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 static org.opendaylight.yangtools.concepts.util.ClassLoaderUtils.findParameterizedType;
  11
  12 import java.lang.reflect.ParameterizedType;
  13 import java.lang.reflect.Type;
  14 import java.util.concurrent.Callable;
  15 import java.util.concurrent.locks.Lock;
  16
  17
  18 public final class ClassLoaderUtils {
  19
  20     private ClassLoaderUtils() {
  21         throw new UnsupportedOperationException("Utility class");
  22     }
  23
  24     public static <V> V withClassLoader(ClassLoader cls, Callable<V> function) throws Exception {
  25         return withClassLoaderAndLock(cls, null, function);
  26     }
  27
  28     public static <V> V withClassLoaderAndLock(ClassLoader cls, Lock lock, Callable<V> function) throws Exception {
  29         if (cls == null) {
  30             throw new IllegalArgumentException("Classloader should not be null");
  31         }
  32         if (function == null) {
  33             throw new IllegalArgumentException("Function should not be null");
  34         }
  35
  36         if (lock != null) {
  37             lock.lock();
  38         }
  39         ClassLoader oldCls = Thread.currentThread().getContextClassLoader();
  40         try {
  41             Thread.currentThread().setContextClassLoader(cls);
  42             return function.call();
  43         } finally {
  44             Thread.currentThread().setContextClassLoader(oldCls);
  45             if (lock != null) {
  46                 lock.unlock();
  47             }
  48         }
  49     }
  50
  51     public static ParameterizedType findParameterizedType(Class<?> subclass, Class<?> genericType) {
  52         if(subclass == null || genericType == null) {
  53             throw new IllegalArgumentException("Class was not specified.");
  54         }
  55         for (Type type : subclass.getGenericInterfaces()) {
  56             if (type instanceof ParameterizedType && genericType.equals(((ParameterizedType) type).getRawType())) {
  57                 return (ParameterizedType) type;
  58             }
  59         }
  60         return null;
  61     }
  62
  63     public static <S,G,P> Class<P> findFirstGenericArgument(final Class<S> scannedClass, final Class<G> genericType) {
  64         try {
  65             return withClassLoader(scannedClass.getClassLoader(), ClassLoaderUtils.<S,G,P>findFirstGenericArgumentTask(scannedClass, genericType));
  66         } catch (Exception e) {
  67             return null;
  68         }
  69     }
  70
  71     private static <S,G,P> Callable<Class<P>> findFirstGenericArgumentTask(final Class<S> scannedClass, final Class<G> genericType) {
  72         return new Callable<Class<P>>() {
  73             @Override
  74             @SuppressWarnings("unchecked")
  75             public Class<P> call() throws Exception {
  76                 final ParameterizedType augmentationGeneric = findParameterizedType(scannedClass,
  77                         genericType);
  78                 if (augmentationGeneric == null) {
  79                     return null;
  80                 }
  81                 return (Class<P>) augmentationGeneric.getActualTypeArguments()[0];
  82             }
  83         };
  84     }
  85
  86     public static Type getFirstGenericParameter(Type type) {
  87         if(type instanceof ParameterizedType) {
  88             return ((ParameterizedType) type).getActualTypeArguments()[0];
  89         }
  90         return null;
  91     }
  92
  93 }