How to (base64) encode a protobuf as a String

Question

I have a protobuf and want to encode its binary representation in base64 (or another textual encoding) for transmission over a text protocol. What's the cleanest way to do that?

Answer 1

The easiest option is to convert your proto to a byte[] and then use Guava's BaseEncoding class to encode those bytes as a base64 string:

String asBase64 = BaseEncoding.base64().encode(proto.toByteArray());

This is the most straightforward, but there are a number of other roughly equivalent mechanisms. For example if you want to write the encoded data to a file or other writable resource, you could write it to an OutputStream returned by BaseEncoding.encodingStream():

proto.writeTo(BaseEncoding.base64().encodingStream(fileWriter));

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As of Java 8 there's also java.util.Base64, if you're not using Guava. See encode(byte[]) and wrap(OutputStream).

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As Jon Skeet mentioned, proto3 can map to and from JSON if you don't explicitly need to transmit the data in binary format (and you're using proto3, of course).