Determine the size of an InputStream

Question

My current situation is  I have to read a file and put the contents into InputStream  Afterwards I need to place the contents of the InputStream into a byte array which requires  as far as I know  the size of the InputStream  Any ideas   As requested  I will show the input stream that I am creating from an uploaded file  InputStream uploadedStream   null  FileItemFactory factory   new DiskFileItemFactory    ServletFileUpload upload   new ServletFileUpload factory   java util List items   upload parseRequest request         java util Iterator iter   items iterator     while  iter hasNext          FileItem item    FileItem  iter next        if   item isFormField              uploadedStream   item getInputStream              CHANGE uploadedStreambyte   item get             The request is a HttpServletRequest object  which is like the FileItemFactory and ServletFileUpload is from the Apache Commons FileUpload package

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When explicitly dealing with a ByteArrayInputStream then contrary to some of the comments on this page you can use the  available   function to get the size  Just have to do it before you start reading from it   From the JavaDocs      Returns the number of remaining bytes that can be read  or skipped   over  from this input stream  The value returned is count - pos  which   is the number of bytes remaining to be read from the input buffer    https   docs oracle com javase 7 docs api java io ByteArrayInputStream html available

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try           InputStream connInputStream   connection getInputStream          catch  IOException e            e printStackTrace               int size   connInputStream available      int available    Returns an estimate of the number of bytes that can be read  or skipped over  from this input stream without blocking by the next invocation of a method for this input stream  The next invocation might be the same thread or another thread  A single read or skip of this many bytes will not block  but may read or skip fewer bytes   InputStream - Android SDK   Android Developers

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For InputStream org apache commons io IoUtils toByteArray inputStream  length    For Optional  lt  MultipartFile  gt  Stream of multipartFile get    mapToLong file- gt file getSize    findFirst   getAsLong

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You can t determine the amount of data in a stream without reading it  you can  however  ask for the size of a file   http   java sun com javase 6 docs api java io File html length    If that isn t possible  you can write the bytes you read from the input stream to a ByteArrayOutputStream which will grow as required

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I would read into a ByteArrayOutputStream and then call toByteArray   to get the resultant byte array  You don t need to define the size in advance  although it s possibly an optimisation if you know it  In many cases you won t

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If you know that your InputStream is a FileInputStream or a ByteArrayInputStream  you can use a little reflection to get at the stream size without reading the entire contents  Here s an example method   static long getInputLength InputStream inputStream        try           if  inputStream instanceof FilterInputStream                FilterInputStream filtered    FilterInputStream inputStream              Field field   FilterInputStream class getDeclaredField  in                field setAccessible true               InputStream internal    InputStream  field get filtered               return getInputLength internal             else if  inputStream instanceof ByteArrayInputStream                ByteArrayInputStream wrapper    ByteArrayInputStream inputStream              Field field   ByteArrayInputStream class getDeclaredField  buf                field setAccessible true               byte   buffer    byte   field get wrapper               return buffer length            else if  inputStream instanceof FileInputStream                FileInputStream fileStream    FileInputStream inputStream              return fileStream getChannel   size                    catch  NoSuchFieldException   IllegalAccessException   IOException exception               Ignore all errors and just return -1            return -1      This could be extended to support additional input streams  I am sure

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I just wanted to add  Apache Commons IO has stream support utilities to perform the copy   Btw  what do you mean by placing the file into an inputstream  Can you show us your code    Edit   Okay  what do you want to do with the contents of the item  There is an item get   which returns the entire thing in a byte array   Edit2  item getSize   will return the uploaded file size

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This is a REALLY old thread  but it was still the first thing to pop up when I googled the issue   So I just wanted to add this   InputStream inputStream   conn getInputStream    int length   inputStream available      Worked for me   And MUCH simpler than the other answers here     Warning This solution does not provide reliable results regarding the total size of a stream  Except from the JavaDoc      Note that while some implementations of   code InputStream  will return          the total number of bytes in the stream  many will not

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Use this method  you just have to pass the InputStream  public String readIt InputStream is        if  is    null            BufferedReader reader   new BufferedReader new InputStreamReader is   utf-8    8            StringBuilder sb   new StringBuilder            String line          while   line   reader readLine       null                sb append line  append   n                      is close            return sb toString              return  error

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you can get the size of InputStream using getBytes inputStream  of Utils java check this following link  Get Bytes from Inputstream

[java] Determine the size of an InputStream

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