CachingDestinationResolverProxy for slow target DestinationResolvers

Issue: SPR-11939

spring-messaging/src/test/java/org/springframework/messaging/core/CachingDestinationResolverTests.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2002-2014 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.messaging.core;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+/**
+ * Unit tests for {@link CachingDestinationResolverProxy}.
+ *
+ * @author Agim Emruli
+ * @author Juergen Hoeller
+ */
+public class CachingDestinationResolverTests {
+
+    @Test
+    public void cachedDestination() {
+        @SuppressWarnings("unchecked")
+        DestinationResolver<String> destinationResolver = (DestinationResolver<String>) mock(DestinationResolver.class);
+        CachingDestinationResolverProxy<String> cachingDestinationResolver = new CachingDestinationResolverProxy<String>(destinationResolver);
+
+        when(destinationResolver.resolveDestination("abcd")).thenReturn("dcba");
+		when(destinationResolver.resolveDestination("1234")).thenReturn("4321");
+
+        assertEquals("dcba", cachingDestinationResolver.resolveDestination("abcd"));
+        assertEquals("4321", cachingDestinationResolver.resolveDestination("1234"));
+		assertEquals("4321", cachingDestinationResolver.resolveDestination("1234"));
+		assertEquals("dcba", cachingDestinationResolver.resolveDestination("abcd"));
+
+        verify(destinationResolver, times(1)).resolveDestination("abcd");
+		verify(destinationResolver, times(1)).resolveDestination("1234");
+    }
+
+	@Test(expected = IllegalArgumentException.class)
+	public void noTargetSet() {
+		CachingDestinationResolverProxy<String> cachingDestinationResolver = new CachingDestinationResolverProxy<String>();
+		cachingDestinationResolver.afterPropertiesSet();
+	}
+
+    @Test(expected = IllegalArgumentException.class)
+    public void nullTargetThroughConstructor() {
+        new CachingDestinationResolverProxy<String>(null);
+    }
+
+}