DATAREST-511 - Support for executing repository methods returning Optionals.

Added an UnwrappingRepositoryInvokerFactory that transparently unwraps JDK 8 and Guava Optionals to make sure the consuming code works with values or plain nulls correctly.

spring-data-rest-core/pom.xml

@@ -65,6 +65,13 @@
 			<version>${jackson}</version>
 		</dependency>
 
+		<dependency>
+			<groupId>com.google.guava</groupId>
+			<artifactId>guava</artifactId>
+			<version>${guava}</version>
+			<optional>true</optional>
+		</dependency>
+
 	</dependencies>
 
 </project>

spring-data-rest-core/src/main/java/org/springframework/data/rest/core/support/UnwrappingRepositoryInvokerFactory.java

@@ -0,0 +1,243 @@
+/*
+ * Copyright 2015 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
+ *
+ *      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.springframework.data.rest.core.support;
+
+import java.io.Serializable;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Sort;
+import org.springframework.data.repository.support.RepositoryInvoker;
+import org.springframework.data.repository.support.RepositoryInvokerFactory;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.MultiValueMap;
+
+/**
+ * {@link RepositoryInvokerFactory} that wraps the {@link RepositoryInvokerFactory} returned by the delegate with one
+ * that automatically unwraps JDK 8 {@link Optional} and Guava {@link com.google.common.base.Optional}s.
+ * 
+ * @author Oliver Gierke
+ */
+public class UnwrappingRepositoryInvokerFactory implements RepositoryInvokerFactory {
+
+	private static final List<Converter<Object, Object>> CONVERTERS;
+
+	static {
+
+		List<Converter<Object, Object>> converters = new ArrayList<Converter<Object, Object>>();
+		ClassLoader classLoader = UnwrappingRepositoryInvokerFactory.class.getClassLoader();
+
+		// Add unwrapper for Java 8 Optional
+
+		if (ClassUtils.isPresent("java.util.Optional", classLoader)) {
+			converters.add(new Converter<Object, Object>() {
+				@Override
+				public Object convert(Object source) {
+					return source instanceof Optional ? ((Optional<?>) source).orElse(null) : source;
+				}
+			});
+		}
+
+		// Add unwrapper for Guava Optional
+
+		if (ClassUtils.isPresent("com.google.common.base.Optional", classLoader)) {
+
+			converters.add(new Converter<Object, Object>() {
+				@Override
+				public Object convert(Object source) {
+					return source instanceof com.google.common.base.Optional ? ((com.google.common.base.Optional<?>) source)
+							.orNull() : source;
+				}
+			});
+		}
+
+		CONVERTERS = Collections.unmodifiableList(converters);
+	}
+
+	private final RepositoryInvokerFactory delegate;
+
+	/**
+	 * Creates a new {@link UnwrappingRepositoryInvokerFactory}.
+	 * 
+	 * @param delegate must not be {@literal null}.
+	 */
+	public UnwrappingRepositoryInvokerFactory(RepositoryInvokerFactory delegate) {
+
+		Assert.notNull(delegate, "Delegate RepositoryInvokerFactory must not be null!");
+
+		this.delegate = delegate;
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.repository.support.RepositoryInvokerFactory#getInvokerFor(java.lang.Class)
+	 */
+	@Override
+	public RepositoryInvoker getInvokerFor(Class<?> domainType) {
+		return new UnwrappingRepositoryInvoker(delegate.getInvokerFor(domainType), CONVERTERS);
+	}
+
+	/**
+	 * {@link RepositoryInvoker} that post-processes invocations of {@link RepositoryInvoker#invokeFindOne(Serializable)}
+	 * and {@link #invokeQueryMethod(Method, MultiValueMap, Pageable, Sort)} using the given {@link Converter}s.
+	 * 
+	 * @author Oliver Gierke
+	 */
+	private static class UnwrappingRepositoryInvoker implements RepositoryInvoker {
+
+		private final RepositoryInvoker delegate;
+		private final Collection<Converter<Object, Object>> converters;
+
+		/**
+		 * Creates a new {@link UnwrappingRepositoryInvoker} for the given delegate and {@link Converter}s.
+		 * 
+		 * @param delegate must not be {@literal null}.
+		 * @param converters must not be {@literal null}.
+		 */
+		public UnwrappingRepositoryInvoker(RepositoryInvoker delegate, Collection<Converter<Object, Object>> converters) {
+
+			Assert.notNull(delegate, "Delegate RepositoryInvoker must not be null!");
+			Assert.notNull(converters, "Converters must not be null!");
+
+			this.delegate = delegate;
+			this.converters = converters;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeFindOne(java.io.Serializable)
+		 */
+		@SuppressWarnings("unchecked")
+		public <T> T invokeFindOne(Serializable id) {
+			return (T) postProcess(delegate.invokeFindOne(id));
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeQueryMethod(java.lang.reflect.Method, java.util.Map, org.springframework.data.domain.Pageable, org.springframework.data.domain.Sort)
+		 */
+		@Override
+		@SuppressWarnings("deprecation")
+		public Object invokeQueryMethod(Method method, Map<String, String[]> parameters, Pageable pageable, Sort sort) {
+			return postProcess(delegate.invokeQueryMethod(method, parameters, pageable, sort));
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeQueryMethod(java.lang.reflect.Method, org.springframework.util.MultiValueMap, org.springframework.data.domain.Pageable, org.springframework.data.domain.Sort)
+		 */
+		@Override
+		public Object invokeQueryMethod(Method method, MultiValueMap<String, ? extends Object> parameters,
+				Pageable pageable, Sort sort) {
+			return postProcess(delegate.invokeQueryMethod(method, parameters, pageable, sort));
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvocationInformation#hasDeleteMethod()
+		 */
+		@Override
+		public boolean hasDeleteMethod() {
+			return delegate.hasDeleteMethod();
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvocationInformation#hasFindAllMethod()
+		 */
+		@Override
+		public boolean hasFindAllMethod() {
+			return delegate.hasFindAllMethod();
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvocationInformation#hasFindOneMethod()
+		 */
+		@Override
+		public boolean hasFindOneMethod() {
+			return delegate.hasFindOneMethod();
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvocationInformation#hasSaveMethod()
+		 */
+		@Override
+		public boolean hasSaveMethod() {
+			return delegate.hasSaveMethod();
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeDelete(java.io.Serializable)
+		 */
+		@Override
+		public void invokeDelete(Serializable id) {
+			delegate.invokeDelete(id);
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeFindAll(org.springframework.data.domain.Pageable)
+		 */
+		@Override
+		public Iterable<Object> invokeFindAll(Pageable pageable) {
+			return delegate.invokeFindAll(pageable);
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeFindAll(org.springframework.data.domain.Sort)
+		 */
+		@Override
+		public Iterable<Object> invokeFindAll(Sort sort) {
+			return delegate.invokeFindAll(sort);
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.repository.support.RepositoryInvoker#invokeSave(java.lang.Object)
+		 */
+		@Override
+		public <T> T invokeSave(T object) {
+			return delegate.invokeSave(object);
+		}
+
+		/**
+		 * Invokes the configured converters for the given result.
+		 * 
+		 * @param result can be {@literal null}.
+		 * @return
+		 */
+		private Object postProcess(Object result) {
+
+			for (Converter<Object, Object> converter : converters) {
+				result = converter.convert(result);
+			}
+
+			return result;
+		}
+	}
+}

