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JMockit is a Java toolkit for automated developer testing. It contains mocking/faking APIs and a code coverage tool, supporting both JUnit and TestNG. The mocking APIs allow all kinds of Java code, without testability restrictions, to be tested in isolation from selected dependencies.
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/*
 * Copyright (c) 2006 JMockit developers
 * This file is subject to the terms of the MIT license (see LICENSE.txt).
 */
package mockit;

import static java.lang.reflect.Modifier.*;

import mockit.internal.classGeneration.*;
import mockit.internal.reflection.*;
import mockit.internal.reflection.EmptyProxy.*;

/**
 * Provides utility methods that enable access to ("de-encapsulate") otherwise non-accessible fields.
 *
 * @see #getField(Object, String)
 * @see #setField(Object, String, Object)
 */
public final class Deencapsulation
{
   private Deencapsulation() {}

   /**
    * Gets the value of a non-accessible (eg private) field from a given object.
    *
    * @param objectWithField the instance from which to get the field value
    * @param fieldName the name of the field to get
    * @param  interface or class type to which the returned value should be assignable
    *
    * @throws IllegalArgumentException if the desired field is not found
    *
    * @see #getField(Object, Class)
    * @see #getField(Class, String)
    * @see #setField(Object, String, Object)
    */
   public static  T getField(Object objectWithField, String fieldName) {
      return FieldReflection.getField(objectWithField.getClass(), fieldName, objectWithField);
   }

   /**
    * Gets the value of a non-accessible (eg private) field from a given object, assuming there is
    * only one field declared in the class of the given object whose type can receive values of the specified field
    * type.
    *
    * @param objectWithField the instance from which to get the field value
    * @param fieldType the declared type of the field, or a sub-type of the declared field type
    *
    * @throws IllegalArgumentException if either the desired field is not found, or more than one is
    *
    * @see #getField(Object, String)
    * @see #getField(Class, String)
    * @see #setField(Object, Object)
    */
   public static  T getField(Object objectWithField, Class fieldType) {
      return FieldReflection.getField(objectWithField.getClass(), fieldType, objectWithField);
   }

   /**
    * Gets the value of a non-accessible static field defined in a given class.
    *
    * @param classWithStaticField the class from which to get the field value
    * @param fieldName the name of the static field to get
    * @param  interface or class type to which the returned value should be assignable
    *
    * @throws IllegalArgumentException if the desired field is not found
    *
    * @see #getField(Class, Class)
    * @see #getField(Object, String)
    * @see #setField(Class, String, Object)
    */
   public static  T getField(Class classWithStaticField, String fieldName) {
      return FieldReflection.getField(classWithStaticField, fieldName, null);
   }

   /**
    * Gets the value of a non-accessible static field defined in a given class, assuming there is only one
    * field declared in the given class whose type can receive values of the specified field type.
    *
    * @param classWithStaticField the class from which to get the field value
    * @param fieldType the declared type of the field, or a sub-type of the declared field type
    * @param  interface or class type to which the returned value should be assignable
    *
    * @throws IllegalArgumentException if either the desired field is not found, or more than one is
    *
    * @see #getField(Class, String)
    * @see #getField(Object, Class)
    * @see #setField(Class, Object)
    */
   public static  T getField(Class classWithStaticField, Class fieldType) {
      return FieldReflection.getField(classWithStaticField, fieldType, null);
   }

   /**
    * Sets the value of a non-accessible field on a given object.
    *
    * @param objectWithField the instance on which to set the field value
    * @param fieldName the name of the field to set
    * @param fieldValue the value to set the field to
    *
    * @throws IllegalArgumentException if the desired field is not found
    *
    * @see #setField(Class, String, Object)
    * @see #setField(Object, Object)
    * @see #getField(Object, String)
    */
   public static void setField(Object objectWithField, String fieldName, Object fieldValue) {
      FieldReflection.setField(objectWithField.getClass(), objectWithField, fieldName, fieldValue);
   }

   /**
    * Sets the value of a non-accessible field on a given object.
    * The field is looked up by the type of the given field value instead of by name.
    *
    * @throws IllegalArgumentException if either the desired field is not found, or more than one is
    *
    * @see #setField(Object, String, Object)
    * @see #setField(Class, String, Object)
    * @see #getField(Object, String)
    */
   public static void setField(Object objectWithField, Object fieldValue) {
      FieldReflection.setField(objectWithField.getClass(), objectWithField, null, fieldValue);
   }

   /**
    * Sets the value of a non-accessible static field on a given class.
    *
    * @param classWithStaticField the class on which the static field is defined
    * @param fieldName the name of the field to set
    * @param fieldValue the value to set the field to
    *
    * @throws IllegalArgumentException if the desired field is not found
    *
    * @see #setField(Class, Object)
    * @see #setField(Object, String, Object)
    * @see #getField(Class, String)
    */
   public static void setField(Class classWithStaticField, String fieldName, Object fieldValue) {
      FieldReflection.setField(classWithStaticField, null, fieldName, fieldValue);
   }

   /**
    * Sets the value of a non-accessible static field on a given class.
    * The field is looked up by the type of the given field value instead of by name.
    *
    * @param classWithStaticField the class on which the static field is defined
    * @param fieldValue the value to set the field to
    *
    * @throws IllegalArgumentException if either the desired field is not found, or more than one is
    *
    * @see #setField(Class, String, Object)
    * @see #setField(Object, Object)
    * @see #getField(Class, Class)
    */
   public static void setField(Class classWithStaticField, Object fieldValue) {
      FieldReflection.setField(classWithStaticField, null, null, fieldValue);
   }

   /**
    * Creates a new instance of a given class, without invoking any constructor.
    * If the given class is abstract or an interface, then a concrete class is created, with empty
    * implementations for the abstract/interface methods.
    *
    * @param classToInstantiate the class to be instantiated
    * @param  type to which the returned instance should be assignable
    *
    * @return a newly created instance of the specified class, with any instance fields left uninitialized
    */
   public static  T newUninitializedInstance(Class classToInstantiate) {
      if (classToInstantiate.isInterface()) {
         T instance = Impl.newEmptyProxy(classToInstantiate.getClassLoader(), classToInstantiate);
         return instance;
      }

      if (isAbstract(classToInstantiate.getModifiers())) {
         classToInstantiate = new ConcreteSubclass(classToInstantiate).generateClass();
      }

      return ConstructorReflection.newUninitializedInstance(classToInstantiate);
   }
}