From 7caaa4fe75ad5481cf4f3594417fae6e8a444ac3 Mon Sep 17 00:00:00 2001
From: John Blum <jblum@pivotal.io>
Date: Fri, 27 Mar 2020 17:50:06 -0700
Subject: [PATCH] DATAGEODE-318 - Introduce a CacheResolver Strategy interface
 for resolving GemFireCache instances.

---
 .../data/gemfire/CacheResolver.java           | 54 ++++++++++++++++++
 .../data/gemfire/CacheResolverUnitTests.java  | 57 +++++++++++++++++++
 2 files changed, 111 insertions(+)
 create mode 100644 spring-data-geode/src/main/java/org/springframework/data/gemfire/CacheResolver.java
 create mode 100644 spring-data-geode/src/test/java/org/springframework/data/gemfire/CacheResolverUnitTests.java

diff --git a/spring-data-geode/src/main/java/org/springframework/data/gemfire/CacheResolver.java b/spring-data-geode/src/main/java/org/springframework/data/gemfire/CacheResolver.java
new file mode 100644
index 00000000..5a2d25ea
--- /dev/null
+++ b/spring-data-geode/src/main/java/org/springframework/data/gemfire/CacheResolver.java
@@ -0,0 +1,54 @@
+/*
+ * Copyright 2020 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
+ *
+ *      https://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.springframework.data.gemfire;
+
+import java.util.function.Supplier;
+
+import org.apache.geode.cache.GemFireCache;
+
+/**
+ * Strategy interface for resolving a instance reference to a {@link GemFireCache}.
+ *
+ * @author John Blum
+ * @param <T> {@link Class subclass} of {@link GemFireCache}.
+ * @see java.util.function.Supplier
+ * @see org.apache.geode.cache.Cache
+ * @see org.apache.geode.cache.GemFireCache
+ * @see org.apache.geode.cache.client.ClientCache
+ * @since 2.3.0
+ */
+@FunctionalInterface
+public interface CacheResolver<T extends GemFireCache> extends Supplier<T> {
+
+	/**
+	 * Gets the resolved instance of the {@link GemFireCache}.
+	 *
+	 * @return the resolved instance of the {@link GemFireCache}.
+	 * @see #resolve()
+	 */
+	@Override
+	default T get() {
+		return resolve();
+	}
+
+	/**
+	 * Resolves the instance reference to the {@link GemFireCache} implementation.
+	 *
+	 * @return a instance reference to a {@link GemFireCache} implementation.
+	 */
+	T resolve();
+
+}
diff --git a/spring-data-geode/src/test/java/org/springframework/data/gemfire/CacheResolverUnitTests.java b/spring-data-geode/src/test/java/org/springframework/data/gemfire/CacheResolverUnitTests.java
new file mode 100644
index 00000000..ea8db430
--- /dev/null
+++ b/spring-data-geode/src/test/java/org/springframework/data/gemfire/CacheResolverUnitTests.java
@@ -0,0 +1,57 @@
+/*
+ * Copyright 2020 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
+ *
+ *      https://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.springframework.data.gemfire;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+import static org.mockito.Mockito.when;
+
+import org.junit.Test;
+
+import org.apache.geode.cache.GemFireCache;
+
+/**
+ * Unit Tests for {@link CacheResolver}.
+ *
+ * @author John Blum
+ * @see org.junit.Test
+ * @see org.mockito.Mockito
+ * @see org.apache.geode.cache.GemFireCache
+ * @see org.springframework.data.gemfire.CacheResolver
+ * @since 2.3.0
+ */
+public class CacheResolverUnitTests {
+
+	@Test
+	@SuppressWarnings("rawtypes")
+	public void getCallsResolve() {
+
+		GemFireCache mockCache = mock(GemFireCache.class);
+
+		CacheResolver mockCacheResolver = mock(CacheResolver.class);
+
+		when(mockCacheResolver.get()).thenCallRealMethod();
+		when(mockCacheResolver.resolve()).thenReturn(mockCache);
+
+		assertThat(mockCacheResolver.get()).isEqualTo(mockCache);
+
+		verify(mockCacheResolver, times(1)).resolve();
+		verifyNoInteractions(mockCache);
+	}
+}