CacheableRequestPolicy.java

/*
 * ====================================================================
 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */
package com.apigee.sdk.apm.http.impl.client.cache;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.http.Header;
import org.apache.http.HeaderElement;
import org.apache.http.HttpRequest;
import org.apache.http.HttpVersion;
import org.apache.http.ProtocolVersion;

import com.apigee.sdk.apm.http.annotation.Immutable;
import com.apigee.sdk.apm.http.client.cache.HeaderConstants;

/**
 * Determines if an HttpRequest is allowed to be served from the cache.
 * 
 * @since 4.1
 */
@Immutable
class CacheableRequestPolicy {

	private final Log log = LogFactory.getLog(getClass());

	/**
	 * Determines if an HttpRequest can be served from the cache.
	 * 
	 * @param request
	 *            an HttpRequest
	 * @return boolean Is it possible to serve this request from cache
	 */
	public boolean isServableFromCache(HttpRequest request) {
		String method = request.getRequestLine().getMethod();

		ProtocolVersion pv = request.getRequestLine().getProtocolVersion();
		if (HttpVersion.HTTP_1_1.compareToVersion(pv) != 0) {
			log.debug("Request was not serveable from cache");
			return false;
		}

		if (!method.equals(HeaderConstants.GET_METHOD)) {
			log.debug("Request was not serveable from cache");
			return false;
		}

		if (request.getHeaders(HeaderConstants.PRAGMA).length > 0) {
			log.debug("Request was not serveable from cache");
			return false;
		}

		Header[] cacheControlHeaders = request
				.getHeaders(HeaderConstants.CACHE_CONTROL);
		for (Header cacheControl : cacheControlHeaders) {
			for (HeaderElement cacheControlElement : cacheControl.getElements()) {
				if (HeaderConstants.CACHE_CONTROL_NO_STORE
						.equalsIgnoreCase(cacheControlElement.getName())) {
					log.debug("Request was not serveable from Cache");
					return false;
				}

				if (HeaderConstants.CACHE_CONTROL_NO_CACHE
						.equalsIgnoreCase(cacheControlElement.getName())) {
					log.debug("Request was not serveable from cache");
					return false;
				}
			}
		}

		log.debug("Request was serveable from cache");
		return true;
	}

}