Accessing private methods and fields of a Java class

//This class uses reflection to enable you to invoke private methods on a class, or access its private fields. This can be useful for unit testing.
import java.lang.reflect.Field;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;
import junit.framework.Assert;
/** * Provides access to private members in classes. */public class PrivateAccessor {
public static Object getPrivateField (Object o, String fieldName) { // Check we have valid arguments... Assert.assertNotNull(o); Assert.assertNotNull(fieldName);
// Go and find the private field... final Field fields[] = o.getClass().getDeclaredFields(); for (int i = 0; i < fields.length; ++i) { if (fieldName.equals(fields[i].getName())) { try { fields[i].setAccessible(true); return fields[i].get(o); } catch (IllegalAccessException ex) { Assert.fail ("IllegalAccessException accessing " + fieldName); } } } Assert.fail ("Field '" + fieldName +"' not found"); return null; }
public static Object invokePrivateMethod (Object o, String methodName, Object[] params) { // Check we have valid arguments... Assert.assertNotNull(o); Assert.assertNotNull(methodName); Assert.assertNotNull(params);
// Go and find the private method... final Method methods[] = o.getClass().getDeclaredMethods(); for (int i = 0; i < methods.length; ++i) { if (methodName.equals(methods[i].getName())) { try { methods[i].setAccessible(true); return methods[i].invoke(o, params); } catch (IllegalAccessException ex) { Assert.fail ("IllegalAccessException accessing " + methodName); } catch (InvocationTargetException ite) { Assert.fail ("InvocationTargetException accessing " + methodName); } } } Assert.fail ("Method '" + methodName +"' not found"); return null; }}