Month: August 2016

Dynamically Instantiating Classes in Python

Posted on by rchapin

A common design pattern is to define a class or list of classeses in configuration such that at runtime the classes can be dynamically instantiated.

I’ve done this before in many other languages and had need to do so today in Python (2.7.11)

It seems as though the clean way to do so is by using the Pyton importlib module.  By using it, it enables you to cleanly dynamically import sub modules

Following is an example:

import importlib

klass_1_module =
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Java PowerMock Could not reconfigure JMX java.lang.LinkageError Solution

Posted on by rchapin

If you are using Mockito and PowerMock to build mocks for your Java tests and you run into the following error:

2016-05-05 17:31:20,204 main ERROR Could not reconfigure JMX java.lang.LinkageError: loader constraint violation: loader (instance of org/powermock/core/classloader/MockClassLoader) previously initiated loading for a different type with name "javax/management/MBeanServer"
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
        at org.powermock.core.classloader.MockClassLoader.loadUnmockedClass(MockClassLoader.java:238)
        at org.powermock.core.classloader.MockClassLoader.loadModifiedClass(MockClassLoader.java:182)
        at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass(DeferSupportingClassLoader.java:70)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

Simply add the following as a class level annotation:

@PowerMockIgnore( {"javax.management.*"} )

→ Continue reading “Java PowerMock Could not reconfigure JMX java.lang.LinkageError Solution”

© 2005 Ryan Chapin