超详细的文件上传和下载(Spring Boot)

超详细的文件上传和下载

前言Ⅰ：@RequestParam和@RequestPart的区别

@RequestPart

• @RequestPart这个注解用在multipart/form-data表单提交请求的方法上。
• 支持的请求方法的方式MultipartFile，属于Spring的MultipartResolver类。这个请求是通过http协议传输的

@RequestParam

• @RequestParam支持application/json，也同样支持multipart/form-data请求

代码演示

• 测试一：使用@RequestPart接收json数据

  结论：@RequestPart可以将jsonData的json数据转换为Person对象

  /**
       * 测试 RequestParam 和 RequestPart区别2
       * @param person
       * @param file1
       * @return
       * @throws IOException
       * @throws ServletException
       */
  @RequestMapping(value = "/upload3",method = RequestMethod.POST)
  @ResponseBody
  public String readFile1(@RequestPart("person") Person person , @RequestPart("file1") MultipartFile file1)  {
      StringBuilder sb = new StringBuilder();
      sb.append(file1.getOriginalFilename()).append(";;;");
      return person.toString() + ":::" + sb.toString();
  }
  

  参数名	参数值	参数类型
  file1	一个文件	file
  person	{“name”:“cvzhanshi”,“age”:23}	application/json

  测试结果：能够用对象去接收json

  

• 测试二：使用@RequestParam接收json数据

  结论：@RequestParam对于jsonData的json数据只能用String字符串来接收

  /**
       * 测试 RequestParam 和 RequestPart区别2
       * @param person
       * @param file1
       * @return
       * @throws IOException
       * @throws ServletException
       */
  @RequestMapping(value = "/upload3",method = RequestMethod.POST)
  @ResponseBody
  public String readFile1(@RequestParam("person") Person person , @RequestPart("file1") MultipartFile file1)  {
      StringBuilder sb = new StringBuilder();
      sb.append(file1.getOriginalFilename()).append(";;;");
      return person.toString() + ":::" + sb.toString();
  }
  

​ 测试结果：报错 2022-10-08 10:19:48.434 WARN 3440 — [nio-8888-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.method.annotation.MethodArgumentConversionNotSupportedException: Failed to convert value of type ‘java.lang.String’ to required type ‘cn.cvzhanshi.test.entity.Person’; nested exception is java.lang.IllegalStateException: Cannot convert value of type ‘java.lang.String’ to required type ‘cn.cvzhanshi.test.entity.Person’: no matching editors or conversion strategy found]

报错说明：只能接收解析String类型的

区别(总结)

• 当请求为multipart/form-data时，@RequestParam只能接收String类型的name-value值，@RequestPart可以接收复杂的请求域（像json、xml）
• @RequestParam 依赖Converter or PropertyEditor进行数据解析， @RequestPart参考'Content-Type' header，依赖HttpMessageConverters进行数据解析
• 当请求头中指定Content-Type:multipart/form-data时，传递的json参数，@RequestPart注解可以用对象来接收，@RequestParam只能用字符串接收
• @RequestParam适用于name-valueString类型的请求域，@RequestPart适用于复杂的请求域（像JSON，XML）；他们最大的不同是，当请求方法的请求参数类型不再是String类型的时候

前言Ⅱ：getParameter() 和 getPart() 区别

代码测试

/**
     * 测试 RequestParam 和 RequestPart区别1
     * @param request
     * @param name
     * @param file1
     * @return
     * @throws IOException
     * @throws ServletException
     */
@RequestMapping(value = "/upload1",method = RequestMethod.POST)
@ResponseBody
public String readFile(HttpServletRequest request,@RequestParam("name") String name ,@RequestPart("file1") MultipartFile file1) throws IOException, ServletException {

    String ageParameter = request.getParameter("age");
    Part agePart = request.getPart("age");

    String file2Parameter = request.getParameter("file2");
    Part file2Part = request.getPart("file2");

    Enumeration<String> parameterNames = request.getParameterNames();
    Collection<Part> parts = request.getParts();
    return "";
}

传递参数

key	value	type
name	cvzhanshi	text
age	18	text
file1	新建文本文档.txt	file
file2	美女.jpg	file

DeBug分析：

• request：可以看到request有两个 Parameter 和 两个 Part 参数

  

• Parameter和Part：request.getParameter获得的值以及request.getPart获得的值

  

  结果发现：使用 request.getParameter() 获取文件类型参数为空，使用 request.getPart() 获取非文件类型为空

• ParameterNames和Parts：getParameterNames()和getParts()获取参数名

  

  

