RestCachingManagerImpl.java

/*
 Copyright (c) 2012 GFT Appverse, S.L., Sociedad Unipersonal.

 This Source Code Form is subject to the terms of the Appverse Public License 
 Version 2.0 (“APL v2.0”). If a copy of the APL was not distributed with this 
 file, You can obtain one at http://www.appverse.mobi/licenses/apl_v2.0.pdf. [^]

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 are permitted provided that the conditions of the AppVerse Public License v2.0 
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 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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 DISCLAIMED. EXCEPT IN CASE OF WILLFUL MISCONDUCT OR GROSS NEGLIGENCE, IN NO EVENT
 SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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 */
package org.appverse.web.framework.backend.rest.managers.impl.live;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import javax.ws.rs.RedirectionException;
import javax.ws.rs.client.Invocation.Builder;
import javax.ws.rs.client.WebTarget;
import javax.ws.rs.core.EntityTag;
import javax.ws.rs.core.GenericType;
import javax.ws.rs.core.Response.Status;

import net.sf.ehcache.Cache;
import net.sf.ehcache.CacheManager;
import net.sf.ehcache.Element;

import org.appverse.web.framework.backend.api.helpers.log.AutowiredLogger;
import org.appverse.web.framework.backend.api.model.integration.AbstractIntegrationBean;
import org.appverse.web.framework.backend.rest.annotations.RestCaching;
import org.appverse.web.framework.backend.rest.helpers.cache.CacheEntry;
import org.appverse.web.framework.backend.rest.managers.RestCachingManager;
import org.appverse.web.framework.backend.rest.model.integration.IntegrationPaginatedResult;
import org.appverse.web.framework.backend.rest.services.integration.IRestPersistenceService;
import org.slf4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.annotation.AnnotationUtils;

/**
 * This manager encapsulates the complexity of caching logic.
 * It supports every retrieve method present in RestPersistenceService
 *
 */
public class RestCachingManagerImpl implements RestCachingManager {

	@Autowired
	public CacheManager cacheManager;

	@AutowiredLogger
	private static Logger logger;

	private Object manageRestCaching(final Builder builder, final WebTarget webTarget,
			final Method method,
			final GenericType<?> type,
			final IRestPersistenceService<?> restService, final String key)
			throws Exception
	{
		//Check if caching logic is enabled in repository 
		//(RestCaching annotations could be present in interface OR implementations)

		RestCaching rc = AnnotationUtils.findAnnotation(restService.getClass(), RestCaching.class);
		if (rc != null && key != null)
		{
			String cacheName = rc.cacheName();
			Cache cache = cacheManager.getCache(cacheName);

			if (logger.isDebugEnabled())
				logger.debug("Checking path::" + key);

			Element wrap = cache.get(key);

			//Requested data should be in cache
			if (wrap != null) {
				if (logger.isDebugEnabled())
					logger.debug("Entry in cache is not null...checking expiration date..");
				CacheEntry entry = (CacheEntry) wrap.getObjectValue();
				EntityTag etag = entry.getEtag();
				//Data is cached, so we can return it and avoid to call rest service
				if (!entry.hasExpired() && entry.getObject() != null)
				{
					if (logger.isDebugEnabled())
						logger.debug("Entry has not expired, so returned from cache");

					return entry.getObject();
				}
				//Data is cached, but expired, so remove it
				else if (entry.hasExpired())
				{
					if (logger.isDebugEnabled())
						logger.debug("Entry has expired, do not use it");
				}
				//If we have EntityTag header, send to server to check conditional existence
				if (etag != null && etag.getValue() != null)
				{
					builder.header("If-None-Match", "\"" + etag.getValue() + "\"");
				}

			}

			if (logger.isDebugEnabled())
				logger.debug("Actual call to service");
			//Invoke rest service

			Object data = null;
			boolean notModified = false;
			try
			{
				//Paging methods
				if (webTarget != null)
					data = method.invoke(restService, webTarget, builder);
				//Common retrieve and retrieveList methods
				else
				{

					if (type != null)
						data = method.invoke(builder, type);
					else
						data = method.invoke(builder);
				}
			} catch (InvocationTargetException ite)
			{
				//This could be a NOT_MODIFIED response, produced by server ETAG caching
				//We must check it, and rethrow exception if it's another error
				Throwable target = ite.getTargetException();
				if (target != null && target instanceof RedirectionException)
				{
					RedirectionException re = (RedirectionException) target;
					if (re.getResponse().getStatus() == Status.NOT_MODIFIED.getStatusCode())
					{
						if (logger.isDebugEnabled())
							logger.debug("NOT_MODIFIED response");

						notModified = true;
					}
				}
				if (!notModified)
					throw ite;
			}
			//Jersey RestRequestCachingFilter intercept response from server and analyze headers

			if (logger.isDebugEnabled())
				logger.debug("Checking if we should insert or retrieve data in/from cache");
			wrap = cache.get(key);
			if (wrap != null)
			{
				CacheEntry entry = (CacheEntry) wrap.getObjectValue();
				//This only happens if response includes cache control headers. 
				//Jersey RestRequestCachingFilter is in charge of preparing this entry.
				if (entry.getObject() == null)
				{
					if (logger.isDebugEnabled())
						logger.debug("Insert data in cache");
					entry.setObject(data);
				}
				//In this case, server is not returning data, since object is cached and not has been modified
				else if ((notModified || entry.getStatus() == Status.NOT_MODIFIED.getStatusCode())
						&& entry.getObject() != null)
				{
					if (logger.isDebugEnabled())
						logger.debug("Retrieve data from cache");

					return entry.getObject();
				}

			}
			return data;

		}

		//Caching is not enabled

		//Paging methods
		if (webTarget != null)
			return method.invoke(restService, webTarget, builder);
		//Common retrieve and retrieveList methods
		else
		{
			if (type != null)
				return method.invoke(builder, type);
			else
				return method.invoke(builder);
		}
	}

	@Override
	@SuppressWarnings("unchecked")
	public <T> T manageRestCaching(final Builder builder, final Method method,
			final GenericType<T> type,
			final IRestPersistenceService<?> restService, final String key)
			throws Exception
	{

		T data = (T) manageRestCaching(builder, null, method, type, restService, key);
		return data;
	}

	/* (non-Javadoc)
	 * @see org.appverse.web.framework.backend.rest.managers.RestCachingManager#manageRestCaching(javax.ws.rs.client.Invocation.Builder, java.lang.reflect.Method, javax.ws.rs.core.Response, org.appverse.web.framework.backend.rest.services.integration.IRestPersistenceService, java.lang.String)
	 */
	@Override
	@SuppressWarnings("unchecked")
	public <T extends AbstractIntegrationBean> IntegrationPaginatedResult<T> manageRestCaching(
			final Builder builder,
			final WebTarget webTarget,
			final Method method,
			final IRestPersistenceService<T> restService, final String key) throws Exception {

		IntegrationPaginatedResult<T> data = (IntegrationPaginatedResult<T>) manageRestCaching(
				builder, webTarget, method, null, restService, key);
		return data;

	}

}