by:http://opensource.atlassian.com/confluence/spring/display/DISC/Caching+the+result+of+methods+using+Spring+and+EHCache
Introduction
Spring 1.1.1 introduced integration for EHCache
for general cache use.
I will show here a sample Interceptor that allows for declarative caching of methods results.
Configure EHCache using Spring IoC
Spring makes EHCache configuration very easy. All you need, is to provide a ehcache.xml file where you configure EHCache regions:
<ehcache>
????<!--?Sets?the?path?to?the?directory?where?cache?.data?files?are?created.
?????????If?the?path?is?a?Java?System?Property?it?is?replaced?by
?????????its?value?in?the?running?VM.
?????????The?following?properties?are?translated:
?????????user.home?-?User's?home?directory
?????????user.dir?-?User's?current?working?directory
?????????java.io.tmpdir?-?Default?temp?file?path?-->
????<diskStore?path="java.io.tmpdir"/>
????<!--Default?Cache?configuration.?These?will?applied?to?caches?programmatically?created?through
????????the?CacheManager.
????????The?following?attributes?are?required?for?defaultCache:
????????maxInMemory???????-?Sets?the?maximum?number?of?objects?that?will?be?created?in?memory
????????eternal???????????-?Sets?whether?elements?are?eternal.?If?eternal,??timeouts?are?ignored?and?the?element
????????????????????????????is?never?expired.
????????timeToIdleSeconds?-?Sets?the?time?to?idle?for?an?element?before?it?expires.
????????????????????????????i.e.?The?maximum?amount?of?time?between?accesses?before?an?element?expires
????????????????????????????Is?only?used?if?the?element?is?not?eternal.
????????????????????????????Optional?attribute.?A?value?of?0?means?that?an?Element?can?idle?for?infinity
????????timeToLiveSeconds?-?Sets?the?time?to?live?for?an?element?before?it?expires.
????????????????????????????i.e.?The?maximum?time?between?creation?time?and?when?an?element?expires.
????????????????????????????Is?only?used?if?the?element?is?not?eternal.
????????overflowToDisk????-?Sets?whether?elements?can?overflow?to?disk?when?the?in-memory?cache
????????????????????????????has?reached?the?maxInMemory?limit.
????????-->
????<cache?name="org.taha.cache.METHOD_CACHE"
????????maxElementsInMemory="300"
????????eternal="false"
????????timeToIdleSeconds="500"
????????timeToLiveSeconds="500"
????????overflowToDisk="true"
????????/>
</ehcache>
Our Interceptor will use region "org.taha.cache.METHOD_CACHE" to cache methods results.
Now we will use some Spring IoC to make this region accessible to our beans:
Bean methodCache creates cache region org.taha.cache.METHOD_CACHE.
Creating our MethodCacheInterceptor
The interceptor implements org.aopalliance.intercept.MethodInterceptor. Whenever it kicks-in, it first checks if the intercepted method is configured to be cached. This allows to selectively configure bean methods for caching. If the method call is configured for caching, the interceptor builds the cache key for the method and checks if the method result is in the cache. If so, the cached result is returned, otherwise the intercepted method is called and the result cached for further use.
/**//*
?*?Copyright?2002-2004?the?original?author?or?authors.
?*
?*?Licensed?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.taha.interceptor;
import?java.io.Serializable;
import?org.aopalliance.intercept.MethodInterceptor;
import?org.aopalliance.intercept.MethodInvocation;
import?org.apache.commons.logging.LogFactory;
import?org.apache.commons.logging.Log;
import?org.springframework.beans.factory.InitializingBean;
import?org.springframework.util.Assert;
import?net.sf.ehcache.Cache;
import?net.sf.ehcache.Element;
/**?*//**
?*?@author?<a?href="mailto:irbouh@gmail.com">Omar?Irbouh</a>
?*?@since?2004.10.07
?*/
public?class?MethodCacheInterceptor?implements?MethodInterceptor,?InitializingBean?
{
??privatestaticfinal?Log?logger?=?LogFactory.getLog(MethodCacheInterceptor.class);
??private?Cache?cache;
??/**?*//**
???*?sets?cache?name?to?be?used
???*/
??public?void?setCache(Cache?cache)?{
????this.cache?=?cache;
??}
??/**?*//**
???*?Checks?if?required?attributes?are?provided.
???*/
??public?void?afterPropertiesSet()?throws?Exception?{
????Assert.notNull(cache,?"A?cache?is?required.?Use?setCache(Cache)?to?provide?one.");
??}
??/**?*//**
???*?main?method
???*?caches?method?result?if?method?is?configured?for?caching
???*?method?results?must?be?serializable
???*/
??publicObject?invoke(MethodInvocation?invocation)?throws?Throwable?{
????String?targetName??=?invocation.getThis().getClass().getName();
????String?methodName??=?invocation.getMethod().getName();
????Object[]?arguments?=?invocation.getArguments();
????Object?result;
????logger.debug("looking?for?method?result?in?cache");
????String?cacheKey?=?getCacheKey(targetName,?methodName,?arguments);
????Element?element?=?cache.get(cacheKey);
????if?(element?==?null)?{
??????//call?target/sub-interceptor
??????logger.debug("calling?intercepted?method");
??????result?=?invocation.proceed();
??????//cache?method?result
??????logger.debug("caching?result");
??????element?=?new?Element(cacheKey,?(Serializable)?result);
??????cache.put(element);
????}
????return?element.getValue();
??}
??/**?*//**
???*?creates?cache?key:?targetName.methodName.argument0.argument1
???*/
??privateString?getCacheKey(String?targetName,
?????????????????????????????String?methodName,
?????????????????????????????Object[]?arguments)?{
????StringBuffer?sb?=?newStringBuffer();
????sb.append(targetName)
??????.append(".").append(methodName);
????if?((arguments?!=?null)?&&?(arguments.length?!=?0))?{
??????for?(int?i=0;?i<arguments.length;?i++)?{
????????sb.append(".")
??????????.append(arguments[i]);
??????}
????}
????return?sb.toString();
??}
}MethodCacheInterceptor source shows that:
- by default, all methods result are cached (methodNames is null)
- cache region is configured using IoC
- cacheKey takes in consideration method arguments
Using MethodCacheInterceptor
The following excerpt shows how to configure MethodCacheInterceptor:
It will be very helpfull to add the following to MethodCacheInterceptor:
- refactor the code so that the interceptor no longer depends on EHCache
- add arguments to methods configuration:
<property?name="methodNames">
??<list>
????<value>methodOne(java.lang.String,?int)</value>
????<value>methodOne(java.lang.String,?java.lang.String)</value>
??</list>
</property>
- add regular expressions to method configuration
<property?name="methodNames">
??<list>
????<value>add*</value>
??</list>
</property>
Changes:
- MethodCacheInterceptor now implements InitializingBean
- removed property methodNames and setter setMethodNames(java.lang.String)
- MethodCacheInterceptor can be configured using regular PointCutAdvisor
- using org.springframework.util.Assert to eagerly check if property cache is not null