concepts/src/main/java/org/opendaylight/yangtools/concepts/util/ClassLoaderUtils.java

   1 /*
   2  * Copyright (c) 2013 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.yangtools.concepts.util;
   9
  10 import java.lang.reflect.ParameterizedType;
  11 import java.lang.reflect.Type;
  12 import java.util.concurrent.Callable;
  13 import java.util.concurrent.locks.Lock;
  14
  15
  16 public final class ClassLoaderUtils {
  17
  18     private ClassLoaderUtils() {
  19         throw new UnsupportedOperationException("Utility class");
  20     }
  21
  22     public static <V> V withClassLoader(ClassLoader cls, Callable<V> function) throws Exception {
  23         return withClassLoaderAndLock(cls, null, function);
  24     }
  25
  26     public static <V> V withClassLoaderAndLock(ClassLoader cls, Lock lock, Callable<V> function) throws Exception {
  27         if (cls == null) {
  28             throw new IllegalArgumentException("Classloader should not be null");
  29         }
  30         if (function == null) {
  31             throw new IllegalArgumentException("Function should not be null");
  32         }
  33
  34         if (lock != null) {
  35             lock.lock();
  36         }
  37         ClassLoader oldCls = Thread.currentThread().getContextClassLoader();
  38         try {
  39             Thread.currentThread().setContextClassLoader(cls);
  40             return function.call();
  41         } finally {
  42             Thread.currentThread().setContextClassLoader(oldCls);
  43             if (lock != null) {
  44                 lock.unlock();
  45             }
  46         }
  47     }
  48
  49     public static ParameterizedType findParameterizedType(Class<?> subclass, Class<?> genericType) {
  50         if(subclass == null || genericType == null) {
  51             throw new IllegalArgumentException("Class was not specified.");
  52         }
  53         for (Type type : subclass.getGenericInterfaces()) {
  54             if (type instanceof ParameterizedType && genericType.equals(((ParameterizedType) type).getRawType())) {
  55                 return (ParameterizedType) type;
  56             }
  57         }
  58         return null;
  59     }
  60
  61     public static <S,G,P> Class<P> findFirstGenericArgument(final Class<S> scannedClass, final Class<G> genericType) {
  62         try {
  63             return withClassLoader(scannedClass.getClassLoader(), ClassLoaderUtils.<S,G,P>findFirstGenericArgumentTask(scannedClass, genericType));
  64         } catch (Exception e) {
  65             return null;
  66         }
  67     }
  68
  69     private static <S,G,P> Callable<Class<P>> findFirstGenericArgumentTask(final Class<S> scannedClass, final Class<G> genericType) {
  70         return new Callable<Class<P>>() {
  71             @Override
  72             @SuppressWarnings("unchecked")
  73             public Class<P> call() throws Exception {
  74                 final ParameterizedType augmentationGeneric = findParameterizedType(scannedClass,
  75                         genericType);
  76                 if (augmentationGeneric == null) {
  77                     return null;
  78                 }
  79                 return (Class<P>) augmentationGeneric.getActualTypeArguments()[0];
  80             }
  81         };
  82     }
  83
  84     public static Type getFirstGenericParameter(Type type) {
  85         if(type instanceof ParameterizedType) {
  86             return ((ParameterizedType) type).getActualTypeArguments()[0];
  87         }
  88         return null;
  89     }
  90
  91 }