Http(Async)Client not actually nullable, plus MethodInterceptor nullability

Issue: SPR-15720

spring-context/src/main/java/org/springframework/cache/interceptor/CacheInterceptor.java

@@ -22,6 +22,8 @@ import java.lang.reflect.Method;
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
 
+import org.springframework.lang.Nullable;
+
 /**
  * AOP Alliance MethodInterceptor for declarative cache
  * management using the common Spring caching infrastructure
@@ -42,6 +44,7 @@ import org.aopalliance.intercept.MethodInvocation;
 public class CacheInterceptor extends CacheAspectSupport implements MethodInterceptor, Serializable {
 
 	@Override
+	@Nullable
 	public Object invoke(final MethodInvocation invocation) throws Throwable {
 		Method method = invocation.getMethod();
 

spring-context/src/main/java/org/springframework/ejb/access/AbstractSlsbInvokerInterceptor.java

@@ -187,6 +187,7 @@ public abstract class AbstractSlsbInvokerInterceptor extends JndiObjectLocator
 	 * {@link #invokeInContext}.
 	 */
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		Context ctx = (this.exposeAccessContext ? getJndiTemplate().getContext() : null);
 		try {

spring-context/src/main/java/org/springframework/jmx/access/MBeanClientInterceptor.java

@@ -354,6 +354,7 @@ public class MBeanClientInterceptor
 	 * @see #handleConnectFailure
 	 */
 	@Override
+	@Nullable
 	public Object invoke(MethodInvocation invocation) throws Throwable {
 		// Lazily connect to MBeanServer if necessary.
 		synchronized (this.preparationMonitor) {