Upload files from Java client to a HTTP server

Question

I d like to upload a few files to a HTTP server  Basically what I need is some sort of a POST request to the server with a few parameters and the files  I ve seen examples of just uploading files  but didn t find how to also pass additional parameters    What s the simplest and free solution of doing this  Does anyone have any file upload examples that I could study  I ve been googling for a few hours  but  maybe it s just one of those days  couldn t find exactly what I needed  The best solution would be something that doesn t involve any third party classes or libraries

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public static String simSearchByImgURL int  catid  String imgurl  throws IOException      CloseableHttpClient httpClient   HttpClients createDefault        CloseableHttpResponse response   null      String result  null      try           HttpPost httppost   new HttpPost  http   api0 visualsearchapi com 8084 vsearchtech api v1 0 apisim search            StringBody catidBody   new StringBody catid      ContentType TEXT PLAIN           StringBody keyBody   new StringBody APPKEY   ContentType TEXT PLAIN           StringBody langBody   new StringBody LANG   ContentType TEXT PLAIN           StringBody fmtBody   new StringBody FMT   ContentType TEXT PLAIN           StringBody imgurlBody   new StringBody imgurl   ContentType TEXT PLAIN           MultipartEntityBuilder builder   MultipartEntityBuilder create            builder addPart  apikey   keyBody  addPart  catid   catidBody           addPart  lang   langBody           addPart  fmt   fmtBody           addPart  imgurl   imgurlBody           HttpEntity reqEntity    builder build            httppost setEntity reqEntity           response   httpClient execute httppost           HttpEntity resEntity   response getEntity            if  resEntity    null                  result   ConvertStreamToString resEntity getContent     UTF-8                String charset    UTF-8                String content EntityUtils toString response getEntity    charset                  System out println content                     EntityUtils consume resEntity        catch Exception e           e printStackTrace         finally           response close            httpClient close              return result

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Here is how you could do it with Java 11 s java net http package       var fileA   new File  a pdf        var fileB   new File  b pdf         var mimeMultipartData   MimeMultipartData newBuilder                withCharset StandardCharsets UTF 8               addFile  file1   fileA toPath    Files probeContentType fileA toPath                  addFile  file2   fileB toPath    Files probeContentType fileB toPath                  build         var request   HttpRequest newBuilder                header  Content-Type   mimeMultipartData getContentType                 POST mimeMultipartData getBodyPublisher                 uri URI create  http   somehost upload                 build         var httpClient   HttpClient newBuilder   build        var response   httpClient send request  BodyHandlers ofString       With the following MimeMultipartData   public class MimeMultipartData        public static class Builder            private String boundary          private Charset charset   StandardCharsets UTF 8          private List lt MimedFile gt  files   new ArrayList lt MimedFile gt             private Map lt String  String gt  texts   new LinkedHashMap lt  gt              private Builder                 this boundary   new BigInteger 128  new Random    toString                       public Builder withCharset Charset charset                this charset   charset              return this                     public Builder withBoundary String boundary                this boundary   boundary              return this                     public Builder addFile String name  Path path  String mimeType                this files add new MimedFile name  path  mimeType                return this                     public Builder addText String name  String text                texts put name  text               return this                     public MimeMultipartData build   throws IOException               MimeMultipartData mimeMultipartData   new MimeMultipartData                mimeMultipartData boundary   boundary               var newline     r n  getBytes charset               var byteArrayOutputStream   new ByteArrayOutputStream                for  var f   files                    byteArrayOutputStream write   --    boundary  getBytes charset                     byteArrayOutputStream write newline                   byteArrayOutputStream write   Content-Disposition  form-data  name       f name        filename       f path getFileName           getBytes charset                    byteArrayOutputStream write newline                   byteArrayOutputStream write   Content-Type      f mimeType  getBytes charset                    byteArrayOutputStream write newline                   byteArrayOutputStream write newline                   byteArrayOutputStream write Files readAllBytes f path                    byteArrayOutputStream write newline                             for  var entry  texts entrySet                      byteArrayOutputStream write   --    boundary  getBytes charset                    byteArrayOutputStream write newline                   byteArrayOutputStream write   Content-Disposition  form-data  name       entry getKey           getBytes charset                    byteArrayOutputStream write newline                   byteArrayOutputStream write newline                   byteArrayOutputStream write entry getValue   getBytes charset                    byteArrayOutputStream write newline                             byteArrayOutputStream write   --    boundary    --   getBytes charset                 mimeMultipartData bodyPublisher   BodyPublishers ofByteArray byteArrayOutputStream toByteArray                 return mimeMultipartData                     public class MimedFile                public final String name              public final Path path              public final String mimeType               public MimedFile String name  Path path  String mimeType                    this name   name                  this path   path                  this mimeType   mimeType                                     private String boundary      private BodyPublisher bodyPublisher       private MimeMultipartData                public static Builder newBuilder             return new Builder               public BodyPublisher getBodyPublisher   throws IOException           return bodyPublisher             public String getContentType             return  multipart form-data  boundary     boundary

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It could depend on your framework   for each of them could exist an easier solution    But to answer your question  there are a lot of external libraries for this functionality  Look here how to use apache commons fileupload

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protected void doPost HttpServletRequest request          HttpServletResponse response  throws ServletException  IOException        boolean isMultipart   ServletFileUpload isMultipartContent request        if   isMultipart            return             DiskFileItemFactory factory   new DiskFileItemFactory         factory setSizeThreshold MAX MEMORY SIZE        factory setRepository new File System getProperty  java io tmpdir           String uploadFolder   getServletContext   getRealPath                   File separator   DATA DIRECTORY   DATA DIRECTORY is directory where you upload this file on the server      ServletFileUpload upload   new ServletFileUpload factory        upload setSizeMax MAX REQUEST SIZE    MAX REQUEST SIZE is the size which size you prefer   And use  lt form  enctype  multipart form-data  gt  and use  lt input type  file  gt  in the html

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Here is how you would do it with Apache HttpClient  this solution is for those who don t mind using a 3rd party library        HttpEntity entity   MultipartEntityBuilder create                           addPart  file   new FileBody file                           build         HttpPost request   new HttpPost url       request setEntity entity        HttpClient client   HttpClientBuilder create   build        HttpResponse response   client execute request

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click link get example  file upload clint java with apache HttpComponents   http   hc apache org httpcomponents-client-ga httpmime examples org apache http examples entity mime ClientMultipartFormPost java  and library downalod link  https   hc apache org downloads cgi  use 4 5 3 zip it s working fine in my code  and my working code    import java io File  import org apache http HttpEntity  import org apache http client methods CloseableHttpResponse  import org apache http client methods HttpPost  import org apache http entity ContentType  import org apache http entity mime MultipartEntityBuilder  import org apache http entity mime content FileBody  import org apache http entity mime content StringBody  import org apache http impl client CloseableHttpClient  import org apache http impl client HttpClients  import org apache http util EntityUtils   public class ClientMultipartFormPost         public static void main String   args  throws Exception              CloseableHttpClient httpclient   HttpClients createDefault              try                HttpPost httppost   new HttpPost  http   localhost 8080 MyWebSite1 UploadDownloadFileServlet                  FileBody bin   new FileBody new File  E   meter jpg                  StringBody comment   new StringBody  A binary file of some kind   ContentType TEXT PLAIN                 HttpEntity reqEntity   MultipartEntityBuilder create                    addPart  bin   bin                   addPart  comment   comment                   build                   httppost setEntity reqEntity                 System out println  executing request     httppost getRequestLine                  CloseableHttpResponse response   httpclient execute httppost              try                   System out println  ----------------------------------------                    System out println response getStatusLine                     HttpEntity resEntity   response getEntity                    if  resEntity    null                         System out println  Response content length         resEntity getContentLength                                     EntityUtils consume resEntity                  finally                    response close                           finally             httpclient close

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You d normally use java net URLConnection to fire HTTP requests  You d also normally use multipart form-data encoding for mixed POST content  binary and character data   Click the link  it contains information and an example how to compose a multipart form-data request body  The specification is in more detail described in RFC2388   Here s a kickoff example   String url    http   example com upload   String charset    UTF-8   String param    value   File textFile   new File   path to file txt    File binaryFile   new File   path to file bin    String boundary   Long toHexString System currentTimeMillis        Just generate some unique random value  String CRLF     r n      Line separator required by multipart form-data   URLConnection connection   new URL url  openConnection    connection setDoOutput true   connection setRequestProperty  Content-Type    multipart form-data  boundary     boundary    try       OutputStream output   connection getOutputStream        PrintWriter writer   new PrintWriter new OutputStreamWriter output  charset   true              Send normal param      writer append  --    boundary  append CRLF       writer append  Content-Disposition  form-data  name   param     append CRLF       writer append  Content-Type  text plain  charset     charset  append CRLF       writer append CRLF  append param  append CRLF  flush            Send text file      writer append  --    boundary  append CRLF       writer append  Content-Disposition  form-data  name   textFile    filename       textFile getName           append CRLF       writer append  Content-Type  text plain  charset     charset  append CRLF      Text file itself must be saved in this charset      writer append CRLF  flush        Files copy textFile toPath    output       output flush       Important before continuing with writer      writer append CRLF  flush       CRLF is important  It indicates end of boundary          Send binary file      writer append  --    boundary  append CRLF       writer append  Content-Disposition  form-data  name   binaryFile    filename       binaryFile getName           append CRLF       writer append  Content-Type      URLConnection guessContentTypeFromName binaryFile getName     append CRLF       writer append  Content-Transfer-Encoding  binary   append CRLF       writer append CRLF  flush        Files copy binaryFile toPath    output       output flush       Important before continuing with writer      writer append CRLF  flush       CRLF is important  It indicates end of boundary          End of multipart form-data      writer append  --    boundary    --   append CRLF  flush          Request is lazily fired whenever you need to obtain information about response  int responseCode     HttpURLConnection  connection  getResponseCode    System out println responseCode      Should be 200   This code is less verbose when you use a 3rd party library like Apache Commons HttpComponents Client   The Apache Commons FileUpload as some incorrectly suggest here is only of interest in the server side  You can t use and don t need it at the client side   See also   Using java net URLConnection to fire and handle HTTP requests

[java] Upload files from Java client to a HTTP server

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