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Camel JCache support
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.camel.component.jcache.policy;

import java.util.Set;

import javax.cache.Cache;
import javax.cache.CacheManager;
import javax.cache.Caching;
import javax.cache.configuration.Configuration;
import javax.cache.configuration.MutableConfiguration;

import org.apache.camel.Expression;
import org.apache.camel.NamedNode;
import org.apache.camel.Processor;
import org.apache.camel.Route;
import org.apache.camel.spi.Policy;
import org.apache.camel.util.ObjectHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Policy for routes. It caches the final body of a route and next time takes it from the cache instead of executing the
 * route. The cache key is determined by the keyExpression (message body by default). If there is an object in the cache
 * under that key the rest of the route is not executed, but the cached object is added to the Exchange.
 *
 * Fields: cache: JCache to use cacheManager: If cache is not set, a new one is get or created using this cacheManager.
 * If cacheManager is not set, we try to lookup one from CamelContext. cacheName: Name of the cache to use or create.
 * RouteId is used by default. cacheConfiguration: CacheConfiguration used if a new cache is created. Using default
 * MutableConfiguration if not set. keyExpression: The Expression to generate the key for the cache. E.g
 * simple("${header.username}") enabled: If JCachePolicy is not enabled, no policy is added to the route. Has an impact
 * only during startup.
 */
public class JCachePolicy implements Policy {
    private static final Logger LOG = LoggerFactory.getLogger(JCachePolicy.class);

    private Cache cache;
    private CacheManager cacheManager;
    private String cacheName;
    private Configuration cacheConfiguration;
    private Expression keyExpression;
    private Expression bypassExpression;
    private boolean enabled = true;

    @Override
    public void beforeWrap(Route route, NamedNode namedNode) {
        // noop
    }

    @Override
    public Processor wrap(Route route, Processor processor) {
        //Don't add JCachePolicyProcessor if JCachePolicy is disabled. This means enable/disable has impact only during startup
        if (!isEnabled()) {
            return processor;
        }

        Cache cache = this.cache;
        if (cache == null) {
            //Create cache based on given configuration

            //Find CacheManager
            CacheManager cacheManager = this.cacheManager;

            //Lookup CacheManager from CamelContext if it's not set
            if (cacheManager == null) {
                Set lookupResult = route.getCamelContext().getRegistry().findByType(CacheManager.class);
                if (ObjectHelper.isNotEmpty(lookupResult)) {

                    //Use the first cache manager found
                    cacheManager = lookupResult.iterator().next();
                    LOG.debug("CacheManager from CamelContext registry: {}", cacheManager);
                }
            }

            //Lookup CacheManager the standard way
            if (cacheManager == null) {
                cacheManager = Caching.getCachingProvider().getCacheManager();
                LOG.debug("CacheManager from CachingProvider: {}", cacheManager);
            }

            //Use routeId as cacheName if it's not set
            String cacheName = ObjectHelper.isNotEmpty(this.cacheName) ? this.cacheName : route.getRouteId();
            LOG.debug("Getting cache:{}", cacheName);

            //Get cache or create a new one using the cacheConfiguration
            cache = cacheManager.getCache(cacheName);
            if (cache == null) {
                LOG.debug("Create cache:{}", cacheName);
                cache = cacheManager.createCache(cacheName,
                        cacheConfiguration != null ? this.cacheConfiguration : (Configuration) new MutableConfiguration());
            }

        }

        return new JCachePolicyProcessor(route.getCamelContext(), cache, keyExpression, bypassExpression, processor);
    }

    public Cache getCache() {
        return cache;
    }

    public void setCache(Cache cache) {
        this.cache = cache;
    }

    public CacheManager getCacheManager() {
        return cacheManager;
    }

    public void setCacheManager(CacheManager cacheManager) {
        this.cacheManager = cacheManager;
    }

    public Configuration getCacheConfiguration() {
        return cacheConfiguration;
    }

    public void setCacheConfiguration(Configuration cacheConfiguration) {
        this.cacheConfiguration = cacheConfiguration;
    }

    public String getCacheName() {
        return cacheName;
    }

    public void setCacheName(String cacheName) {
        this.cacheName = cacheName;
    }

    public Expression getKeyExpression() {
        return keyExpression;
    }

    public void setKeyExpression(Expression keyExpression) {
        this.keyExpression = keyExpression;
    }

    public Expression getBypassExpression() {
        return bypassExpression;
    }

    public void setBypassExpression(Expression bypassExpression) {
        this.bypassExpression = bypassExpression;
    }

    public boolean isEnabled() {
        return enabled;
    }

    public void setEnabled(boolean enabled) {
        this.enabled = enabled;
    }

    @Override
    public String toString() {
        return "JCachePolicy{"
               + "keyExpression=" + keyExpression
               + ", enabled=" + enabled
               + '}';
    }
}