Update:
Some 10 years later perhaps the best way to test a private method, or any inaccessible member, is via @Jailbreak
from the Manifold framework.
@Jailbreak Foo foo = new Foo();
// Direct, *type-safe* access to *all* foo's members
foo.privateMethod(x, y, z);
foo.privateField = value;
This way your code remains type-safe and readable. No design compromises, no overexposing methods and fields for the sake of tests.
If you have somewhat of a legacy Java application, and you're not allowed to change the visibility of your methods, the best way to test private methods is to use reflection.
Internally we're using helpers to get/set private
and private static
variables as well as invoke private
and private static
methods. The following patterns will let you do pretty much anything related to the private methods and fields. Of course, you can't change private static final
variables through reflection.
Method method = TargetClass.getDeclaredMethod(methodName, argClasses);
method.setAccessible(true);
return method.invoke(targetObject, argObjects);
And for fields:
Field field = TargetClass.getDeclaredField(fieldName);
field.setAccessible(true);
field.set(object, value);
Notes:
1. TargetClass.getDeclaredMethod(methodName, argClasses)
lets you look into private
methods. The same thing applies for
getDeclaredField
.
2. The setAccessible(true)
is required to play around with privates.
Best Answer
The relevant documentation can be found here:
http://java.sun.com/javase/6/docs/technotes/guides/management/agent.html
Start your program with following parameters:
For instance like this:
-Dcom.sun.management.jmxremote.local.only=false
is not necessarily required but without it, it doesn't work on Ubuntu. The error would be something like this:see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6754672
Also be careful with
-Dcom.sun.management.jmxremote.authenticate=false
which makes access available for anyone, but if you only use it to track the JVM on your local machine it doesn't matter.Update:
In some cases I was not able to reach the server. This was then fixed if I set this parameter as well:
-Djava.rmi.server.hostname=127.0.0.1