Favor JSR-107 provider if present

Previously, native cache libraries were favored over a standard JSR-107
implementation. If a user has a working setup using JCache with one
provider and switch to another provider, his setup may be broken if we
happen to provide a native support for the new provider.

We now consistently favor JSR-107 if it is present. Native support can
still be enabled via the `spring.cache.type` property.

Closes gh-3822

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/cache/CacheType.java

@@ -31,6 +31,11 @@ public enum CacheType {
 	 */
 	GENERIC,
 
+	/**
+	 * JCache (JSR-107) backed caching.
+	 */
+	JCACHE,
+
 	/**
 	 * EhCache backed caching.
 	 */
@@ -46,11 +51,6 @@ public enum CacheType {
 	 */
 	INFINISPAN,
 
-	/**
-	 * JCache (JSR-107) backed caching.
-	 */
-	JCACHE,
-
 	/**
 	 * Redis backed caching.
 	 */

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -2806,10 +2806,10 @@ implementations are only provided by the `spring-context-support` jar.
 Spring Boot tries to detect the following providers (in this order):
 
 * <<boot-features-caching-provider-generic,Generic>>
+* <<boot-features-caching-provider-jcache,JCache (JSR-107)>>
 * <<boot-features-caching-provider-ehcache2,EhCache 2.x>>
 * <<boot-features-caching-provider-hazelcast,Hazelcast>>
 * <<boot-features-caching-provider-infinispan,Infinispan>>
-* <<boot-features-caching-provider-jcache,JCache (JSR-107)>>
 * <<boot-features-caching-provider-redis,Redis>>
 * <<boot-features-caching-provider-guava,Guava>>
 * <<boot-features-caching-provider-simple,Simple>>
@@ -2826,6 +2826,38 @@ Generic caching is used if the context defines _at least_ one
 
 
 
+[[boot-features-caching-provider-jcache]]
+==== JCache
+JCache is bootstrapped via the presence of a `javax.cache.spi.CachingProvider` on the
+classpath (i.e. a JSR-107 compliant caching library). It might happen than more that one
+provider is present, in which case the provider must be explicitly specified. Even if the
+JSR-107 standard does not enforce a standardized way to define the location of the
+configuration file, Spring Boot does its best to accommodate with implementation details.
+
+[source,properties,indent=0]
+----
+    # Only necessary if more than one provider is present
+	spring.cache.jcache.provider=com.acme.MyCachingProvider
+	spring.cache.jcache.config=classpath:acme.xml
+----
+
+NOTE: Since a cache library may offer both a native implementation and JSR-107 support
+Spring Boot will prefer the JSR-107 support so that the same features are available if
+you switch to a different JSR-107 implementation.
+
+There are several ways to customize the underlying `javax.cache.cacheManager`:
+
+* Caches can be created on startup via the `spring.cache.cache-names` property. If a custom
+`javax.cache.configuration.Configuration` bean is defined, it is used to customize them.
+* `org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizer` beans are
+invoked with the reference of the `CacheManager` for full customization.
+
+TIP: If a standard `javax.cache.CacheManager` bean is defined, it is wrapped
+automatically in a `org.springframework.cache.CacheManager` implementation that the
+abstraction expects. No further customization is applied on it.
+
+
+
 [[boot-features-caching-provider-ehcache2]]
 ==== EhCache 2.x
 EhCache 2.x is used if a file named `ehcache.xml` can be found at the root of the
@@ -2868,38 +2900,6 @@ Caches can be created on startup via the `spring.cache.cache-names` property. If
 
 
 
