Add a concrete o.s.g.cache.RepositoryCacheLoader class, which implements org.apache.geode.cache.CacheLoader and uses (delegates to) a Spring Data CrudRepository.

spring-geode/src/main/java/org/springframework/geode/cache/RepositoryCacheLoader.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2019 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.geode.cache;
+
+import java.util.function.Supplier;
+
+import org.apache.geode.cache.CacheLoader;
+import org.apache.geode.cache.CacheLoaderException;
+import org.apache.geode.cache.CacheRuntimeException;
+import org.apache.geode.cache.LoaderHelper;
+import org.springframework.data.repository.CrudRepository;
+import org.springframework.geode.cache.support.RepositoryCacheLoaderWriterSupport;
+
+/**
+ * A {@link CacheLoader} implementation backed by a Spring Data {@link CrudRepository} used to load an entity
+ * from an external data source.
+ *
+ * @author John Blum
+ * @see org.apache.geode.cache.CacheLoader
+ * @see org.springframework.data.repository.CrudRepository
+ * @see org.springframework.geode.cache.support.CacheLoaderSupport
+ * @since 1.1.0
+ */
+@SuppressWarnings("unused")
+public class RepositoryCacheLoader<T, ID> extends RepositoryCacheLoaderWriterSupport<T, ID> {
+
+  protected static final String CACHE_LOAD_EXCEPTION_MESSAGE = "Error while loading Entity [%s] with Repository [%s]";
+
+  public RepositoryCacheLoader(CrudRepository<T, ID> repository) {
+    super(repository);
+  }
+
+  @Override
+  public T load(LoaderHelper<ID, T> helper) throws CacheLoaderException {
+
+    try {
+      return getRepository().findById(helper.getKey()).orElse(null);
+    }
+    catch (Exception cause) {
+      throw newCacheRuntimeException(() -> String.format(CACHE_LOAD_EXCEPTION_MESSAGE,
+          helper.getKey(), getRepository().getClass().getName()), cause);
+    }
+  }
+
+  @Override
+  protected CacheRuntimeException newCacheRuntimeException(Supplier<String> messageSupplier, Throwable cause) {
+    return new CacheLoaderException(messageSupplier.get(), cause);
+  }
+}

spring-geode/src/test/java/org/springframework/geode/cache/RepositoryCacheLoaderUnitTests.java

@@ -0,0 +1,140 @@
+/*
+ * Copyright 2019 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.geode.cache;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyZeroInteractions;
+import static org.mockito.Mockito.when;
+
+import java.util.Optional;
+
+import org.apache.geode.cache.CacheLoaderException;
+import org.apache.geode.cache.CacheRuntimeException;
+import org.apache.geode.cache.LoaderHelper;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+import org.springframework.core.env.Environment;
+import org.springframework.dao.IncorrectResultSizeDataAccessException;
+import org.springframework.data.repository.CrudRepository;
+
+/**
+ * Unit Test for {@link RepositoryCacheLoader}.
+ *
+ * @author John Blum
+ * @see org.junit.Test
+ * @see org.mockito.Mockito
+ * @see org.springframework.geode.cache.RepositoryCacheLoader
+ * @since 1.1.0
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class RepositoryCacheLoaderUnitTests {
+
+	@Mock
+	private CrudRepository<Object, Object> mockCrudRepository;
+
+	@Mock
+	private Environment mockEnvironment;
+
+	@Mock
+	private LoaderHelper<Object, Object> mockLoaderHelper;
+
+	private Object testEntity = new Object();
+
+	private RepositoryCacheLoader<Object, Object> cacheLoader;
+
+	@Before
+	public void setup() {
+
+		this.cacheLoader = new RepositoryCacheLoader<>(this.mockCrudRepository)
+			.with(this.mockEnvironment);
+	}
+
+	@After
+	public void tearDown() {
+		verifyZeroInteractions(this.mockEnvironment);
+	}
+
+	@Test
+	public void loadsEntitySuccessfully() {
+
+		when(this.mockCrudRepository.findById(eq("TestKey"))).thenReturn(Optional.of(this.testEntity));
+		when(this.mockLoaderHelper.getKey()).thenReturn("TestKey");
+
+		assertThat(this.cacheLoader.load(this.mockLoaderHelper)).isEqualTo(this.testEntity);
+
+		verify(this.mockLoaderHelper, times(1)).getKey();
+		verify(this.mockCrudRepository, times(1)).findById(eq("TestKey"));
+	}
+
+	@Test
+	public void loadReturnsNull() {
+
+		when(this.mockCrudRepository.findById(eq("TestKey"))).thenReturn(Optional.empty());
+		when(this.mockLoaderHelper.getKey()).thenReturn("TestKey");
+
+		assertThat(this.cacheLoader.load(this.mockLoaderHelper)).isNull();
+
+		verify(this.mockLoaderHelper, times(1)).getKey();
+		verify(this.mockCrudRepository, times(1)).findById(eq("TestKey"));
+	}
+
+	@Test(expected = CacheLoaderException.class)
+	public void loadThrowsException() {
+
+		when(this.mockCrudRepository.findById(eq("TestKey")))
+			.thenThrow(new IncorrectResultSizeDataAccessException(1, 0));
+
+		when(this.mockLoaderHelper.getKey()).thenReturn("TestKey");
+
+		try {
+			this.cacheLoader.load(this.mockLoaderHelper);
+		}
+		catch (CacheLoaderException expected) {
+
+			assertThat(expected).hasMessage(RepositoryCacheLoader.CACHE_LOAD_EXCEPTION_MESSAGE,
+				"TestKey", this.mockCrudRepository.getClass().getName());
+
+			assertThat(expected).hasCauseInstanceOf(IncorrectResultSizeDataAccessException.class);
+			assertThat(expected.getCause()).hasNoCause();
+
+			throw expected;
+		}
+		finally {
+			verify(this.mockLoaderHelper, times(2)).getKey();
+			verify(this.mockCrudRepository, times(1)).findById(eq("TestKey"));
+		}
+	}
+
+	@Test
+	@SuppressWarnings("all")
+	public void newCacheRuntimeExceptionIsCorrect() {
+
+		RuntimeException cause = new RuntimeException("TEST");
+
+		CacheRuntimeException cacheRuntimeException = this.cacheLoader.newCacheRuntimeException(() -> "TEST", cause);
+
+		assertThat(cacheRuntimeException).isInstanceOf(CacheLoaderException.class);
+		assertThat(cacheRuntimeException.getMessage()).isEqualTo("TEST");
+		assertThat(cacheRuntimeException.getCause()).isEqualTo(cause);
+	}
+}