Java tutorial
package net.nelz.simplesm.aop; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Pointcut; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.ProceedingJoinPoint; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import net.nelz.simplesm.api.ReadThroughAssignCache; import java.lang.reflect.Method; /** Copyright (c) 2008, 2009 Nelson Carpentier Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ @Aspect public class ReadThroughAssignCacheAdvice extends CacheBase { private static final Log LOG = LogFactory.getLog(ReadThroughAssignCacheAdvice.class); @Pointcut("@annotation(net.nelz.simplesm.api.ReadThroughAssignCache)") public void getSingleAssign() { } @Around("getSingleAssign()") public Object cacheSingleAssign(final ProceedingJoinPoint pjp) throws Throwable { // This is injected caching. If anything goes wrong in the caching, LOG the crap outta it, // but do not let it surface up past the AOP injection itself. final String cacheKey; final AnnotationData annotationData; try { final Method methodToCache = getMethodToCache(pjp); final ReadThroughAssignCache annotation = methodToCache.getAnnotation(ReadThroughAssignCache.class); annotationData = AnnotationDataBuilder.buildAnnotationData(annotation, ReadThroughAssignCache.class, methodToCache); cacheKey = buildCacheKey(annotationData.getAssignedKey(), annotationData); final Object result = cache.get(cacheKey); if (result != null) { LOG.debug("Cache hit."); return (result instanceof PertinentNegativeNull) ? null : result; } } catch (Throwable ex) { LOG.warn("Caching on " + pjp.toShortString() + " aborted due to an error.", ex); return pjp.proceed(); } final Object result = pjp.proceed(); // This is injected caching. If anything goes wrong in the caching, LOG the crap outta it, // but do not let it surface up past the AOP injection itself. try { final Object submission = (result == null) ? new PertinentNegativeNull() : result; cache.set(cacheKey, annotationData.getExpiration(), submission); } catch (Throwable ex) { LOG.warn("Caching on " + pjp.toShortString() + " aborted due to an error.", ex); } return result; } }