  结果：使用 request.getParameterNames() 只能获取非文件类型的参数名, 使用 request.getParts() 可以获取全部参数名

结论

• Part 能获取所有的请求参数的参数名，而 Parameter 只能获取非文件类型的参数名
• Part 不能获得非文件类型参数的参数值，Part获得二进制的输入流
• Parameter 只能获得非文件类型参数值
• 使用 Part 获取文件很方便，可以获取文件大小文件类型

Ⅰ：文件上传

① form-data 类型上传

form-data 类型即常用的表单提交，可以通过两种方式接收前端传过来的文件

• 通过上述讲的Part 接收字节流，即@RequestPart注解以及request.getParts()
• 通过MultipartFile类来接收前端传过来的文件

说明：两种方法差不多

前端接口提交

上传文件的后端代码（接口）

/**
     * form-data 类型(前端表单上传)
     * @param request
     * @param name
     * @param file3
     * @param photo
     * @return
     * @throws IOException
     * @throws ServletException
     */
@RequestMapping(value = "/upload", method = RequestMethod.POST)
@ResponseBody
public String readFile(HttpServletRequest request,
                       @RequestParam("name") String name,
                       @RequestPart("file1") MultipartFile file3,
                       @RequestPart("photo") MultipartFile photo
                      ) throws IOException, ServletException {



    System.out.println(name);
    /*
            第一种 ： 使用 MultipartFile 封装好的 transferTo() 方法保存文件
            photo.transferTo(new File(path + photo.getOriginalFilename()));
         */
    /*
            第二种 ：  使用 MultipartFile 字节流保存文件
            fileUtil(file3, String.valueOf(path));
         */


    /*第三种 ：用 Part 接收文件字节流
            Part file2 = request.getPart("file2");
            file2.write(path + file2.getSubmittedFileName());
            request.getParts() 获取的是全部参数（name,age,file1,file2），包括文件参数和非文件参数
		 */
    for (Part part : request.getParts()) {
        // 获取文件类型
        part.getContentType();
        // 获取文件大小
        part.getSize();
        // 获取文件名
        part.getSubmittedFileName();
        // 获取参数名 （name,age,file1,file2）
        part.getName();
        if(part.getContentType()!=null){
            part.write(path + part.getSubmittedFileName());
        }else{
            // 可以获取文本参数值,文本参数 part.getContentType()为 null
            System.out.println(request.getParameter(part.getName()));
        }
    }
    return "success";
}


/**
     * 字节流上传文件工具方法
     * @param file
     * @param path
     * @return
     */
public String fileUtil(MultipartFile file, String path) {
    if (!file.isEmpty()) {
        try {
            // 转化成字节流
            byte[] bytes = file.getBytes();
            bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(
                new File(path + file.getOriginalFilename())));
            // 写出
            bufferedOutputStream.write(bytes);
            // 关闭资源
            bufferedOutputStream.close();
            return file.getOriginalFilename() + " 上传成功";
        } catch (Exception e) {
            return file.getOriginalFilename() + " failed to upload ---> " + e;
        }
    } else {
        return file.getOriginalFilename() + "You failed to upload file was empty.";
    }
}

测试

② binary 类型上传

binary 这一类型，指的就是一些二进制文件类型，如application/pdf，指定了特定二进制文件的MIME类型。就像对于text文件类型若没有特定的子类型

（subtype），就使用 text/plain。类似的，二进制文件没有特定或已知的 subtype，即使用 application/octet-stream，这是应用程序文件的默认值。

对于application/octet-stream，只能提交二进制，而且只能提交一个二进制，如果提交文件的话，只能提交一个文件，后台接收参数只能有一个，而且只能是流

（或者字节数组）

前端接口提交

上传文件的后端代码（接口）

/**
     * binary 类型上传
     * @param request
     * @return
     * @throws IOException
     */
@RequestMapping(value = "/upload2",method = RequestMethod.POST)
public String upload2(HttpServletRequest request) throws IOException {
    ServletInputStream inputStream = null;
    FileOutputStream fileOutputStream = null;
    try {
        // 获取上传的文件流
        inputStream = request.getInputStream();
        // 定义输出流 上传到哪里
        fileOutputStream = new FileOutputStream(new File(path + "a.pdf"));

        int len;
        byte[] bytes = new byte[1024];
        while((len = inputStream.read(bytes))!=-1){
            fileOutputStream.write(bytes,0,len);
        }
    } catch (IOException e) {
        e.printStackTrace();
        return "上传失败";
    } finally {
        // 关闭资源
        if(fileOutputStream!=null){
            fileOutputStream.close();
        }
        if(inputStream!=null){
            inputStream.close();
        }
    }
    return "上传成功";
}

测试

说明：part 使用起来比较方便，接受的就是字节流，读取文件类型，文件名，文件大小也比较方便

③ 配置说明

如果不自定义配置的话，他会默认上传大小1M\

SpringBoot项目的话通过配置文件配置

server:
  port: 8888
spring:
  servlet:
    multipart:
      max-file-size: 10MB   # 最大上传大小
      max-request-size: 100MB   # 单文件最大上传大小 

