Convert InputStream to byte array in Java

Question

How do I read an entire InputStream into a byte array

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See the InputStream available   documentation      It is particularly important to realize that you must not use this   method to size a container and assume that you can read the entirety   of the stream without needing to resize the container  Such callers   should probably write everything they read to a ByteArrayOutputStream   and convert that to a byte array  Alternatively  if you re reading   from a file  File length returns the current length of the file    though assuming the file s length can t change may be incorrect    reading a file is inherently racy

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Here is an optimized version  that tries to avoid copying data bytes as much as possible   private static byte   loadStream  InputStream stream  throws IOException      int available   stream available       int expectedSize   available  gt  0   available   -1     return loadStream stream  expectedSize      private static byte   loadStream  InputStream stream  int expectedSize  throws IOException      int basicBufferSize   0x4000     int initialBufferSize    expectedSize  gt   0    expectedSize   basicBufferSize     byte   buf   new byte initialBufferSize      int pos   0     while  true          if  pos    buf length             int readAhead   -1           if  pos    expectedSize                readAhead   stream read             test whether EOF is at expectedSize             if  readAhead    -1                   return buf                                    int newBufferSize   Math max 2   buf length  basicBufferSize            buf   Arrays copyOf buf  newBufferSize            if  readAhead    -1                buf pos       byte readAhead                           int len   stream read buf  pos  buf length - pos         if  len  lt  0             return Arrays copyOf buf  pos                 pos    len

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public static byte   getBytesFromInputStream InputStream is  throws IOException       ByteArrayOutputStream os   new ByteArrayOutputStream         byte   buffer   new byte 0xFFFF       for  int len   is read buffer   len    -1  len   is read buffer              os write buffer  0  len             return os toByteArray

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Java 7 and later   import sun misc IOUtils      InputStream in        byte   buf   IOUtils readFully in  -1  false

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If you happen to use google guava  it ll be as simple as    byte   bytes   ByteStreams toByteArray inputStream

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You can try Cactoos   byte   array   new BytesOf stream  bytes

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I use this   public static byte   toByteArray InputStream is  throws IOException           ByteArrayOutputStream output   new ByteArrayOutputStream            try               byte   b   new byte 4096               int n   0              while   n   is read b      -1                    output write b  0  n                             return output toByteArray              finally               output close

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As always  also Spring framework  spring-core since 3 2 2  has something for you  StreamUtils copyToByteArray

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I know it s too late but here I think is cleaner solution that s more readable            method converts   link InputStream  Object into byte   array          param stream the   link InputStream  Object      return the byte   array representation of received   link InputStream  Object      throws IOException if an error occurs      public static byte   streamToByteArray InputStream stream  throws IOException        byte   buffer   new byte 1024       ByteArrayOutputStream os   new ByteArrayOutputStream         int line   0         read bytes from stream  and store them in buffer     while   line   stream read buffer      -1               Writes bytes from byte array  buffer  into output stream          os write buffer  0  line             stream close        os flush        os close        return os toByteArray

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You need to read each byte from your InputStream and write it to a ByteArrayOutputStream    You can then retrieve the underlying byte array by calling toByteArray     InputStream is       ByteArrayOutputStream buffer   new ByteArrayOutputStream     int nRead  byte   data   new byte 16384    while   nRead   is read data  0  data length      -1      buffer write data  0  nRead      return buffer toByteArray

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This is my copy-paste version    SuppressWarnings  empty-statement   public static byte   inputStreamToByte InputStream is  throws IOException       if  is    null            return null               Define a size if you have an idea of it      ByteArrayOutputStream r   new ByteArrayOutputStream 2048       byte   read   new byte 512      Your buffer size      for  int i  -1     i   is read read    r write read  0  i        is close        return r toByteArray

