Github user andreaturli commented on a diff in the pull request:
https://github.com/apache/brooklyn-server/pull/808#discussion_r136297846
--- Diff:
core/src/main/java/org/apache/brooklyn/core/objs/proxy/ClassLoaderCache.java ---
@@ -0,0 +1,121 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.brooklyn.core.objs.proxy;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import java.util.Set;
+import java.util.concurrent.ConcurrentMap;
+
+import org.apache.brooklyn.util.javalang.AggregateClassLoader;
+
+import com.google.common.base.Objects;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
+
+/**
+ * For getting/creating {@link AggregateClassLoader} for an entity proxy.
The returned class loader
+ * can be used when calling {@link
java.lang.reflect.Proxy#newProxyInstance(ClassLoader, Class[],
java.lang.reflect.InvocationHandler)}.
+ *
+ * The classloader is created with references to ClassLoaders for the
given class and interfaces
+ * (including all super-classes and super-interfaces of those). Also see
comment in
+ * {@link InternalEntityFactory#createEntityProxy(Iterable,
org.apache.brooklyn.api.entity.Entity)}.
+ *
+ * If a classloader has already been created for the given
class+interfaces, then it guarantees
+ * to return that same classloader instance. This is very important when
using {@code newProxyInstance}
+ * because if a different ClassLoader instance is used then it will
reflectively create a new Proxy class.
+ * See https://issues.apache.org/jira/browse/BROOKLYN-528.
+ */
+class ClassLoaderCache {
--- End diff --
[minor] @aledsage cache looks exactly what we need here.
FYI @robertgmoss has used a `computeIfAbsent` in
https://github.com/apache/brooklyn-server/blob/master/locations/jclouds/src/main/java/org/apache/brooklyn/location/jclouds/AbstractComputeServiceRegistry.java#L79
which may save some boilerplate code.
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