Introduce ReflectionUtils#getUniqueDeclaredMethods

This change is in support of certain polymorphism cases in
@Configuration class inheritance hierarchies.  Consider the following
scenario:

@Configuration
public abstract class AbstractConfig {
    public abstract Object bean();
}

@Configuration
public class ConcreteConfig {
    @Override
    @Bean
    public BeanPostProcessor bean() { ... }
}

ConcreteConfig overrides AbstractConfig's #bean() method with a
covariant return type, in this case returning an object of type
BeanPostProcessor.  It is critically important that the container
is able to detect the return type of ConcreteConfig#bean() in order
to instantiate the BPP at the right point in the lifecycle.

Prior to this change, the container could not do this.
AbstractAutowireCapableBeanFactory#getTypeForFactoryMethod called
ReflectionUtils#getAllDeclaredMethods, which returned Method objects
for both the Object and BeanPostProcessor signatures of the #bean()
method.  This confused the implementation sufficiently as not to
choose a type for the factory method at all.  This means that the
BPP never gets detected as a BPP.

The new method being introduced here, #getUniqueDeclaredMethods, takes
covariant return types into account, and filters out duplicates,
favoring the most specific / narrow return type.

Additionally, it filters out any CGLIB 'rewritten' methods, which
is important in the case of @Configuration classes, which are
enhanced by CGLIB.  See the implementation for further details.

org.springframework.context/src/test/java/org/springframework/context/annotation/ReflectionUtilsIntegrationTests.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2002-2011 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.context.annotation;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+
+import java.lang.reflect.Method;
+
+import org.junit.Test;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * Tests ReflectionUtils methods as used against CGLIB-generated classes created
+ * by ConfigurationClassEnhancer.
+ *
+ * @author Chris Beams
+ * @since 3.1
+ * @see org.springframework.util.ReflectionUtilsTests
+ */
+public class ReflectionUtilsIntegrationTests {
+
+	@Test
+	public void getUniqueDeclaredMethods_withCovariantReturnType_andCglibRewrittenMethodNames() throws Exception {
+		DefaultListableBeanFactory bf = new DefaultListableBeanFactory();
+		Class<?> cglibLeaf = new ConfigurationClassEnhancer(bf).enhance(Leaf.class);
+		int m1MethodCount = 0;
+		Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(cglibLeaf);
+		for (Method method : methods) {
+			if (method.getName().equals("m1")) {
+				m1MethodCount++;
+			}
+		}
+		assertThat(m1MethodCount, is(1));
+		for (Method method : methods) {
+			if (method.getName().contains("m1")) {
+				assertEquals(method.getReturnType(), Integer.class);
+			}
+		}
+	}
+
+
+	@Configuration
+	static abstract class Parent {
+		public abstract Number m1();
+	}
+
+
+	@Configuration
+	static class Leaf extends Parent {
+		@Override
+		@Bean
+		public Integer m1() {
+			return new Integer(42);
+		}
+	}
+
+}