-[[boot-features-caching-provider-jcache]]
-==== JCache
-JCache is bootstrapped via the presence of a `javax.cache.spi.CachingProvider` on the
-classpath (i.e. a JSR-107 compliant caching library). It might happen than more that one
-provider is present, in which case the provider must be explicitly specified. Even if the
-JSR-107 standard does not enforce a standardized way to define the location of the
-configuration file, Spring Boot does its best to accommodate with implementation details.
-
-[source,properties,indent=0]
-----
-    # Only necessary if more than one provider is present
-	spring.cache.jcache.provider=com.acme.MyCachingProvider
-	spring.cache.jcache.config=classpath:acme.xml
-----
-
-NOTE: Since a cache library may offer both a native implementation and JSR-107 support
-it is advised to set the `spring.cache.type` to `jcache` to force that mode if that's
-what you want.
-
-There are several ways to customize the underlying `javax.cache.cacheManager`:
-
-* Caches can be created on startup via the `spring.cache.cache-names` property. If a custom
-`javax.cache.configuration.Configuration` bean is defined, it is used to customize them.
-* `org.springframework.boot.autoconfigure.cache.JCacheManagerCustomizer` beans are
-invoked with the reference of the `CacheManager` for full customization.
-
-TIP: If a standard `javax.cache.CacheManager` bean is defined, it is wrapped
-automatically in a `org.springframework.cache.CacheManager` implementation that the
-abstraction expects. No further customization is applied on it.
-
-
-
 [[boot-features-caching-provider-redis]]
 ==== Redis
 If Redis is available and configured, the `RedisCacheManager` is auto-configured. It is

spring-boot-samples/spring-boot-sample-cache/README.adoc

@@ -10,6 +10,7 @@ abstraction is supported by many caching libraries, including:
 * `Redis`
 * `Guava`
 * Simple provider based on `ConcurrentHashMap`
+* Generic provider based on `org.springframework.Cache` bean definition(s)
 
 The sample defines a simple `CountryService` that caches countries by ISO code. When
 the application starts a client invokes the service with a random code every 500ms. You
@@ -35,6 +36,25 @@ as explained below.
 
 
 
+=== JCache (JSR-107)
+If you want to configure your cache infrastructure via the standard, you need a compliant
+implementation and the JSR-107 api. You first need to add `javax.cache:cache-api` to your
+project. Then you could try the following:
+
+* `Hazelcast`: add `com.hazelcast:hazelcast`
+* `Infinispan`: add `org.infinispan:infinispan-jcache`
+
+TIP: Certain cache providers do not create a default cache on-the-fly if it does not exist
+so you might need to update the sample to create the caches on startup or specify the
+location to the provider-specific file via the `spring.cache.jcache.config` property.
+
+NOTE: Any other JSR-107 compliant provider is also supported but Spring Boot may not
+offer a dependency management entry for it. You will have to add it with the version
+of the library that you want to use.
+
+
+
+
 === EhCache 2.x
 Simply add the `net.sf.ehcache:ehcache` dependency to the project. Since there is a
 default `ehcache.xml` configuration file at the root of the classpath, it is automatically
@@ -59,20 +79,6 @@ can set the `spring.cache.infinispan.config` property to use the provided
 
 
 
-=== JCache (JSR-107)
-If you want to configure your cache infrastructure via the standard, you need a compliant
-implementation. You could try the following:
-
-* `Hazelcast`: add `com.hazelcast:hazelcast`
-* `Infinispan`: add `org.infinispan:infinispan-jcache`
-
-
-Since Spring Boot supports the native cache library and the JCache wrapper, you
-should set the `spring.cache.type` property to `jcache` to specify that you want the
-cache manager to be auto-configured that way.
-
-
-
 === Redis
 Add the `spring-boot-starter-redis` and make sure it is configured properly (by default,
 a redis instance with the default settings is expected on your local box).

spring-boot-samples/spring-boot-sample-cache/pom.xml

@@ -33,6 +33,15 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-actuator</artifactId>
 		</dependency>
+
+		<!-- JSR-107 API (uncomment to try the JCache support) -->
+		<!--
+		<dependency>
+			<groupId>javax.cache</groupId>
+			<artifactId>cache-api</artifactId>
+		</dependency>
+		-->
+		
 		<!-- Additional cache providers (uncomment to try them) -->
 		<!--
 		<dependency>

spring-boot-samples/spring-boot-sample-cache/src/main/resources/application.properties

@@ -7,7 +7,6 @@
 #
 # JCache configuration (example with hazelcast).
 #
-#spring.cache.type=jcache
 #spring.cache.jcache.config=hazelcast.xml