Field annotations #624

merged 4 commits into from May 21, 2013


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4 participants

daicoden commented Apr 2, 2013

Let me know what you think of adding this functionality and if you have any better ideas for generate_java_fields.

This allows you to define an object in ruby and add field annotations. A use case is to create an object in ruby and pass it to a transformation library which uses fields and annotations for seralization.

@headius headius was assigned Apr 2, 2013

Here is some documentation of java_field for the wiki (enclosed as a diff, as I couldn't find a better way to supply wiki changes as part of a pull request). I did not succeed in writing, and testing, a similar one for add_field_annotation. I don't know why my attempts failed, but I do have one question: what should add_field_annotation do if passed a name which does not exist? It seems to silently fail now.

diff --git a/ b/
index 7c0d088..0921838 100644
--- a/
+++ b/
@@ -39,6 +39,25 @@ end

 The resulting Java class has an instance method named ```some_method``` and a static method named ```class_method```.

+Similarly, you can add java fields:
+class Bar
+  java_field "java.lang.String name"
+  become_java!
+b = = "chin-up"
+# =>
+# "chin-up" = 234
+# raises IllegalArgumentException
+The type of a Java field currently must be a non-primitive type (for example, java.lang.Object not int).
 Generating Java Classes Ahead-of-time


This continue null check should be moved above fieldVisitor since we won't use it if we continue.


Quick clarifying question, I'm not 100% sure how ASM works. Don't we need to visit the field here even if there are no annotations so we at least create a public field of that name on the reified class? Or does line 1357 fail to accomplish this?

gah. You are right. I conflated anno processing here with field creation. Ignore my comment (and Charles already merged this)

enebo commented May 20, 2013

[Note: I made comment on 48938ee which would be nice to be addressed]

I find this a reasonable starting point and I think we can merge this as-is, but I feel this is an incomplete feature as it would be nice if we could use the equivalent of java_signature() instead of the more procedural mechanism we have in place. It would see a day where we can have:

java_field '@Persistent @Synchronized Integer baz'

I suspect JavaSignatureParser needs some work to process field signatures but it is my hope eventually the above signature is the only way we add stuff. I mostly mention this is anyone wants to look into JavaSignatureParser and allow a more cut-and-paste signature format.

headius commented May 21, 2013

I'm going to go ahead and merge this, since it seems like a good start. I agree with @enebo that we should (with your help) continue to build out this functionality and also try to expand tests to more complex cases.

@headius headius merged commit e33a5b6 into jruby:master May 21, 2013

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