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