DATACMNS-1324 - Introduced extensible proxy detection infrastructure.

Introduced ProxyUtils.getUserClass(…) that by default is basically a facade for Spring's ClassUtils.getUserClass(…) but allows the registration of ProxyDetector implementations via Spring's SpringFactoriesLoader mechanism.

Moved all existing usages of ClassUtils.getUserClass(…) to ProxyUtils.

src/main/java/org/springframework/data/util/ClassTypeInformation.java

@@ -89,7 +89,7 @@ public class ClassTypeInformation<S> extends TypeDiscoverer<S> {
 	 * @param type
 	 */
 	ClassTypeInformation(Class<S> type) {
-		super(ClassUtils.getUserClass(type), getTypeVariableMap(type));
+		super(ProxyUtils.getUserClass(type), getTypeVariableMap(type));
 		this.type = type;
 	}
 

src/main/java/org/springframework/data/util/ProxyUtils.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed 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.springframework.data.util;
+
+import lombok.experimental.UtilityClass;
+
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.core.io.support.SpringFactoriesLoader;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ConcurrentReferenceHashMap;
+
+/**
+ * Proxy type detection utilities, extensible via {@link ProxyDetector} registered via Spring factories.
+ * 
+ * @author Oliver Gierke
+ * @soundtrack Victor Wooten - Cruising Altitude (Trypnotix)
+ */
+@UtilityClass
+public class ProxyUtils {
+
+	private static Map<Class<?>, Class<?>> USER_TYPES = new ConcurrentReferenceHashMap<>();
+
+	private static final List<ProxyDetector> DETECTORS = SpringFactoriesLoader.loadFactories(ProxyDetector.class,
+			ProxyUtils.class.getClassLoader());
+
+	static {
+		DETECTORS.add(ClassUtils::getUserClass);
+	}
+
+	/**
+	 * Returns the user class for the given type.
+	 * 
+	 * @param type must not be {@literal null}.
+	 * @return
+	 */
+	public static Class<?> getUserClass(Class<?> type) {
+
+		Assert.notNull(type, "Type must not be null!");
+
+		return USER_TYPES.computeIfAbsent(type, it -> {
+
+			Class<?> result = it;
+
+			for (ProxyDetector proxyDetector : DETECTORS) {
+				result = proxyDetector.getUserType(result);
+			}
+
+			return result;
+		});
+	}
+
+	/**
+	 * Returns the user class for the given source object.
+	 * 
+	 * @param source must not be {@literal null}.
+	 * @return
+	 */
+	public static Class<?> getUserClass(Object source) {
+
+		Assert.notNull(source, "Source object must not be null!");
+
+		return getUserClass(source.getClass());
+	}
+
+	/**
+	 * SPI to extend Spring's default proxy detection capabilities.
+	 *
+	 * @author Oliver Gierke
+	 */
+	public interface ProxyDetector {
+
+		/**
+		 * Returns the user class for the given type.
+		 * 
+		 * @param type will never be {@literal null}.
+		 * @return
+		 */
+		Class<?> getUserType(Class<?> type);
+	}
+}