Support 'unless' expression for cache veto

Allow @Cachable, @CachePut and equivalent XML configuration to provide
a SpEL expression that can be used to veto putting an item into the
cache. Unlike 'condition' the 'unless' parameter is evaluated after
the method has been called and can therefore reference the #result.

For example:

    @Cacheable(value="book",
        condition="#name.length < 32",
        unless="#result.hardback")

This commit also allows #result to be referenced from @CacheEvict
expressions as long as 'beforeInvocation' is false.

Issue: SPR-8871

spring-context/src/test/resources/org/springframework/cache/config/cache-advice.xml

@@ -3,7 +3,7 @@
        xmlns:aop="http://www.springframework.org/schema/aop"
        xmlns:cache="http://www.springframework.org/schema/cache"
        xmlns:p="http://www.springframework.org/schema/p"
-       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd 
+       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
        		http://www.springframework.org/schema/cache http://www.springframework.org/schema/cache/spring-cache.xsd">
 
@@ -11,6 +11,7 @@
 		<cache:caching cache="default">
 			<cache:cacheable method="cache"/>
 			<cache:cacheable method="conditional" condition="#classField == 3"/>
+			<cache:cacheable method="unless" unless="#result > 10"/>
 			<cache:cacheable method="key" key="#p0"/>
 			<cache:cacheable method="nam*" key="#root.methodName"/>
 			<cache:cacheable method="rootVars" key="#root.methodName + #root.method.name + #root.targetClass + #root.target"/>
@@ -54,6 +55,7 @@
 			<cache:cacheable method="rootVars" key="#root.methodName + #root.method.name + #root.targetClass + #root.target"/>
 			<cache:cacheable method="cache"/>
 			<cache:cacheable method="conditional"/>
+			<cache:cacheable method="unless"/>
 			<cache:cacheable method="null*"/>
 		</cache:caching>
 		<cache:caching>
@@ -80,9 +82,9 @@
 			<cache:cache-evict method="multiConditionalCacheAndEvict" cache="secondary"/>
 			<cache:cache-put method="multiUpdate" cache="primary"/>
 			<cache:cache-put method="multiUpdate" cache="secondary"/>
-		</cache:caching>		
+		</cache:caching>
 	</cache:advice>
-		
+
 	<aop:config>
 		<aop:advisor advice-ref="cacheAdviceInterface" pointcut="execution(* *..DefaultCacheableService.*(..))" order="1"/>
 		<aop:advisor advice-ref="cacheAdviceClass" pointcut="execution(* *..AnnotatedClassCacheableService.*(..))" order="1"/>
@@ -98,12 +100,12 @@
 			</set>
 		</property>
 	</bean>
-	
+
 	<bean id="keyGenerator" class="org.springframework.cache.config.SomeKeyGenerator"/>
 
 	<bean id="debugInterceptor" class="org.springframework.aop.interceptor.DebugInterceptor"/>
-	
+
 	<bean id="service" class="org.springframework.cache.config.DefaultCacheableService"/>
-	
+
 	<bean id="classService" class="org.springframework.cache.config.AnnotatedClassCacheableService"/>
 </beans>