Getting A File s Mime Type In Java

Question

I was just wondering how most people fetch a mime type from a file in Java   So far I ve tried two utils  JMimeMagic  amp  Mime-Util     The first gave me memory exceptions  the second doesn t close its streams off properly   I was just wondering if anyone else had a method library that they used and worked correctly

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To chip in with my 5 cents   TL DR  I use MimetypesFileTypeMap and add any mime that is not there and I specifically need it  into mime types file   And now  the long read   First of all  MIME types list is huge  see here  https   www iana org assignments media-types media-types xhtml  I like to use standard facilities provided by JDK first  and if that doesn t work  I ll go and look for something else   Determine file type from file extension  Since 1 6  Java has MimetypesFileTypeMap  as pointed in one of the answers above  and it is the simplest way to determine mime type   new MimetypesFileTypeMap   getContentType  fileName      In its vanilla implementation this does not do much  i e  it works for  html but it doesn t for  png   It is  however  super simple to add any content type you may need    Create file named  mime types  in META-INF folder in your project Add a line for every mime type you need and default implementation doesn t provide  there are hundreds of mime types and list grows as time goes by     Example entries for png and js files would be   image png png PNG application javascript js   For mime types file format  see more details here  https   docs oracle com javase 7 docs api javax activation MimetypesFileTypeMap html  Determine file type from file content  Since 1 7  Java has java nio file spi FileTypeDetector  which defines a standard API for determining a file type in implementation specific way   To fetch mime type for a file  you would simply use Files and do this in your code   Files probeContentType Paths get  either file name or full path goes here       The API definition provides for facilities that support either for determining file mime type from file name or from file content  magic bytes   That is why probeContentType   method throws IOException  in case an implementation of this API uses Path provided to it to actually try to open the file associated with it   Again  vanilla implementation of this  the one that comes with JDK  leaves a lot to be desired   In some ideal world in a galaxy far  far away  all these libraries which try to solve this file-to-mime-type problem would simply implement java nio file spi FileTypeDetector  you would drop in the preferred implementing library s jar file into your classpath and that would be it   In the real world  the one where you need TL DR section  you should find the library with most stars next to it s name and use it  For this particular case  I don t need one  yet

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After trying various other libraries I settled with mime-util    lt groupId gt eu medsea mimeutil lt  groupId gt         lt artifactId gt mime-util lt  artifactId gt         lt version gt 2 1 3 lt  version gt   lt  dependency gt   File file   new File  D  test tif    MimeUtil registerMimeDetector  eu medsea mimeutil detector MagicMimeMimeDetector    Collection lt   gt  mimeTypes   MimeUtil getMimeTypes file   System out println mimeTypes

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I was just wondering how most people fetch a mime type from a file in Java     I ve published my SimpleMagic Java package which allows content-type  mime-type  determination from files and byte arrays  It is designed to read and run the Unix file 1  command magic files that are a part of most  Unix OS configurations   I tried Apache Tika but it is huge with tons of dependencies  URLConnection doesn t use the bytes of the files  and MimetypesFileTypeMap also just looks at files names   With SimpleMagic you can do something like      create a magic utility using the internal magic file ContentInfoUtil util   new ContentInfoUtil       if you want to use a different config file s   you can load them by hand     ContentInfoUtil util   new ContentInfoUtil   etc magic        ContentInfo info   util findMatch   tmp upload tmp       or ContentInfo info   util findMatch inputStream      or ContentInfo info   util findMatch contentByteArray       null if no match if  info    null       String mimeType   info getMimeType

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If you are stuck with java 5-6 then this utility class from servoy open source product   You only need this function   public static String getContentType byte   data  String name    It probes the first bytes of the content and returns the content types based on that content and not by file extension

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File file   new File PropertiesReader FILE PATH   MimetypesFileTypeMap fileTypeMap   new MimetypesFileTypeMap    String mimeType   fileTypeMap getContentType file   URLConnection uconnection   file toURL   openConnection    mimeType   uconnection getContentType

