001/* 002 * Copyright 2002-2018 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.messaging.core; 018 019import java.util.Map; 020import java.util.concurrent.ConcurrentHashMap; 021 022import org.springframework.beans.factory.InitializingBean; 023import org.springframework.lang.Nullable; 024import org.springframework.util.Assert; 025 026/** 027 * {@link DestinationResolver} implementation that proxies a target DestinationResolver, 028 * caching its {@link #resolveDestination} results. Such caching is particularly useful 029 * if the destination resolving process is expensive (e.g. the destination has to be 030 * resolved through an external system) and the resolution results are stable anyway. 031 * 032 * @author Agim Emruli 033 * @author Juergen Hoeller 034 * @since 4.1 035 * @param <D> the destination type 036 * @see DestinationResolver#resolveDestination 037 */ 038public class CachingDestinationResolverProxy<D> implements DestinationResolver<D>, InitializingBean { 039 040 private final Map<String, D> resolvedDestinationCache = new ConcurrentHashMap<>(); 041 042 @Nullable 043 private DestinationResolver<D> targetDestinationResolver; 044 045 046 /** 047 * Create a new CachingDestinationResolverProxy, setting the target DestinationResolver 048 * through the {@link #setTargetDestinationResolver} bean property. 049 */ 050 public CachingDestinationResolverProxy() { 051 } 052 053 /** 054 * Create a new CachingDestinationResolverProxy using the given target 055 * DestinationResolver to actually resolve destinations. 056 * @param targetDestinationResolver the target DestinationResolver to delegate to 057 */ 058 public CachingDestinationResolverProxy(DestinationResolver<D> targetDestinationResolver) { 059 Assert.notNull(targetDestinationResolver, "Target DestinationResolver must not be null"); 060 this.targetDestinationResolver = targetDestinationResolver; 061 } 062 063 064 /** 065 * Set the target DestinationResolver to delegate to. 066 */ 067 public void setTargetDestinationResolver(DestinationResolver<D> targetDestinationResolver) { 068 this.targetDestinationResolver = targetDestinationResolver; 069 } 070 071 @Override 072 public void afterPropertiesSet() { 073 if (this.targetDestinationResolver == null) { 074 throw new IllegalArgumentException("Property 'targetDestinationResolver' is required"); 075 } 076 } 077 078 079 /** 080 * Resolves and caches destinations if successfully resolved by the target 081 * DestinationResolver implementation. 082 * @param name the destination name to be resolved 083 * @return the currently resolved destination or an already cached destination 084 * @throws DestinationResolutionException if the target DestinationResolver 085 * reports an error during destination resolution 086 */ 087 @Override 088 public D resolveDestination(String name) throws DestinationResolutionException { 089 D destination = this.resolvedDestinationCache.get(name); 090 if (destination == null) { 091 Assert.state(this.targetDestinationResolver != null, "No target DestinationResolver set"); 092 destination = this.targetDestinationResolver.resolveDestination(name); 093 this.resolvedDestinationCache.put(name, destination); 094 } 095 return destination; 096 } 097 098}