<< Back to previous view

[CLJ-978] bean unable to handle non-public classes Created: 30/Apr/12  Updated: 05/Feb/14

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: Release 1.4
Fix Version/s: None

Type: Enhancement Priority: Major
Reporter: Charles Duffy Assignee: Unassigned
Resolution: Unresolved Votes: 2
Labels: None

Attachments: File clojure--bean-support-for-private-implementation-classes-v3.diff    
Patch: Code and Test

 Description   

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$bean$fn__1827$fn__1828 can not access a member of class FooImpl with modifiers "public"
 at sun.reflect.Reflection.ensureMemberAccess (Reflection.java:65)
    java.lang.reflect.Method.invoke (Method.java:588)
    clojure.core$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>.



 Comments   
Comment by Charles Duffy [ 30/Apr/12 10:40 PM ]

Fix inaccurate documentation string

Comment by Charles Duffy [ 01/May/12 9:41 AM ]

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.

Comment by Charles Duffy [ 01/May/12 10:11 AM ]

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

Comment by Andy Fingerhut [ 04/May/12 2:48 AM ]

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.

Comment by Charles Duffy [ 06/May/12 2:59 PM ]

Added a patch created per documented process.

Comment by Gary Trakhman [ 04/Oct/12 6:44 PM ]

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)))

Comment by Rich Hickey [ 29/Nov/12 10:01 AM ]

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.

Generated at Wed Apr 23 17:34:24 CDT 2014 using JIRA 4.4#649-r158309.