Serialization - Field Guide to Hadoop - page 41

Tutorial Links

Google provides excellent tutorials for a variety of languages in the official project docu-
mentation .

Example Code

Unlike Avro (described here ) , which supports runtime schema binding, protobuf must be in-
tegrated into your development and build process. You begin by defining a model in a .proto
file. For example:

message Review {
required string reviewer = 1;
required string movieTitle = 2;
required int32 rating = 3;

}

You then run a protobuf compiler for your specific development language (e.g., Java) to gen-
erate code based on your model definition.

The mechanism for working with the objects generated by the protobuf compiler changes
slightly from language to language. In Java, we use a builder to create a new, writeable ob-
ject:

Review . Builder reviewBuilder = Review . newBuilder ();
reviewBuilder . setReviewer ( "Kevin" );
reviewBuilder . setMovieTitle ( "Dune" );
reviewBuilder . setRating ( 10 );

Review review = reviewBuilder . build ();

This review object can then be written to any sort of output stream:

FileOutputStream output = new new FileOutputStream ( "review.dat" );

review . writeTo ( output );

Repopulating objects from previously serialized data is done in a similar fashion: