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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.internal.reflection;

import java.lang.reflect.*;
import java.util.*;
import javax.annotation.*;

/**
 * This marker interface exists only to guarantee that JMockit can get the bytecode definition of
 * each Proxy class it creates through java.lang.reflect.Proxy.
 * If such a class is created before JMockit is initialized, its bytecode won't be stored in
 * JMockit's cache. And since the JDK uses an internal cache for proxy classes, it won't create a
 * new one, therefore not going through the ProxyRegistrationTransformer. So, by always implementing
 * this additional interface, we can guarantee a new proxy class will be created when JMockit first
 * requests it for a given interface.
 */
public interface EmptyProxy
{
   final class Impl {
      private Impl() {}

      @Nonnull
      public static  E newEmptyProxy(@Nullable ClassLoader loader, @Nonnull Type... interfacesToBeProxied) {
         List> interfaces = new ArrayList<>();

         for (Type type : interfacesToBeProxied) {
            addInterface(interfaces, type);
         }

         if (loader == null) {
            //noinspection AssignmentToMethodParameter
            loader = interfaces.get(0).getClassLoader();
         }

         if (loader == EmptyProxy.class.getClassLoader()) {
            interfaces.add(EmptyProxy.class);
         }

         Class[] interfacesArray = interfaces.toArray(new Class[interfaces.size()]);

         //noinspection unchecked
         return (E) Proxy.newProxyInstance(loader, interfacesArray, MockInvocationHandler.INSTANCE);
      }

      private static void addInterface(@Nonnull List> interfaces, @Nonnull Type type) {
         if (type instanceof Class) {
            interfaces.add((Class) type);
         }
         else if (type instanceof ParameterizedType) {
            ParameterizedType paramType = (ParameterizedType) type;
            interfaces.add((Class) paramType.getRawType());
         }
         else if (type instanceof TypeVariable) {
            TypeVariable typeVar = (TypeVariable) type;
            addBoundInterfaces(interfaces, typeVar.getBounds());
         }
      }

      private static void addBoundInterfaces(@Nonnull List> interfaces, @Nonnull Type[] bounds) {
         for (Type bound : bounds) {
            addInterface(interfaces, bound);
         }
      }
   }
}