CachingDestinationResolverProxy for slow target DestinationResolvers

Issue: SPR-11939

spring-messaging/src/main/java/org/springframework/messaging/core/CachingDestinationResolverProxy.java

@@ -0,0 +1,94 @@
+/*
+ * 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 java.util.concurrent.ConcurrentHashMap;
+
+import org.springframework.beans.factory.InitializingBean;
+import org.springframework.util.Assert;
+
+/**
+ * {@link DestinationResolver} implementation that proxies a target DestinationResolver,
+ * caching its {@link #resolveDestination} results. Such caching is particularly useful
+ * if the destination resolving process is expensive (e.g. the destination has to be
+ * resolved through an external system) and the resolution results are stable anyway.
+ *
+ * @author Agim Emruli
+ * @author Juergen Hoeller
+ * @since 4.1
+ * @see DestinationResolver#resolveDestination
+ */
+public class CachingDestinationResolverProxy<D> implements DestinationResolver<D>, InitializingBean {
+
+    private final ConcurrentHashMap<String, D> resolvedDestinationCache = new ConcurrentHashMap<String, D>();
+
+    private DestinationResolver<D> targetDestinationResolver;
+
+
+	/**
+	 * Create a new CachingDestinationResolverProxy, setting the target DestinationResolver
+	 * through the {@link #setTargetDestinationResolver} bean property.
+	 */
+	public CachingDestinationResolverProxy() {
+	}
+
+	/**
+     * Create a new CachingDestinationResolverProxy using the given target
+	 * DestinationResolver to actually resolve destinations.
+     * @param targetDestinationResolver the target DestinationResolver to delegate to
+     */
+    public CachingDestinationResolverProxy(DestinationResolver<D> targetDestinationResolver) {
+        Assert.notNull(targetDestinationResolver, "Target DestinationResolver must not be null");
+        this.targetDestinationResolver = targetDestinationResolver;
+    }
+
+
+	/**
+	 * Set the target DestinationResolver to delegate to.
+	 */
+	public void setTargetDestinationResolver(DestinationResolver<D> targetDestinationResolver) {
+		this.targetDestinationResolver = targetDestinationResolver;
+	}
+
+	@Override
+	public void afterPropertiesSet() {
+		if (this.targetDestinationResolver == null) {
+			throw new IllegalArgumentException("Property 'targetDestinationResolver' is required");
+		}
+	}
+
+
+	/**
+     *
+     * Resolves and caches destinations if successfully resolved by the target
+     * DestinationResolver implementation.
+     * @param name the destination name to be resolved
+     * @return the currently resolved destination or an already cached destination
+     * @throws DestinationResolutionException if the target DestinationResolver
+     * reports an error during destination resolution
+     */
+    @Override
+    public D resolveDestination(String name) throws DestinationResolutionException {
+        D destination = this.resolvedDestinationCache.get(name);
+		if (destination == null) {
+            destination = this.targetDestinationResolver.resolveDestination(name);
+			this.resolvedDestinationCache.putIfAbsent(name, destination);
+        }
+        return destination;
+    }
+
+}