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Solution in Kotlin  will work in Java too  of course   which includes both cases of when you know the size or not       fun InputStream readBytesWithSize size  Long   ByteArray            return when               size  lt  0L - gt  this readBytes               size    0L - gt  ByteArray 0              size  gt  Int MAX VALUE - gt  null             else - gt                    val sizeInt   size toInt                   val result   ByteArray sizeInt                  readBytesIntoByteArray result  sizeInt                  result                                    fun InputStream readBytesIntoByteArray byteArray  ByteArray bytesToRead Int byteArray size            var offset   0         while  true                val read   this read byteArray  offset  bytesToRead - offset              if  read    -1                  break             offset    read             if  offset  gt   bytesToRead                  break                   If you know the size  it saves you on having double the memory used compared to the other solutions  in a brief moment  but still could be useful   That s because you have to read the entire stream to the end  and then convert it to a byte array  similar to ArrayList which you convert to just an array    So  if you are on Android  for example  and you got some Uri to handle  you can try to get the size using this       fun getStreamLengthFromUri context  Context  uri  Uri   Long           context contentResolver query uri  arrayOf MediaStore MediaColumns SIZE   null  null  null   use               if   it moveToNext                    return use             val fileSize   it getLong it getColumnIndex MediaStore MediaColumns SIZE               if  fileSize  gt  0                  return fileSize                     if you wish  you can also get the file-path from the uri here  and then try to get its size  using this  https   stackoverflow com a 61835665 878126         FileUtilEx getFilePathFromUri context  uri  false   use               val file   it file             val fileSize   file length               if  fileSize  gt  0                  return fileSize                   context contentResolver openInputStream uri   use   inputStream - gt              if  inputStream is FileInputStream                  return inputStream channel size               else                   var bytesCount   0L                 while  true                        val available   inputStream available                       if  available    0                          break                     val skip   inputStream skip available toLong                        if  skip  lt  0                          break                     bytesCount    skip                                   if  bytesCount  gt  0L                      return bytesCount                                 return -1L

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If you don t want to use the Apache commons-io library  this snippet is taken from the sun misc IOUtils class  It s nearly twice as fast as the common implementation using ByteBuffers   public static byte   readFully InputStream is  int length  boolean readAll          throws IOException       byte   output           if  length    -1  length   Integer MAX VALUE      int pos   0      while  pos  lt  length            int bytesToRead          if  pos  gt   output length       Only expand when there s no room             bytesToRead   Math min length - pos  output length   1024               if  output length  lt  pos   bytesToRead                    output   Arrays copyOf output  pos   bytesToRead                           else               bytesToRead   output length - pos                    int cc   is read output  pos  bytesToRead           if  cc  lt  0                if  readAll  amp  amp  length    Integer MAX VALUE                    throw new EOFException  Detect premature EOF                  else                   if  output length    pos                        output   Arrays copyOf output  pos                                     break                                  pos    cc            return output

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You re doing an extra copy if you use ByteArrayOutputStream  If you know the length of the stream before you start reading it  e g  the InputStream is actually a FileInputStream  and you can call file length   on the file  or the InputStream is a zipfile entry InputStream  and you can call zipEntry length     then it s far better to write directly into the byte   array -- it uses half the memory  and saves time      Read the file contents into a byte   array byte   buf   new byte inputStreamLength   int bytesRead   Math max 0  inputStream read buf        If needed  for safety  truncate the array if the file may somehow get    truncated during the read operation byte   contents   bytesRead    inputStreamLength   buf                     Arrays copyOf buf  bytesRead     N B  the last line above deals with files getting truncated while the stream is being read  if you need to handle that possibility  but if the file gets longer while the stream is being read  the contents in the byte   array will not be lengthened to include the new file content  the array will simply be truncated to the old length inputStreamLength

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We are seeing some delay for few AWS transaction  while converting S3 object to ByteArray   Note  S3 Object is PDF document  max size is 3 mb    We are using the option  1  org apache commons io IOUtils  to convert the S3 object to ByteArray  We have noticed S3 provide the inbuild IOUtils method to convert the S3 object to ByteArray  we are request you to confirm what is the best way to convert the S3 object to ByteArray to avoid the delay   Option  1   import org apache commons io IOUtils  is   s3object getObjectContent    content  IOUtils toByteArray is     Option  2   import com amazonaws util IOUtils  is   s3object getObjectContent    content  IOUtils toByteArray is     Also let me know if we have any other better way to convert the s3 object to bytearray

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You can use Apache Commons IO to handle this and similar tasks   The IOUtils type has a static method to read an InputStream and return a byte     InputStream is  byte   bytes   IOUtils toByteArray is     Internally this creates a ByteArrayOutputStream and copies the bytes to the output  then calls toByteArray    It handles large files by copying the bytes in blocks of 4KiB

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InputStream class InputStream   null  I am reading class from DB  class InputStream   rs getBinaryStream 1   Your Input stream could be from any source    int thisLine  ByteArrayOutputStream bos   new ByteArrayOutputStream    while   thisLine   class InputStream read       -1        bos write thisLine     bos flush    byte    yourBytes   bos toByteArray       Don t forget in the finally block to close ByteArrayOutputStream  amp  InputStream  In my case the IS is from resultset so just closing the rs will do it    if  bos    null       bos close