Ⅱ：文件下载

① 补充说明

Content-Disposition

• 在常规的 HTTP 应答中，Content-Disposition 响应头指示回复的内容该以何种形式展示，是以内联的形式（即网页或者页面的一部分），还是以附件的形式下载并保存到本地
• 在 multipart/form-data 类型的应答消息体中，Content-Disposition 消息头可以被用在 multipart 消息体的子部分中，用来给出其对应字段的相关信息。各个子部分由在Content-Type 中定义的分隔符分隔。用在消息体自身则无实际意义。

语法：

• 作为消息主体中的消息头：在 HTTP 场景中，第一个参数或者是 inline（默认值，表示回复中的消息体会以页面的一部分或者整个页面的形式展示），或者是 attachment（意味着消息体应该被下载到本地；大多数浏览器会呈现一个“保存为”的对话框，将 filename 的值预填为下载后的文件名，假如它存在的话）。

  Content-Disposition: inline
  Content-Disposition: attachment
  Content-Disposition: attachment; filename="filename.jpg"
  

• 作为 multipart body 中的消息头：在 HTTP 场景中。第一个参数总是固定不变的 form-data；附加的参数不区分大小写，并且拥有参数值，参数名与参数值用等号 ('=') 连接，参数值用双引号括起来。参数之间用分号 (';') 分隔。

  Content-Disposition: form-data
  Content-Disposition: form-data; name="fieldName"
  Content-Disposition: form-data; name="fieldName"; filename="filename.jpg"
  

response.setContentType()的String参数及对应类型

文件扩展名	Content-Type(Mime-Type)	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
.001	application/x-001	.301	application/x-301
.323	text/h323	.906	application/x-906
.907	drawing/907	.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
.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	application/x-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	Model/vnd.dwf	.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	.eps	application/postscript
.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	.	application/x-
.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	.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
.isp	application/x-internet-signup	.IVF	video/x-ivf
.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
.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/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

② 下载本地资源

下载代码

/**
     * 下载本地资源
     * @param fileName  下载的文件名
     * @param response  响应头
     * @param isOnLine  是否默认下载  true浏览器中打开
     * @throws IOException
     */
@GetMapping("/download")
public void download(String fileName, HttpServletResponse response, boolean isOnLine) throws IOException {
    // 路径可以指定当前项目相对路径
    File file = new File(path + fileName);
    if (file.exists()) {
        // 把文件转化成流
        FileInputStream fileInputStream = new FileInputStream(file);
        ServletOutputStream outputStream = response.getOutputStream();
        // 是否立即下载
        if(!isOnLine){
            response.setContentType("application/octet-stream");
            // 如果文件名为中文需要设置编码
            response.setHeader("Content-Disposition", "attachment;fileName=" + URLEncoder.encode("背景.jpg", "utf8"));
        }
        byte[] bytes = new byte[1024];
        int len;
        // 把文件流写入响应头
        while ((len = fileInputStream.read(bytes)) != -1) {
            outputStream.write(bytes, 0, len);
        }
    }
}

测试链接：http://localhost:8888/download?fileName=背景.jpg

​ 或者http://localhost:8888/download?isOnLine=true&fileName=背景.jpg

③ 下载网络资源

代码演示

说明：首先要获取到正确的url才能获取到想要的资源

/**
     * 下载网络资源
     * @param response
     * @throws IOException
     */
@RequestMapping("/downLoadMusic")
public void downloadNetworkFile(HttpServletResponse response) throws IOException {
    // 创建url对象
    URL url = new URL("https://m701.music.126.net/20221009103058/70acd1fa2256e82ae0a90f833aec1072/jdyyaac/obj/w5rDlsOJwrLDjj7CmsOj/18195365565/53a1/ad15/9e1c/1b3457995065a152f56f61c38eda1914.m4a");
    // 建立连接
    URLConnection urlConnection = url.openConnection();
    // 获取到输入流
    InputStream inputStream = urlConnection.getInputStream();
    // 获取到响应头的输出流
    ServletOutputStream outputStream = response.getOutputStream();
    // 设置响应头
    response.setContentType("application/octet-stream");
    response.setHeader("Content-Disposition","attachment;fileName=" + URLEncoder.encode("爱似水仙.m4a", "utf8"));
    int len;
    // 通过字节流下载下来
    byte[] bytes = new byte[1024];
    while ((len = inputStream.read(bytes)) != -1){
        outputStream.write(bytes,0, len);
    }
    // 关闭资源
    inputStream.close();
    outputStream.close();
}

测试链接：http://localhost:8888/downLoadMusic

参考文章1

参考文章2