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up vote 1 down vote favorite

On my java server I get from an iOS client an InputStream, which looks like this:

--0xKhTmLbOuNdArY
Content-Disposition: form-data; filename="Image001"
Content-Type: image/png

âPNG
IHDR���@���@���™iqfi���gAMA��Ø»7äÈ���tEXtSoftware�Adobe ImageReadyq…e<��IDATx⁄‰;iê]Uôflπ˜Ω◊Ø;ΩB::õY
ê6LÄ“Õ¿
... etc. ...
≠Yy<‘_˜øüYmc˚æØ…ægflóÏK$å±çe0ˆΩleIë¢êH¢Tñê–Üd
≠≤§àä6D¸>˙÷˜˚<øÁ˘˝˜˚º^sÁ=Áû{ÓπÁ‹œπ˜úÄÎ:!44¡@
--0xKhTmLbOuNdArY--

The first and last line are my HTTP Boundary. In line 2 and 3 are Information about the image file. And from line 5 until the penultimate line there is the image file which I need as a byte array.

So how do I get the image information as a String and the image file as a byte array from the InputStream? The solution should be fast and efficient (The file size can be several megabytes / < 10 MB ).

My approach:

I convert the InputStream to a String, then split it and convert the second String to byte array...

String str = org.apache.commons.io.IOUtils.toString( inputStream );
String[] strArray1 = str.split( "\r\n\r\n", 2 );
byte[] bytes = strArray1[1].getBytes();

That way is very fast, but the byte array seems to be damaged. I can not create an image file from that byte array... Some characters are incorrectly converted.

Perhaps someone can help?

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2 Answers

up vote 1 down vote

The reason why your code breaks is the first line:

String str = org.apache.commons.io.IOUtils.toString( inputStream );

Trying to convert random bytes into Unicode characters, and then back to the same random bytes, isn't going to work.

The only way you can make this work is by reading the input in stages, rather than reading it all into a String.

  1. Read from the InputStream until you're convinced you're past the HTTP boundary line.
  2. Read the rest of the stream into a byte array (you can use IOUtils for that, too).
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up vote 1 down vote

You probably don't want to convert your bytes to char and back, that would destroy your bytes as the byte stream doesn't correspond to any encoding.

I would read the whole thing in as a byte[] using IOUtils.toByteArray, then look for the byte sequence "\r\n\r\n".getBytes() in that array.

Note that IOUtils.toByteArray doesn't stop until end-of-stream. This should be fine for HTTP 1.0, but will break for HTTP 1.1 which can send multiple requests on the same stream. In that case, you'll have to read incrementally to find the Content-Length field so you know how much of the InputStream to read.

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