Use a template library for the SpecificCompiler
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Key: AVRO-648
URL: https://issues.apache.org/jira/browse/AVRO-648
Project: Avro
Issue Type: Improvement
Components: java
Reporter: Philip Zeyliger
Assignee: Philip Zeyliger
This JIRA proposes uses a templating library instead of string concatenation
for the SpecificCompiler.
We've had conversations on the list about customizing the generated code (by
adding getters and setters, adding utility classes for the arrays, adding
String-friendly (as opposed to Utf8) accessors, etc.), but we've been stymied
by the fact that the specific compiler is hard-coded to use one template, and
it's hard to experiment with. Sam Pullara (at
http://github.com/spullara/avrocompiler) has done pretty much this: he
forked/subclassed a copy of SpecificCompiler that uses the Mustache language to
generate code. He's also gone ahead and done some of the customizations.
In the patch I'm about to post, I've replicated the existing code generation
using Velocity. We already build Velocity for some of the IPC plugins, and
it's an Apache project. The existing tests pass, plus I've added tests that
check that the generated code is character-for-character the same, in a handful
of cases. This was actually quite painful, since I had to reproduce some
questionable indentation and trailing whitespace :). That said, I'm pleased
with how easy it was to incorporate the templates.
Eventually, I hope we support getters and setters, or perhaps support multiple
versions of templates. (If someone wants to generate, say, C++ code, the path
is now a lot easier for that, as well.)
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