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Safe solution  with capability of close streams correctly    Java 9    final byte   bytes   try  inputStream         bytes   inputStream readAllBytes            Java 8   public static byte   readAllBytes InputStream inputStream  throws IOException        final int bufLen   4   0x400     4KB      byte   buf   new byte bufLen        int readLen       IOException exception   null        try            try  ByteArrayOutputStream outputStream   new ByteArrayOutputStream                   while   readLen   inputStream read buf  0  bufLen      -1                   outputStream write buf  0  readLen                 return outputStream toByteArray                      catch  IOException e             exception   e           throw e         finally            if  exception    null  inputStream close             else try                inputStream close               catch  IOException e                 exception addSuppressed e                             Kotlin  when Java 9  isn t accessible     Throws IOException  class   fun InputStream readAllBytes    ByteArray        val bufLen   4   0x400    4KB      val buf   ByteArray bufLen       var readLen  Int   0       ByteArrayOutputStream   use   o - gt           this use   i - gt               while  i read buf  0  bufLen  also   readLen   it      -1                   o write buf  0  readLen                       return o toByteArray              To avoid nested use see here      Scala  when Java 9  isn t accessible   By  Joan  Thx   def readAllBytes inputStream  InputStream   Array Byte      Stream continually inputStream read  takeWhile      -1  map   toByte  toArray

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The other case to get correct byte array via stream  after send request to server and waiting for the response                  Begin setup TCP connection to PC app            to open integrate connection between mobile app and pc app  or mobile app                      mSocket   new Socket IP  port             mSocket setSoTimeout 30000            DataOutputStream mDos   new DataOutputStream mSocket getOutputStream              String str    MobileRequest     params 0       lt EOF gt             mDos write str getBytes              try               Thread sleep 1000             catch  InterruptedException e                e printStackTrace                          Since data are accepted as byte  all of them will be collected in the         following byte array which initialised with accepted data length             DataInputStream mDis   new DataInputStream mSocket getInputStream             byte   data   new byte mDis available                 Collecting data into byte array         for  int i   0  i  lt  data length  i                data i    mDis readByte                Converting collected data in byte array into String          String RESPONSE   new String data

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This works for me   if inputStream    null                   ByteArrayOutputStream contentStream   readSourceContent inputStream                   String stringContent   contentStream toString                    byte   byteArr   encodeString stringContent                   readSourceContent    public static ByteArrayOutputStream readSourceContent InputStream inputStream  throws IOException           ByteArrayOutputStream outputStream   new ByteArrayOutputStream            int nextChar          try               while   nextChar   inputStream read       -1                    outputStream write nextChar                             outputStream flush              catch  IOException e                throw new IOException  Exception occurred while reading content   e                      return outputStream          encodeString    public static byte   encodeString String content  throws UnsupportedEncodingException           byte   bytes          try               bytes   content getBytes               catch  UnsupportedEncodingException e                String msg   ENCODING     is unsupported encoding type               log error msg e               throw new UnsupportedEncodingException msg  e                     return bytes

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Java 9 will give you finally a nice method   InputStream in        ByteArrayOutputStream bos   new ByteArrayOutputStream    in transferTo  bos    byte   bytes   bos toByteArray

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Do you really need the image as a byte    What exactly do you expect in the byte   - the complete content of an image file  encoded in whatever format the image file is in  or RGB pixel values   Other answers here show you how to read a file into a byte    Your byte   will contain the exact contents of the file  and you d need to decode that to do anything with the image data   Java s standard API for reading  and writing  images is the ImageIO API  which you can find in the package javax imageio  You can read in an image from a file with just a single line of code   BufferedImage image   ImageIO read new File  image jpg       This will give you a BufferedImage  not a byte    To get at the image data  you can call getRaster   on the BufferedImage  This will give you a Raster object  which has methods to access the pixel data  it has several getPixel     getPixels   methods    Lookup the API documentation for javax imageio ImageIO  java awt image BufferedImage  java awt image Raster etc   ImageIO supports a number of image formats by default  JPEG  PNG  BMP  WBMP and GIF  It s possible to add support for more formats  you d need a plug-in that implements the ImageIO service provider interface    See also the following tutorial  Working with Images

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Finally  after twenty years  there   s a simple solution without the need for a 3rd party library  thanks to Java  9   InputStream is      byte   array   is readAllBytes      Note also the convenience methods readNBytes byte   b  int off  int len  and transferTo OutputStream  addressing recurring needs

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Input Stream is     ByteArrayOutputStream bos   new ByteArrayOutputStream    int next   in read    while  next  gt  -1        bos write next       next   in read      bos flush    byte   result   bos toByteArray    bos close

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In new version  IOUtils readAllBytes inputStream

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I tried to edit  numan s answer with a fix for writing garbage data but edit was rejected  While this short piece of code is nothing brilliant I can t see any other better answer  Here s what makes most sense to me   ByteArrayOutputStream out   new ByteArrayOutputStream    byte   buffer   new byte 1024      you can configure the buffer size int length   while   length   in read buffer      -1  out write buffer  0  length     copy streams in close       call this in a finally block  byte   result   out toByteArray      btw ByteArrayOutputStream need not be closed  try finally constructs omitted for readability

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You can use cactoos library with provides reusable object-oriented Java components  OOP is emphasized by this library  so no static methods  NULLs  and so on  only real objects and their contracts  interfaces   A simple operation like reading InputStream  can be performed like that final InputStream input        final Bytes bytes   new BytesOf input   final byte   array   bytes asBytes    Assert assertArrayEquals      array      new byte   65  66  67      Having a dedicated type Bytes for working with data structure byte   enables us to use OOP tactics for solving tasks at hand  Something that a procedural  quot utility quot  method will forbid us to do  For example  you need to enconde bytes you ve read from this InputStream to Base64  In this case you will use Decorator pattern and wrap Bytes object within implementation for Base64  cactoos already provides such implementation  final Bytes encoded   new BytesBase64      new BytesOf          new InputStreamOf  quot XYZ quot            Assert assertEquals new TextOf encoded  asString     quot WFla quot     You can decode them in the same manner  by using Decorator pattern final Bytes decoded   new Base64Bytes      new BytesBase64          new BytesOf              new InputStreamOf  quot XYZ quot                      Assert assertEquals new TextOf decoded  asString     quot XYZ quot     Whatever your task is you will be able to create own implementation of Bytes to solve it

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Use vanilla Java s DataInputStream and its readFully Method  exists since at least Java 1 4        byte   bytes   new byte  int  file length     DataInputStream dis   new DataInputStream new FileInputStream file    dis readFully bytes         There are some other flavors of this method  but I use this all the time for this use case

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Wrap it in a DataInputStream if that is off the table for some reason  just use read to hammer on it until it gives you a -1 or the entire block you asked for   public int readFully InputStream in  byte   data  throws IOException       int offset   0      int bytesRead      boolean read   false      while   bytesRead   in read data  offset  data length - offset      -1            read   true          offset    bytesRead          if  offset  gt   data length                break                      return  read    offset   -1

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Below Codes  public static byte   serializeObj Object obj  throws IOException     ByteArrayOutputStream baOStream   new ByteArrayOutputStream      ObjectOutputStream objOStream   new ObjectOutputStream baOStream      objOStream writeObject obj      objOStream flush      objOStream close      return baOStream toByteArray          OR  BufferedImage img       ByteArrayOutputStream baos   new ByteArrayOutputStream 1000   ImageIO write img   jpeg   baos   baos flush    byte   result   baos toByteArray    baos close

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ByteArrayOutputStream out   new ByteArrayOutputStream    byte   buffer   new byte 1024   while  true        int r   in read buffer       if  r    -1  break      out write buffer  0  r      byte   ret   out toByteArray

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Adamski  You can avoid buffer entirely   Code copied from http   www exampledepot com egs java io File2ByteArray html  Yes  it is very verbose  but needs half the size of memory as the other solution       Returns the contents of the file in a byte array  public static byte   getBytesFromFile File file  throws IOException       InputStream is   new FileInputStream file           Get the size of the file     long length   file length            You cannot create an array using a long type         It needs to be an int type         Before converting to an int type  check        to ensure that file is not larger than Integer MAX VALUE      if  length  gt  Integer MAX VALUE               File is too large               Create the byte array to hold the data     byte   bytes   new byte  int length           Read in the bytes     int offset   0      int numRead   0      while  offset  lt  bytes length             amp  amp   numRead is read bytes  offset  bytes length-offset    gt   0            offset    numRead                Ensure all the bytes have been read in     if  offset  lt  bytes length            throw new IOException  Could not completely read file   file getName                   Close the input stream and return bytes     is close        return bytes

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In-case someone is still looking for a solution without dependency and If you have a file   DataInputStream   byte   data   new byte  int  file length      DataInputStream dis   new DataInputStream new FileInputStream file     dis readFully data    dis close      ByteArrayOutputStream   InputStream is   new FileInputStream file    ByteArrayOutputStream buffer   new ByteArrayOutputStream     int nRead   byte   data   new byte  int  file length      while   nRead   is read data  0  data length      -1         buffer write data  0  nRead        RandomAccessFile   RandomAccessFile raf   new RandomAccessFile file   quot r quot     byte   data   new byte  int  raf length      raf readFully data

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Java 8 way  thanks to BufferedReader and Adam Bien   private static byte   readFully InputStream input  throws IOException       try  BufferedReader buffer   new BufferedReader new InputStreamReader input              return buffer lines   collect Collectors joining   n    getBytes  lt charset can be specified gt              Note that this solution wipes carriage return    r   and can be inappropriate

[java] Convert InputStream to byte array in Java

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