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From roseindia   FileNameMap fileNameMap   URLConnection getFileNameMap    String mimeType   fileNameMap getContentTypeFor  alert gif

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If you are working with a Servlet and if the servlet context is available to you  you can use    getServletContext   getMimeType  fileName

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With Apache Tika you need only three lines of code   File file   new File   path to file    Tika tika   new Tika    System out println tika detect file      If you have a groovy console  just paste and run this code to play with it    Grab  org apache tika tika-core 1 14   import org apache tika Tika   def tika   new Tika   def file   new File   path to file   println tika detect file    Keep in mind that its APIs are rich  it can parse  anything   As of tika-core 1 14  you have   String  detect byte   prefix  String  detect byte   prefix  String name  String  detect File file  String  detect InputStream stream  String  detect InputStream stream  Metadata metadata  String  detect InputStream stream  String name  String  detect Path path  String  detect String name  String  detect URL url    See the apidocs for more information

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Unfortunately   mimeType   file toURL   openConnection   getContentType      does not work  since this use of URL leaves a file locked  so that  for example  it is undeletable   However  you have this   mimeType  URLConnection guessContentTypeFromName file getName       and also the following  which has the advantage of going beyond mere use of file extension  and takes  a peek at content  InputStream is   new BufferedInputStream new FileInputStream file    mimeType   URLConnection guessContentTypeFromStream is         close stream   However  as suggested by the comment above  the built-in table of mime-types is quite limited  not including  for example  MSWord and PDF  So  if you want to generalize  you ll need to go beyond the built-in libraries  using  e g   Mime-Util  which is a great library  using both file extension and content

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Simple and Best option retrieve the content mime type from the file location  Use this imports import java nio file Files  import java nio file Path   Code String type   Files probeContentType Path of imagePath

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in spring MultipartFile file      org springframework web multipart MultipartFile   file getContentType

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Because there s so many answers linking to libraries  or non-portable code  I thought I d share an alternative way by simply checking the magic bytes of the stream or file that you want to know the type of  as I ve shown here   https   stackoverflow com a 65667558 3225638 It uses native java  but requires you to define in the enum the types you would want to handle detect beforehand  but you d only have to do it once

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Apache Tika offers in tika-core a mime type detection based based on magic markers in the stream prefix  tika-core does not fetch other dependencies  which makes it as lightweight as the currently unmaintained Mime Type Detection Utility  Simple code example  Java 7   using the variables theInputStream and theFileName try  InputStream is   theInputStream          BufferedInputStream bis   new BufferedInputStream is          AutoDetectParser parser   new AutoDetectParser        Detector detector   parser getDetector        Metadata md   new Metadata        md add Metadata RESOURCE NAME KEY  theFileName       MediaType mediaType   detector detect bis  md       return mediaType toString       Please note that MediaType detect      cannot be used directly  TIKA-1120   More hints are provided at https   tika apache org 1 24 detection html

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This is the simplest way I found for doing this   byte   byteArray       InputStream is   new BufferedInputStream new ByteArrayInputStream byteArray    String mimeType   URLConnection guessContentTypeFromStream is

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If you re an Android developer  you can use a utility class android webkit MimeTypeMap which maps MIME-types to file extensions and vice versa   Following code snippet may help you   private static String getMimeType String fileUrl        String extension   MimeTypeMap getFileExtensionFromUrl fileUrl       return MimeTypeMap getSingleton   getMimeTypeFromExtension extension

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It is better to use two layer validation for files upload    First you can check for the mimeType and validate it    Second you should look to convert the first 4 bytes of your file to hexadecimal and then compare it with the magic numbers  Then it will be a really secure way to check for file validations

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Apache Tika    lt  -- https   mvnrepository com artifact org apache tika tika-parsers -- gt   lt dependency gt       lt groupId gt org apache tika lt  groupId gt       lt artifactId gt tika-parsers lt  artifactId gt       lt version gt 1 24 lt  version gt   lt  dependency gt     and Two line of code   Tika tika new Tika    tika detect inputStream     Screenshot below

