Distinguish between different bridge method types

Add BridgeMethodResolver#isJava6VisibilityBridgeMethodPair to
distinguish between (a) bridge methods introduced in Java 6 to
compensate for inheriting public methods from non-public superclasses
and (b) bridge methods that have existed since Java 5 to accommodate
return type covariance and generic parameters.

In the former case, annotations should be looked up from the original
bridged method (SPR-7900).  In the latter, the annotation should be
looked up against the bridge method itself (SPR-8660).

As noted in the Javadoc for the new method, see
http://stas-blogspot.blogspot.com/2010/03/java-bridge-methods-explained.html
for a useful description of the various types of bridge methods, as
well as http://bugs.sun.com/view_bug.do?bug_id=6342411, the bug fixed in
Java 6 resulting in the introduction of 'visibility bridge methods'.

Issue: SPR-8660, SPR-7900

org.springframework.core/src/main/java/org/springframework/core/BridgeMethodResolver.java

@@ -25,6 +25,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ReflectionUtils;
 
@@ -210,4 +211,22 @@ public abstract class BridgeMethodResolver {
 		return ReflectionUtils.findMethod(type, bridgeMethod.getName(), bridgeMethod.getParameterTypes());
 	}
 
+	/**
+	 * Compare the signatures of the bridge method and the method which it bridges. If
+	 * the parameter and return types are the same, it is a 'visibility' bridge method
+	 * introduced in Java 6 to fix http://bugs.sun.com/view_bug.do?bug_id=6342411.
+	 * See also http://stas-blogspot.blogspot.com/2010/03/java-bridge-methods-explained.html
+	 * @return whether signatures match as described
+	 */
+	public static boolean isJava6VisibilityBridgeMethodPair(Method bridgeMethod, Method bridgedMethod) {
+		Assert.isTrue(bridgeMethod != null);
+		Assert.isTrue(bridgedMethod != null);
+		if (bridgeMethod == bridgedMethod) {
+			return true;
+		}
+		return Arrays.equals(bridgeMethod.getParameterTypes(), bridgedMethod.getParameterTypes())
+				&& bridgeMethod.getReturnType().equals(bridgedMethod.getReturnType());
+	}
+
+
 }