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Camel Cache support based on ehCache
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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.cache;

import java.io.InputStream;
import java.io.Serializable;
import java.util.Map;

import net.sf.ehcache.CacheException;
import net.sf.ehcache.Ehcache;
import net.sf.ehcache.Element;

import org.apache.camel.Exchange;
import org.apache.camel.NoTypeConversionAvailableException;
import org.apache.camel.impl.DefaultProducer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class CacheProducer extends DefaultProducer {
    private static final Logger LOG = LoggerFactory.getLogger(CacheProducer.class);
    private CacheConfiguration config;
    private Ehcache cache;

    public CacheProducer(CacheEndpoint endpoint, CacheConfiguration config) throws Exception {
        super(endpoint);
        this.config = config;
    }

    @Override
    protected void doStart() throws Exception {
        super.doStart();
        cache = getEndpoint().initializeCache();
    }

    @Override
    public CacheEndpoint getEndpoint() {
        return (CacheEndpoint) super.getEndpoint();
    }

    public void process(Exchange exchange) throws Exception {
        LOG.trace("Cache Name: {}", config.getCacheName());
        Map headers = exchange.getIn().getHeaders();
        String key = (headers.containsKey(CacheConstants.CACHE_KEY))
                ? exchange.getIn().getHeader(CacheConstants.CACHE_KEY, String.class)
                : getEndpoint().getKey();

        String operation = (headers.containsKey(CacheConstants.CACHE_OPERATION)) ? (String)headers
                .get(CacheConstants.CACHE_OPERATION) : getEndpoint().getOperation();

        if (operation == null) {
            throw new CacheException(CacheConstants.CACHE_OPERATION + " header not specified in message");
        }
        if ((key == null) && (!checkIsEqual(operation, CacheConstants.CACHE_OPERATION_DELETEALL))) {
            throw new CacheException(CacheConstants.CACHE_KEY + " is not specified in message header or endpoint URL.");
        }

        performCacheOperation(exchange, operation, key);

        //cleanup the cache headers
        exchange.getIn().removeHeader(CacheConstants.CACHE_KEY);
        exchange.getIn().removeHeader(CacheConstants.CACHE_OPERATION);
    }

    private void performCacheOperation(Exchange exchange, String operation, String key) throws Exception {

        if (checkIsEqual(operation, CacheConstants.CACHE_OPERATION_URL_ADD)) {
            LOG.debug("Adding an element with key {} into the Cache", key);
            Element element = createElementFromBody(key, exchange, CacheConstants.CACHE_OPERATION_ADD);
            cache.put(element);
        } else if (checkIsEqual(operation, CacheConstants.CACHE_OPERATION_URL_UPDATE)) {
            LOG.debug("Updating an element with key {} into the Cache", key);
            Element element = createElementFromBody(key, exchange, CacheConstants.CACHE_OPERATION_UPDATE);
            cache.put(element);
        } else if (checkIsEqual(operation, CacheConstants.CACHE_OPERATION_URL_DELETEALL)) {
            LOG.debug("Deleting All elements from the Cache");
            cache.removeAll();
        } else if (checkIsEqual(operation, CacheConstants.CACHE_OPERATION_URL_DELETE)) {
            LOG.debug("Deleting an element with key {} into the Cache", key);
            cache.remove(key);
        } else if (checkIsEqual(operation, CacheConstants.CACHE_OPERATION_URL_GET)) {
            LOG.debug("Quering an element with key {} from the Cache", key);
            if (cache.get(key) != null) {
                exchange.getIn().setHeader(CacheConstants.CACHE_ELEMENT_WAS_FOUND, true);
                exchange.getIn().setBody(cache.get(key).getObjectValue());
            } else {
                exchange.getIn().removeHeader(CacheConstants.CACHE_ELEMENT_WAS_FOUND);
            }
        } else if (checkIsEqual(operation, CacheConstants.CACHE_OPERATION_URL_CHECK)) {
            LOG.debug("Querying an element with key {} from the Cache", key);
            Element element = cache.getQuiet(key); // getQuiet checks for element expiry
            if (element != null) {
                exchange.getIn().setHeader(CacheConstants.CACHE_ELEMENT_WAS_FOUND, true);
            } else {
                exchange.getIn().removeHeader(CacheConstants.CACHE_ELEMENT_WAS_FOUND);
            }
        } else {
            throw new CacheException(CacheConstants.CACHE_OPERATION + " " + operation + " is not supported.");
        }
    }

    private boolean checkIsEqual(String operation, String constant) {
        return operation.equalsIgnoreCase(constant)
                || operation.equalsIgnoreCase(CacheConstants.CACHE_HEADER_PREFIX + constant);
    }


    private Element createElementFromBody(String key, Exchange exchange, String cacheOperation) throws NoTypeConversionAvailableException {
        Element element;
        Object body = exchange.getIn().getBody();
        if (body == null) {
            throw new CacheException("Body cannot be null for operation " + cacheOperation);
        } else if (body instanceof Serializable) {
            element = new Element(key, body);
        } else {
            InputStream is = exchange.getContext().getTypeConverter().mandatoryConvertTo(InputStream.class, body);
            // Read InputStream into a byte[] buffer
            element = new Element(key, exchange.getContext().getTypeConverter().mandatoryConvertTo(byte[].class, is));
        }
        // set overrides for the cache expiration and such
        final Integer ttl = exchange.getIn().getHeader(CacheConstants.CACHE_ELEMENT_EXPIRY_TTL, Integer.class);
        if (ttl != null) {
            element.setTimeToLive(ttl);
        }
        final Integer idle = exchange.getIn().getHeader(CacheConstants.CACHE_ELEMENT_EXPIRY_IDLE, Integer.class);
        if (idle != null) {
            element.setTimeToIdle(idle);
        }
        final Boolean flag = exchange.getIn().getHeader(CacheConstants.CACHE_ELEMENT_EXPIRY_ETERNAL, Boolean.class);
        if (flag != null) {
            element.setEternal(flag);
        }

        return element;
    }

}