[[cache-declarative-xml]]
= Declarative XML-based Caching

If annotations are not an option (perhaps due to having no access to the sources
or no external code), you can use XML for declarative caching. So, instead of
annotating the methods for caching, you can specify the target method and the
caching directives externally (similar to the declarative transaction management
xref:data-access/transaction/declarative/first-example.adoc[advice]). The example
from the previous section can be translated into the following example:

[source,xml,indent=0]
[subs="verbatim"]
----
	<!-- the service we want to make cacheable -->
	<bean id="bookService" class="x.y.service.DefaultBookService"/>

	<!-- cache definitions -->
	<cache:advice id="cacheAdvice" cache-manager="cacheManager">
		<cache:caching cache="books">
			<cache:cacheable method="findBook" key="#isbn"/>
			<cache:cache-evict method="loadBooks" all-entries="true"/>
		</cache:caching>
	</cache:advice>

	<!-- apply the cacheable behavior to all BookService interfaces -->
	<aop:config>
		<aop:advisor advice-ref="cacheAdvice" pointcut="execution(* x.y.BookService.*(..))"/>
	</aop:config>

	<!-- cache manager definition omitted -->
----

In the preceding configuration, the `bookService` is made cacheable. The caching semantics
to apply are encapsulated in the `cache:advice` definition, which causes the `findBooks`
method to be used for putting data into the cache and the `loadBooks` method for evicting
data. Both definitions work against the `books` cache.

The `aop:config` definition applies the cache advice to the appropriate points in the
program by using the AspectJ pointcut expression (more information is available in
xref:core/aop.adoc[Aspect Oriented Programming with Spring]). In the preceding example,
all methods from the `BookService` are considered and the cache advice is applied to them.

The declarative XML caching supports all of the annotation-based model, so moving between
the two should be fairly easy. Furthermore, both can be used inside the same application.
The XML-based approach does not touch the target code. However, it is inherently more
verbose. When dealing with classes that have overloaded methods that are targeted for
caching, identifying the proper methods does take an extra effort, since the `method`
argument is not a good discriminator. In these cases, you can use the AspectJ pointcut
to cherry pick the target methods and apply the appropriate caching functionality.
However, through XML, it is easier to apply package or group or interface-wide caching
(again, due to the AspectJ pointcut) and to create template-like definitions (as we did
in the preceding example by defining the target cache through the `cache:definitions`
`cache` attribute).
