif
.gl2 application/x-gl2
.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
.ico application/x-ico
.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
.java java/*
.jfif image/jpeg
.jpe image/jpeg
.jpe application/x-jpe
.jpeg image/jpeg
.jpg image/jpeg
.jpg application/x-jpg
.js application/x-javascript
.jsp text/html
.la1 audio/x-liquid-file
.mdb application/msaccess
.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
.mp4 video/mpeg4
.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
.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
.png application/x-png
.pot application/vnd.ms-powerpoint
.ppa application/vnd.ms-powerpoint
.ppm application/x-ppm
.pps application/vnd.ms-powerpoint
.ppt 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
.ps application/postscript
.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/msword
.rtf application/x-rtf
.rv video/vnd.rn-realvideo
.sam application/x-sam
.sat application/x-sat
.sdp application/sdp
.sdw application/x-sdw
.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
.tif application/x-tif
.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/vnd.visio
.vsd application/x-vsd
.vss application/vnd.visio
.vst 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
.xdp application/vnd.adobe.xdp
.xdr text/xml
.xfd application/vnd.adobe.xfd
.xfdf application/vnd.adobe.xfdf
.xhtml text/html
.xls application/vnd.ms-excel
.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
.x_b application/x-x_b
.sis application/vnd.symbian.install
.sisx application/vnd.symbian.install
.x_t application/x-x_t
.ipa application/vnd.iphone
.apk application/vnd.android.package-archive
.xap application/x-silverlight-app