How do you embed binary data in XML?

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I have two applications written in Java that communicate with each other using XML messages over the network. I'm using a SAX parser at the receiving end to get the data back out of the messages. One of the requirements is to embed binary data in an XML message, but SAX doesn't like this. Does anyone know how to do this?

UPDATE: I got this working with the Base64 class from the apache commons codec library, in case anyone else is trying something similar.

12 Answers

XML is so versatile...

<DATA>
  <BINARY>
    <BIT index="0">0</BIT>
    <BIT index="1">0</BIT>
    <BIT index="2">1</BIT>
    ...
    <BIT index="n">1</BIT>
  </BINARY>
</DATA>

XML is like violence - If it doesn't solve your problem, you're not using enough of it.

EDIT:

BTW: Base64 + CDATA is probably the best solution

(EDIT2:
Whoever upmods me, please also upmod the real answer. We don't want any poor soul to come here and actually implement my method because it was the highest ranked on SO, right?)

Base64 is indeed the right answer but CDATA is not, that's basically saying: "this could be anything", however it must not be just anything, it has to be Base64 encoded binary data. XML Schema defines Base 64 binary as a primitive datatype which you can use in your xsd.

Try Base64 encoding/decoding your binary data. Also look into CDATA sections

Maybe encode them into a known set - something like base 64 is a popular choice.

You can also Uuencode you original binary data. This format is a bit older but it does the same thing as base63 encoding.

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