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I did it with following code    import java io BufferedReader  import java io InputStream  import java io InputStreamReader  import java net HttpURLConnection  import java net URL   public class MimeFileType        public static void main String args              try              URL url   new URL   https   www url com pdf                 HttpURLConnection connection    HttpURLConnection  url openConnection                connection setRequestMethod  GET                connection setDoOutput true               InputStream content    InputStream connection getInputStream                connection getHeaderField  Content-Type                 System out println  Content-Type    connection getHeaderField  Content-Type                  BufferedReader in   new BufferedReader  new InputStreamReader content              catch  Exception e

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The JAF API is part of JDK 6  Look at javax activation package   Most interesting classes are javax activation MimeType - an actual MIME type holder - and javax activation MimetypesFileTypeMap - class whose instance can resolve MIME type as String for a file   String fileName     path to file   MimetypesFileTypeMap mimeTypesMap   new MimetypesFileTypeMap        only by file name String mimeType   mimeTypesMap getContentType fileName       or by actual File instance File file   new File fileName   mimeType   mimeTypesMap getContentType file

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if you work on linux OS  there is a command line file --mimetype    String mimetype file         1  run cmd    Object cmd Runtime getRuntime   exec  file --mime-type   file         2 get output of cmd   then        3  parse mimetype     if output  return output split      1  trim          return         Then  mimetype   home nyapp war        application zip   mimetype   var www ggg au mp3        audio mp3

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I tried several ways to do it  including the first ones said by  Joshua Fox  But some don t recognize frequent mimetypes like for PDF files  and other could not be trustable with fake files  I tried with a RAR file with extension changed to TIF   The solution I found  as also is said by  Joshua Fox in a superficial way  is to use MimeUtil2  like this   MimeUtil2 mimeUtil   new MimeUtil2    mimeUtil registerMimeDetector  eu medsea mimeutil detector MagicMimeMimeDetector    String mimeType   MimeUtil2 getMostSpecificMimeType mimeUtil getMimeTypes file   toString

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public String getFileContentType String fileName        String fileType    Undetermined       final File file   new File fileName       try               fileType   Files probeContentType file toPath               catch  IOException ioException                System out println                   ERROR  Unable to determine file type for     fileName                             due to exception     ioException             return fileType

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You can do it with just one line   MimetypesFileTypeMap   getContentType new File  filename ext     Look the complete test code  Java 7    import java io File  import javax activation MimetypesFileTypeMap  public class MimeTest       public static void main String a              System out println new MimetypesFileTypeMap   getContentType             new File   path filename txt                This code produces the follow output  text plain

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I couldn t find anything to check for video mp4 MIME type so I made my own solution  I happened to observe that Wikipedia was wrong and that the 00 00 00 18 66 74 79 70 69 73 6F 6D file signature is not correct  the fourth byte  18  and all 70  excluded  after changes quite a lot amongst otherwise valid mp4 files  This code is essentially a copy paste of URLConnection guessContentTypeFromStream code but tailored to video mp4  BufferedInputStream bis   new BufferedInputStream new ByteArrayInputStream content    String mimeType   URLConnection guessContentTypeFromStream bis       Goes full barbaric and processes the bytes manually if  mimeType    null          These ints converted in hex ar         00 00 00 18 66 74 79 70 69 73 6F 6D        which are the file signature  magic bytes  for  mp4 files        from https   www wikiwand com en List of file signatures        just ctrl f  quot mp4 quot      int   mp4 sig    0  0  0  24  102  116  121  112        bis reset        bis mark 16       int   firstBytes   new int 8       for  int i   0  i  lt  8  i              firstBytes i    bis read                 This byte doesn t matter for the file signature and changes     mp4 sig 3    content 3        bis reset        if  Arrays equals firstBytes  mp4 sig            mimeType    quot video mp4 quot            Tested successfully against 10 different  mp4 files  EDIT  Here is a useful link  if it is still online  where you can find samples of many types  I don t own those videos  don t know who does either  but they re useful for testing the above code

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In Java 7 you can now just use Files probeContentType path

[java] Getting A File's Mime Type In Java

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