PST - Protocol Buffers String Templating

Abstract

PST allows to quickly generate Java Sourcecode from Protocol Buffer specifications by automating the process of boiler-plating, compilation and field definition via templates.

Building

Generally, PST is an integral part of the Apache Wave build process, and not called directly. If you want to build it, you can run

gradle build

but it'll usually will be built for your.

Standalone use

If you want to test PST directly, you'll need to build a standalone version with

gradle shadowJar

which allows you check out the example via

java -jar build/libs/wave-pst-0.1.jar -d example -f example/example.proto example/example.st

which will result in example/com/example/Person.java being created from the Protobuf definition of the Person schema in example/example.proto.

The boilerplate code will be coming from example/example.st, which references example/broto.st, providing the per-field code definitions.

Way of working

PST generates the corresponding java code using the following steps:

• protoc is called to create Java code from example/example.proto
• the resulting Example.java is compiled using javac
• each Message definition found in the Protocol Buffer file is matched against example/example.st
• the resulting Java code is passed through a styler to make it more human-readable

Use within Apache Wave

Apache Wave is using proto2 Protocol Buffers as documented in https://developers.google.com/protocol-buffers/docs/proto .. the task generateMessages in wave/build.gradle is responsible for combining String Templates as per http://www.stringtemplate.org/ to Java Classes.

A quick introduction to String Templates can be found under https://theantlrguy.atlassian.net/wiki/display/ST/Five+minute+Introduction