java net URL read stream to byte

Question

I m trying to read an image from an URL  with the java package  java net URL  to a byte     Everything  works fine  except that the content isnt being enterely read from the stream  the image is corrupt  it doesnt contain all the image data     The byte array is being persisted in a database  BLOB   I really dont know what the correct approach is  maybe you can give me a tip     This is my first approach  code formatted  removed unnecessary informations       URL u   new URL  http   localhost 8080 images anImage jpg    int contentLength   u openConnection   getContentLength    Inputstream openStream   u openStream    byte   binaryData   new byte contentLength   openStream read binaryData   openStream close      My second approach was this one  as you ll see the contentlength is being fetched another way    URL u   new URL content   openStream   u openStream    int contentLength   openStream available    byte   binaryData   new byte contentLength   openStream read binaryData   openStream close      Both of the code result in a corrupted image    I already read this post from stackoverflow

User · Answer

It s important to specify timeouts  especially when the server takes to respond  With pure Java  without using any dependency   public static byte   copyURLToByteArray final String urlStr          final int connectionTimeout  final int readTimeout                   throws IOException       final URL url   new URL urlStr       final URLConnection connection   url openConnection        connection setConnectTimeout connectionTimeout       connection setReadTimeout readTimeout       try  InputStream input   connection getInputStream                ByteArrayOutputStream output   new ByteArrayOutputStream              final byte   buffer   new byte 8192           for  int count   count   input read buffer    gt  0                 output write buffer  0  count                     return output toByteArray              Using dependencies  e g   HC Fluent   public byte   copyURLToByteArray final String urlStr          final int connectionTimeout  final int readTimeout                  throws IOException       return Request Get urlStr               connectTimeout connectionTimeout               socketTimeout readTimeout               execute                returnContent                asBytes

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I am very surprised that nobody here has mentioned the problem of connection and read timeout  It could happen  especially on Android and or with some crappy network connectivity  that the request will hang and wait forever   The following code  which also uses Apache IO Commons  takes this into account  and waits max  5 seconds until it fails   public static byte   downloadFile URL url        try           URLConnection conn   url openConnection            conn setConnectTimeout 5000           conn setReadTimeout 5000           conn connect              ByteArrayOutputStream baos   new ByteArrayOutputStream            IOUtils copy conn getInputStream    baos            return baos toByteArray              catch  IOException e                   Log error and return null  some default or throw a runtime exception

User · Answer

The content length is just a HTTP header  You cannot trust it  Just read everything you can from the stream    Available is definitely wrong  It s just the number of bytes that can be read without blocking   Another issue is your resource handling  Closing the stream has to happen in any case  try catch finally will do that

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Here s a clean solution   private byte   downloadUrl URL toDownload        ByteArrayOutputStream outputStream   new ByteArrayOutputStream         try           byte   chunk   new byte 4096           int bytesRead          InputStream stream   toDownload openStream             while   bytesRead   stream read chunk    gt  0                outputStream write chunk  0  bytesRead                    catch  IOException e            e printStackTrace            return null             return outputStream toByteArray

User · Answer

Use commons-io IOUtils toByteArray URL    String url    http   localhost 8080 images anImage jpg   byte   fileContent   IOUtils toByteArray new URL url      Maven dependency    lt dependency gt       lt groupId gt commons-io lt  groupId gt       lt artifactId gt commons-io lt  artifactId gt       lt version gt 2 6 lt  version gt   lt  dependency gt

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byte   b   IOUtils toByteArray  new URL     openStream       idiom   Note however  that stream is not closed in the above example   if you want a  76-character  chunk  using commons codec      byte   b   Base64 encodeBase64 IOUtils toByteArray  new URL     openStream     true

User · Answer

There s no guarantee that the content length you re provided is actually correct   Try something akin to the following   ByteArrayOutputStream baos   new ByteArrayOutputStream    InputStream is   null  try     is   url openStream       byte   byteChunk   new byte 4096      Or whatever size you want to read in at a time    int n     while    n   is read byteChunk    gt  0         baos write byteChunk  0  n         catch  IOException e      System err printf   Failed while reading bytes from  s   s   url toExternalForm    e getMessage       e printStackTrace          Perform any other exception handling that s appropriate    finally     if  is    null    is close          You ll then have the image data in baos  from which you can get a byte array by calling baos toByteArray     This code is untested  I just wrote it in the answer box   but it s a reasonably close approximation to what I think you re after

User · Answer

Just extending Barnards s answer with commons-io  Separate answer because I can not format code in comments    InputStream is   null  try     is   url openStream       byte   imageBytes   IOUtils toByteArray is     catch  IOException e      System err printf   Failed while reading bytes from  s   s   url toExternalForm    e getMessage       e printStackTrace          Perform any other exception handling that s appropriate    finally     if  is    null    is close          http   commons apache org io api-1 4 org apache commons io IOUtils html toByteArray java io InputStream

[java] java.net.URL read stream to byte[]

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