DATAGEODE-244 - Add RegionResolver interface to enable strategic or lazy Region resolution when & where needed.

spring-data-geode/src/main/java/org/springframework/data/gemfire/RegionResolver.java

@@ -0,0 +1,69 @@
+/*
+ * 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 org.apache.geode.cache.Region;
+
+import org.springframework.lang.NonNull;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * The {@link RegionResolver} interface is a {@literal Strategy} interface used to encapsulate different algorithms
+ * (Strategies) used to resolve a cache {@link Region}.
+ *
+ * @author John Blum
+ * @see org.apache.geode.cache.Region
+ * @since 2.3.0
+ */
+@FunctionalInterface
+public interface RegionResolver {
+
+	/**
+	 * Returns a {@link Region} resolved with the given {@link String name}.
+	 *
+	 * @param <K> {@link Class type} of the {@link Region} key.
+	 * @param <V> {@link Class type} of the {@link Region} value;
+	 * @param regionName {@link String name} of the {@link Region} to resolve; may be {@literal null}.
+	 * @return the resolved {@link Region} with the given {@link String name}; may be {@literal null}.
+	 * @see org.apache.geode.cache.Region
+	 * @see java.lang.String
+	 */
+	@Nullable <K, V> Region<K, V> resolve(@Nullable String regionName);
+
+	/**
+	 * Requires a {@link Region} resolved from the given {@link String name}.
+	 *
+	 * @param <K> {@link Class type} of the {@link Region} key.
+	 * @param <V> {@link Class type} of the {@link Region} value;
+	 * @param regionName {@link String name} of the {@link Region} to resolve; must not be {@literal null}.
+	 * @return the resolved {@link Region} with the given {@link String name}; never {@literal null}.
+	 * @throws IllegalStateException if the resolved {@link Region} is {@literal null}, i.e. does not exist.
+	 * @see org.apache.geode.cache.Region
+	 * @see java.lang.String
+	 * @see #resolve(String)
+	 */
+	default @NonNull <K, V> Region<K, V> require(@NonNull String regionName) {
+
+		Region<K, V> region = StringUtils.hasText(regionName) ? resolve(regionName) : null;
+
+		Assert.state(region != null,
+			() -> String.format("Region with name [%s] not found", regionName));
+
+		return region;
+	}
+}

spring-data-geode/src/test/java/org/springframework/data/gemfire/RegionResolverUnitTests.java

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+/*
+ * 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.ArgumentMatchers.anyString;
+import static org.mockito.ArgumentMatchers.eq;
+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.Region;
+
+/**
+ * Unit Tests for {@link RegionResolver}.
+ *
+ * @author John Blum
+ * @see org.junit.Test
+ * @see org.mockito.Mockito
+ * @see org.apache.geode.cache.Region
+ * @see org.springframework.data.gemfire.RegionResolver
+ * @since 2.3.0
+ */
+public class RegionResolverUnitTests {
+
+	@Test
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	public void requiresRegionForNameReturnsRegion() {
+
+		Region mockRegion = mock(Region.class);
+
+		RegionResolver regionResolver = mock(RegionResolver.class);
+
+		when(regionResolver.require(anyString())).thenCallRealMethod();
+		when(regionResolver.resolve(eq("MockRegion"))).thenReturn(mockRegion);
+
+		assertThat(regionResolver.require("MockRegion")).isEqualTo(mockRegion);
+
+		verify(regionResolver, times(1)).resolve(eq("MockRegion"));
+		verifyNoInteractions(mockRegion);
+	}
+
+	@Test(expected = IllegalStateException.class)
+	public void requiredRegionResolvingToNullThrowsIllegalStateException() {
+
+		RegionResolver regionResolver = mock(RegionResolver.class);
+
+		when(regionResolver.require(anyString())).thenCallRealMethod();
+		when(regionResolver.resolve(anyString())).thenReturn(null);
+
+		try {
+			regionResolver.require("TestRegion");
+		}
+		catch (IllegalStateException expected) {
+
+			assertThat(expected).hasMessage("Region with name [TestRegion] not found");
+			assertThat(expected).hasNoCause();
+
+			throw expected;
+		}
+		finally {
+			verify(regionResolver, times(1)).resolve(eq("TestRegion"));
+		}
+	}
+}