Ultra detailed file upload and download (Spring Boot)

Language 2023-05-05 00:59:37 views: null

Ultra-detailed file uploads and downloads

Preface Ⅰ: The difference between @RequestParam and @RequestPart

@RequestPart

  • @RequestPartThis annotation is used on multipart/form-datathe form submit request method.
  • The supported request method methods MultipartFilebelong to the Spring MultipartResolverclass. This request is http协议transmitted via

@RequestParam

  • @RequestParamsupport application/json, as well as support multipart/form-datarequests

code demo

  • Test 1: Use @RequestPart to receive json data

    Conclusion : @RequestPartcan be converted jsonDatatojson数据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();
}
    parameter name parameter value Parameter Type
    file1 a file file
    person {"name":"cvzhanshi","age":23} application/json

    Test result: can use object to receive json

    insert image description here

  • Test 2: Use @RequestParam to receive json data

    Conclusion : @RequestParamfor jsonDataonly used tojson数据 receiveString字符串

    /**
     * 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]

Error description: only receive and parse string type

difference (summary)

  • Only values ​​that can be received when the request is, canmultipart/form-data receive complex request fields (like )@RequestParamString类型name-value@RequestPartjson、xml
  • @RequestParamDepend Converter or PropertyEditoron data analysis, @RequestPartreference 'Content-Type' header, depend HttpMessageConverterson data analysis
  • When Content-Type: multipart/form-data is specified in the request header, the passed json parameter, @RequestPart annotation can be received by object, @RequestParam can only be received by string
  • @RequestParam is suitable for request fields of name-valueString type, and @RequestPart is suitable for complex request fields (like JSON, XML); the biggest difference between them is that when the request parameter type of the request method is no longer of String type

Preface Ⅱ: ​​The difference between getParameter() and getPart()

code testing

/**
     * 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 "";
}

pass parameters

key value type
name cvzhanshi text
age 18 text
file1 New text document.txt file
file2 Beauty.jpg file

Debug analysis :

  • request : You can see that the request has two Parameter and two Part parameters

    insert image description here

  • Parameter and Part : the value obtained by request.getParameter and the value obtained by request.getPart

    insert image description here

    It turns out that: using request.getParameter() to get the file type parameter is empty, and using request.getPart() to get the non-file type is empty

  • ParameterNames and Parts : getParameterNames() and getParts() get parameter names

    insert image description here

    insert image description here

    Result: use request.getParameterNames() to get only non-file type parameter names, use request.getParts() to get all parameter names

in conclusion

  • Part can get the parameter names of all request parameters, while Parameter can only get the parameter names of non-file types
  • Part cannot obtain the parameter value of a non-file type parameter, and Part obtains a binary input stream
  • Parameter can only get non-file type parameter values
  • It is very convenient to use Part to get files, you can get the file size and file type

Ⅰ: File upload

① form-data type upload

The form-data type is a commonly used form submission, and there are two ways to receive files from the front end

  • Receive the byte stream through the Part mentioned above, namely @RequestPart annotation and request.getParts()
  • Receive files from the front end through the MultipartFile class

Explanation: The two methods are similar

Front-end interface submission

insert image description here

Backend code (interface) for uploading files

/**
     * 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.";
    }
}

test

insert image description here

② Binary type upload

binary This type refers to some binary file types, such as application/pdf, which specifies the MIME type of a specific binary file. Just like for text file types if there is no specific subtype

(subtype), use text/plain. Similarly, binary files do not have a specific or known subtype, i.e. use application/octet-stream, which is the default for application files.

For application/octet-stream, only binary can be submitted, and only one binary can be submitted. If a file is submitted, only one file can be submitted. There can only be one receiving parameter in the background, and it can only be a stream

(or byte array)

Front-end interface submission

insert image description here

Backend code (interface) for uploading files

/**
     * 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";
}

test

insert image description here

Description: part is more convenient to use, it accepts byte stream, and it is more convenient to read file type, file name and file size

③ Configuration instructions

If you do not customize the configuration, he will upload the default size of 1M\

The SpringBoot project is configured through the configuration file

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: File download

① Supplementary explanation

Content-Disposition

  • In a regular HTTP response, Content-Dispositionthe response header indicates in what form the content of the response should be displayed, whether it is inline (that is, a web page or part of a page), or downloaded and saved locally as an attachment
  • In the response message body of multipart/form-data type, Content-Dispositionthe message header can be used in the subpart of the multipart message body to give relevant information of its corresponding field. Each subsection is separated by the delimiterContent-Type defined in . It has no practical meaning when used in the message body itself.

Grammar :

  • As a message header in the message body : In the HTTP scenario, the first parameter is either inline(the default value, indicating that the message body in the reply will be displayed as a part of the page or the entire page), or ( attachmentmeaning the message body should be Download locally; most browsers will present a "Save As" dialog, pre filename- filling the value of with the downloaded filename, if it exists).

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

  • As a header in a multipart body : in an HTTP scenario. The first parameter is always fixed form-data; additional parameters are case-insensitive and have parameter values. The parameter name and parameter value are '='connected with an equal sign ( ), and the parameter value is enclosed in double quotation marks. Parameters are separated by semicolons ( ';').

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

The String parameter and corresponding type of response.setContentType()

file extension Content-Type(Mime-Type) file extension Content-Type(Mime-Type)
.* (binary stream, unaware of download file type) 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/so .asf video/x-ms-asf
.asp text/asp .asx video/x-ms-asf
.au audio/basic .avi I saw
.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
.The 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
.the application/x-x509-ca-cert .with application/x-dgn
.back application/x-dib .dll application/x-msdownload
.doc application/msword .dot application/msword
.through application/x-drw .dtd text/xml
.growth Model/vnd.growth .growth 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 Download local resources

download code

/**
     * 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);
        }
    }
}

Test link: http://localhost:8888/download?fileName=background.jpg

​ Or http://localhost:8888/download?isOnLine=true&fileName=background.jpg

③ Download network resources

code demo

Explanation: You must first obtain the correct url to obtain the desired resource

/**
     * 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();
}

Test link: http://localhost:8888/downLoadMusic

Reference Article 1

Reference Article 2

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Origin blog.csdn.net/qq_45408390/article/details/127253216
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