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/test/java/org/springframework/data/util/ProxyUtilsUnitTests.java

@@ -0,0 +1,70 @@
+/*
+ * 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 static org.assertj.core.api.Assertions.*;
+
+import org.junit.Test;
+import org.springframework.aop.framework.ProxyFactory;
+import org.springframework.data.util.ProxyUtils.ProxyDetector;
+
+/**
+ * Unit tests for {@link ProxyUtils}.
+ * 
+ * @author Oliver Gierke
+ * @soundtrack Victor Wooten - The 13th Floor (Trypnotix)
+ */
+public class ProxyUtilsUnitTests {
+
+	@Test // DATACMNS-1324
+	public void detectsStandardProxy() {
+
+		ProxyFactory factory = new ProxyFactory();
+		factory.setTarget(new Sample());
+		Object proxy = factory.getProxy();
+
+		assertThat(proxy.getClass()).isNotEqualTo(Sample.class);
+		assertThat(ProxyUtils.getUserClass(proxy)).isEqualTo(Sample.class);
+	}
+
+	@Test // DATACMNS-1324
+	public void usesCustomProxyDetector() {
+
+		ProxyFactory factory = new ProxyFactory();
+		factory.setTarget(new AnotherSample());
+		Object proxy = factory.getProxy();
+
+		assertThat(ProxyUtils.getUserClass(proxy)).isEqualTo(UserType.class);
+	}
+
+	static class SampleProxyDetector implements ProxyDetector {
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.util.ProxyUtils.ProxyDetector#getUserType(java.lang.Class)
+		 */
+		@Override
+		public Class<?> getUserType(Class<?> type) {
+			return AnotherSample.class.isAssignableFrom(type) ? UserType.class : type;
+		}
+	}
+
+	static class Sample {}
+
+	static class UserType {}
+
+	static class AnotherSample {}
+}