spring-data-rest-core/src/test/java/org/springframework/data/rest/core/support/UnwrappingRepositoryInvokerFactoryUnitTests.java

@@ -0,0 +1,105 @@
+/*
+ * Copyright 2015 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
+ *
+ *      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.springframework.data.rest.core.support;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Optional;
+
+import org.hamcrest.Matcher;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+import org.junit.runners.Parameterized.Parameters;
+import org.springframework.data.repository.support.RepositoryInvoker;
+import org.springframework.data.repository.support.RepositoryInvokerFactory;
+import org.springframework.util.LinkedMultiValueMap;
+
+/**
+ * Unit tests for {@link UnwrappingRepositoryInvokerFactory}.
+ * 
+ * @author Oliver Gierke
+ */
+@RunWith(Parameterized.class)
+public class UnwrappingRepositoryInvokerFactoryUnitTests {
+
+	static final Object REFERENCE = new Object();
+
+	RepositoryInvokerFactory delegate = mock(RepositoryInvokerFactory.class);
+	RepositoryInvoker invoker = mock(RepositoryInvoker.class);
+
+	RepositoryInvokerFactory factory;
+	Method method;
+
+	public @Parameter(value = 0) Object source;
+	public @Parameter(value = 1) Matcher<Object> value;
+
+	@Before
+	public void setUp() throws Exception {
+
+		when(delegate.getInvokerFor(Object.class)).thenReturn(invoker);
+
+		this.factory = new UnwrappingRepositoryInvokerFactory(delegate);
+		this.method = Object.class.getMethod("toString");
+	}
+
+	@Parameters
+	public static Collection<Object[]> data() {
+		return Arrays.asList(new Object[][] { //
+				{ Optional.empty(), is(nullValue()) }, //
+						{ Optional.of(REFERENCE), is(REFERENCE) }, //
+						{ com.google.common.base.Optional.absent(), is(nullValue()) }, //
+						{ com.google.common.base.Optional.of(REFERENCE), is(REFERENCE) } //
+				});
+	}
+
+	/**
+	 * @see DATAREST-511
+	 */
+	@Test
+	public void unwrapsValuesForFindOne() {
+		assertFindOneValueForSource(source, value);
+	}
+
+	/**
+	 * @see DATAREST-511
+	 */
+	@Test
+	public void unwrapsValuesForQuery() {
+		assertQueryValueForSource(source, value);
+	}
+
+	private void assertFindOneValueForSource(Object source, Matcher<Object> value) {
+
+		when(invoker.invokeFindOne(1L)).thenReturn(source);
+		assertThat(factory.getInvokerFor(Object.class).invokeFindOne(1L), value);
+	}
+
+	private void assertQueryValueForSource(Object source, Matcher<Object> value) {
+
+		when(invoker.invokeQueryMethod(method, new LinkedMultiValueMap<String, Object>(), null, null)).thenReturn(source);
+		assertThat(
+				factory.getInvokerFor(Object.class).invokeQueryMethod(method, new LinkedMultiValueMap<String, Object>(), null,
+						null), value);
+	}
+}

spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/config/RepositoryRestMvcConfiguration.java

@@ -65,6 +65,7 @@ import org.springframework.data.rest.core.mapping.ResourceDescription;
 import org.springframework.data.rest.core.mapping.ResourceMappings;
 import org.springframework.data.rest.core.support.DomainObjectMerger;
 import org.springframework.data.rest.core.support.RepositoryRelProvider;
+import org.springframework.data.rest.core.support.UnwrappingRepositoryInvokerFactory;
 import org.springframework.data.rest.webmvc.BasePathAwareController;
 import org.springframework.data.rest.webmvc.BasePathAwareHandlerMapping;
 import org.springframework.data.rest.webmvc.BaseUri;
@@ -575,7 +576,8 @@ public class RepositoryRestMvcConfiguration extends HateoasAwareSpringDataWebCon
 
 	@Bean
 	public RepositoryInvokerFactory repositoryInvokerFactory() {
-		return new DefaultRepositoryInvokerFactory(repositories(), defaultConversionService());
+		return new UnwrappingRepositoryInvokerFactory(new DefaultRepositoryInvokerFactory(repositories(),
+				defaultConversionService()));
 	}
 
 	@Bean

spring-data-rest-webmvc/src/test/java/org/springframework/data/rest/webmvc/TestMvcClient.java

@@ -20,6 +20,8 @@ import static org.junit.Assert.*;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
 
+import java.util.Arrays;
+import java.util.Iterator;
 import java.util.List;
 
 import org.springframework.hateoas.Link;
@@ -184,6 +186,27 @@ public class TestMvcClient {
 		return discover.get(0);
 	}
 
+	/**
+	 * Traverses the given link relations from the root.
+	 * 
+	 * @param rels
+	 * @return
+	 * @throws Exception
+	 */
+	public Link discoverUnique(String... rels) throws Exception {
+
+		Iterator<String> toTraverse = Arrays.asList(rels).iterator();
+		Link lastLink = null;
+
+		while (toTraverse.hasNext()) {
+
+			String rel = toTraverse.next();
+			lastLink = lastLink == null ? discoverUnique(rel) : discoverUnique(lastLink, rel);
+		}
+
+		return lastLink;
+	}
+
 	/**
 	 * Given a URI (root), discover the URIs for a given rel.
 	 *

spring-data-rest-webmvc/src/test/java/org/springframework/data/rest/webmvc/mongodb/MongoWebTests.java

@@ -301,4 +301,18 @@ public class MongoWebTests extends CommonWebTests {
 				andExpect(status().isNotModified()).//
 				andExpect(header().string(ETAG, is(notNullValue())));
 	}
+
+	/**
+	 * @see DATAREST-511
+	 */
+	@Test
+	public void invokesQueryResourceReturningAnOptional() throws Exception {
+
+		Profile profile = repository.findAll().iterator().next();
+
+		Link link = client.discoverUnique("profiles", "search", "findById");
+
+		mvc.perform(get(link.expand(profile.getId()).getHref())).//
+				andExpect(status().isOk());
+	}
 }

spring-data-rest-webmvc/src/test/java/org/springframework/data/rest/webmvc/mongodb/ProfileRepository.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -16,6 +16,7 @@
 package org.springframework.data.rest.webmvc.mongodb;
 
 import java.util.List;
+import java.util.Optional;
 
 import org.springframework.data.repository.PagingAndSortingRepository;
 import org.springframework.data.repository.query.Param;
@@ -32,4 +33,9 @@ public interface ProfileRepository extends PagingAndSortingRepository<Profile, S
 	 * @see DATAREST-247
 	 */
 	long countByType(@Param("type") String type);
+
+	/**
+	 * @see DATAREST-511
+	 */
+	Optional<Profile> findById(@Param("id") String id);
 }