Add OSGi condition which is satisfied once the default Ehcache services

docs/src/docs/asciidoc/user/osgi.adoc

@@ -53,6 +53,8 @@ Additional features can then be added by including one or more of:
 * `org.ehcache:ehcache-clustered`
 * `org.ehcache:ehcache-transactions`
 
+In order to defer starting OSGi DS components which leverage `org.ehcache.core.CacheManager` (for example via `CacheManagerBuilder`) or `javax.cache.spi.CachingProvider` (for example via `javax.cache.Caching`) until all relevant services for Ehcache are available one can leverage the https://docs.osgi.org/specification/osgi.core/8.0.0/service.condition.html[OSGi condition] with id `ehcache`.
+
 === Reverting to JDK Service Lookup
 
 If the `org.ehcache.core.osgi` property is set to `"false"` as either a framework or system property then Ehcache will

ehcache-impl/build.gradle

@@ -54,6 +54,8 @@ dependencies {
   implementation group: 'org.ehcache', name: 'sizeof', version: parent.sizeofVersion
   implementation group: 'org.terracotta', name: 'terracotta-utilities-tools', version: parent.terracottaUtilitiesVersion
   compileOnly 'org.osgi:org.osgi.service.component.annotations:1.3.0'
+  compileOnly 'org.osgi:org.osgi.service.component:1.3.0'
+  implementation 'org.osgi:org.osgi.service.condition:1.0.0'
   testImplementation project(':core-spi-test')
   testImplementation 'org.ow2.asm:asm:6.2'
   testImplementation 'org.ow2.asm:asm-commons:6.2'
@@ -65,7 +67,7 @@ jar {
   bnd (
     'Export-Package': '!org.ehcache.impl.internal.*, org.ehcache.impl.*, org.ehcache.config.builders, ' +
       'org.ehcache.impl.internal.spi.loaderwriter', //ugly 107 induced internal export wart
-    'Import-Package': '!sun.misc, !javax.annotation, *',
+    'Import-Package': '!sun.misc, !javax.annotation, org.osgi.service.condition;resolution:=optional, *',
   )
 }
 

ehcache-impl/src/main/java/org/ehcache/impl/osgi/EhcacheReadyCondition.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright Terracotta, Inc.
+ *
+ * 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.ehcache.impl.osgi;
+
+import org.ehcache.core.EhcacheManager;
+import org.ehcache.core.events.CacheEventDispatcherFactory;
+import org.ehcache.core.events.CacheEventListenerProvider;
+import org.ehcache.core.spi.service.ServiceFactory;
+import org.ehcache.core.spi.store.Store;
+import org.ehcache.impl.internal.spi.resilience.DefaultResilienceStrategyProvider;
+import org.ehcache.impl.internal.store.tiering.TieredStore;
+import org.ehcache.impl.internal.store.tiering.TieredStoreProviderFactory;
+import org.ehcache.spi.loaderwriter.CacheLoaderWriterProvider;
+import org.ehcache.spi.loaderwriter.WriteBehindProvider;
+import org.ehcache.spi.resilience.ResilienceStrategyProvider;
+import org.ehcache.spi.serialization.SerializationProvider;
+import org.osgi.service.component.ComponentConstants;
+import org.osgi.service.component.annotations.Component;
+import org.osgi.service.component.annotations.Reference;
+import org.osgi.service.condition.Condition;
+
+/**
+ * The condition is satisfied once all default {@link ServiceFactory} classes mentioned in {@link EhcacheManager} or {@link EhcacheCachingProvider} are registered.
+ * Those are
+ * <ol>
+ * <li>{@link Store.Provider} provided through DS component {@link TieredStoreProviderFactory}</li>
+ * <li>{@link CacheLoaderWriterProvider} provided through DS component {@link DefaultCacheLoaderWriterProviderFactory}</li>
+ * <li>{@link WriteBehindProvider} provided through DS component {@link WriteBehindProviderFactory}</li>
+ * <li>{@link CacheEventDispatcherFactory} provided through DS component {@link CacheEventNotificationListenerServiceProviderFactory}</li>
+ * <li>{@link CacheEventListenerProvider} provided through DS component {@link DefaultCacheEventListenerProviderFactory}</li>
+ * <li>{@link ResilienceStrategyProvider} provided through DS component {@link DefaultResilienceStrategyProvider}</li>
+ * <li>{@link SerializationProvider} provided through DS component {@link DefaultSerializationProviderFactory}</li>
+ * </ol>
+ * Because those services are not provided directly but through {@link ServiceFactory} this condition references directly the responsible default factories (via their component name)
+ */
+@Component(property = Condition.CONDITION_ID + "=ehcache")
+public class EhcacheReadyCondition implements Condition {
+
+    @Reference(target = "("+ComponentConstants.COMPONENT_NAME+"=org.ehcache.impl.internal.store.tiering.TieredStoreProviderFactory)")
+    private ServiceFactory<TieredStore.Provider> storeProviderFactory;
+
+    @Reference(target = "("+ComponentConstants.COMPONENT_NAME+"=org.ehcache.impl.internal.spi.loaderwriter.DefaultCacheLoaderWriterProviderFactory)")
+    private ServiceFactory<CacheLoaderWriterProvider> cacheLoaderWriterProviderFactory;
+
+    @Reference(target = "("+ComponentConstants.COMPONENT_NAME+"=org.ehcache.impl.internal.loaderwriter.writebehind.WriteBehindProviderFactory)")
+    private ServiceFactory<WriteBehindProvider> writeBehindProviderFactory;
+
+    @Reference(target = "("+ComponentConstants.COMPONENT_NAME+"=org.ehcache.impl.internal.events.CacheEventNotificationListenerServiceProviderFactory)")
+    private ServiceFactory<CacheEventDispatcherFactory> cacheEventNotificationListenerServiceProviderFactory;
+
+    @Reference(target = "("+ComponentConstants.COMPONENT_NAME+"=org.ehcache.impl.internal.spi.event.DefaultCacheEventListenerProviderFactory)")
+    private ServiceFactory<CacheEventListenerProvider> cacheEventListenerProviderFactory;
+
+    @Reference(target = "("+ComponentConstants.COMPONENT_NAME+"=org.ehcache.impl.internal.spi.resilience.DefaultResilienceStrategyProviderFactory)")
+    private ServiceFactory<ResilienceStrategyProvider> resilienceStrategyProviderFactory;
+
+    @Reference(target = "("+ComponentConstants.COMPONENT_NAME+"=org.ehcache.impl.internal.spi.serialization.DefaultSerializationProviderFactory)")
+    private ServiceFactory<SerializationProvider> serializationProviderFactory;
+}