Interesting Java integration phenomenon

Ruby JRuby
1

While I was constructing a test case to try and reproduce another
problem (which turned out to be fixed) I encountered something rather
interesting.

shard:jruby trejkaz$ cat A.java
public class A {
    public String getPublic() {
        return "public";
    }
    public String getPublic1() {
        return "public";
    }
}
shard:jruby trejkaz$ javac A.java
shard:jruby trejkaz$ jar cf a.jar A.class
shard:jruby trejkaz$ java -jar jruby-complete-1.4.0RC3.jar -S irb
irb(main):001:0> require 'a.jar'
=> true
irb(main):002:0> include_class 'A'
=> ["A"]
irb(main):003:0> a = A.new
=> #<Java::Default::A:0x39060b>
irb(main):004:0> a.public
NoMethodError: undefined method `public' for

#Java::Default::A:0x39060b
from (irb):5
irb(main):005:0> a.public1
=> “public”
irb(main):006:0>

From the outside it’s not obvious why ‘public’ would be special like
this, it just happened to be the first name I choose for the method I
was testing at the time. Ruby objects don’t have anything special
called ‘public’ and neither do Java objects, which is why this seemed
interesting to me.

TX

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2

Well had it been a static method I think the answer would have been
that ‘public’ is a method on Module. Since this is calling on an
instance method, I am guessing maybe ‘public’ is in RESERVED_NAMES
when it should be in STATIC_RESERVED_WORDS. Can you file a bug on
this?

The background is that for a small set of important Ruby methods we
will not override their definition in case of conflict. ‘public’ is
in this list.

As a workaround you can use ‘java_send’ to still call the method…

-Tom

On Sat, Oct 31, 2009 at 10:41 PM, Trejkaz [email protected] wrote:

       return "public";

=> #Java::Default::A:0x39060b
called ‘public’ and neither do Java objects, which is why this seemed

–
blog: http://blog.enebo.com twitter: tom_enebo
mail: [email protected]

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3

On Mon, Nov 2, 2009 at 2:52 AM, Thomas E Enebo [email protected]
wrote:

Well had it been a static method I think the answer would have been
that ‘public’ is a method on Module. Â Since this is calling on an
instance method, I am guessing maybe ‘public’ is in RESERVED_NAMES
when it should be in STATIC_RESERVED_WORDS. Â Can you file a bug on
this?

Filed: http://jira.codehaus.org/browse/JRUBY-4198

The background is that for a small set of important Ruby methods we
will not override their definition in case of conflict. Â ‘public’ is
in this list.

As a workaround you can use ‘java_send’ to still call the method…

For our real system, we are deliberately trying to avoid using names
which are generic enough to cause conflicts (both in JRuby and –
hopefully – in whatever other scripting languages users might use.)
I found this purely by chance and thought it was interesting.

TX

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