bean unable to handle non-public classes

Question

Take the following Java as an example:

`
public interface IFoo {
String getBar();
}

class FooImpl {
String getBar() { return "bar"; }
}
`

As presently implemented, {{(bean my-foo)}} tries to invoke the following:

(. #<Method public java.lang.String FooImpl.getBar> (invoke my-foo nil))

However, as {{FooImpl}} is not public, this fails:

`
java.lang.IllegalAccessException: Class clojure.core$bean$fn1827$fn1828 can not access a member of class FooImpl with modifiers "public"
at sun.reflect.Reflection.ensureMemberAccess (Reflection.java:65)

java.lang.reflect.Method.invoke (Method.java:588)
clojure.core$bean$fn__1827$fn__1828.invoke (core_proxy.clj:382)
clojure.core$bean$v__1832.invoke (core_proxy.clj:388)
clojure.core$bean$fn__1838$thisfn__1839$fn__1840.invoke (core_proxy.clj:406)
clojure.lang.LazySeq.sval (LazySeq.java:42)
clojure.lang.LazySeq.seq (LazySeq.java:60)
clojure.lang.RT.seq (RT.java:473)

`

However, the same thing succeeds if we call #<Method public java.lang.String Foo.getBar> rather than #<Method public java.lang.String FooImpl.getBar>.

Answer 1

Comment made by: charles-dyfis-net

Fix inaccurate documentation string

Answer 2

Comment made by: charles-dyfis-net

Apache Commons Beanutils has their own implementation of this, at http://www.docjar.com/html/api/org/apache/commons/beanutils/MethodUtils.java.html#771 -- notably, it tries to reflect a method with the given signature and catches the exception on failure, rather than iterating through the whole list. This may be a better approach -- I'm unfamiliar with how the cost of exception handling compares with that of reflecting on the full method list of a class.

Answer 3

Comment made by: charles-dyfis-net

Prior version of patch were missing new test suite files. Corrected.

Answer 4

Comment made by: jafingerhut

Thanks for the patches, Charles. Could you please create a patch in the desired format and attach that, and then remove the obsolete patches? Instructions for creating a patch are under the heading "Development" at this page: http://dev.clojure.org/display/design/JIRA workflow

Instructions for removing patches are under the heading "Removing patches" on that same page.

Answer 5

Comment made by: charles-dyfis-net

Added a patch created per documented process.

Answer 6

Comment made by: gtrak

I found in my code that it's possible to get a NPE if there is no read-method, for instance on the http://docs.cascading.org/cascading/2.0/javadoc/cascading/flow/hadoop/HadoopFlow.html object which has a setCascade method but no getter. I fixed this in our code by inlining the is-zero-args check into the public-method definition and and-ing the whole thing with 'method' like the original 'bean' code, like so:

public-method (and method (zero? (alength (. method (getParameterTypes))))

              (or (and (java.lang.reflect.Modifier/isPublic (. c (getModifiers)))
                                                       method)
                                                  (public-version-of-method method)))

Answer 7

Comment made by: richhickey

Charles, I think we should follow Apache BeanUtils on this. Exceptions not thrown are cheap. Ordinarily, exception for control flow are bad, but this is forced by bad design of reflection API.

Answer 8

Reference: https://clojure.atlassian.net/browse/CLJ-978 (reported by charles-dyfis-net)