DATAREST-160 - Added support for ETag/If-Match based on entity's version property.

Original pull request: #148.

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

@@ -46,7 +46,9 @@ import org.springframework.data.rest.core.mapping.SearchResourceMappings;
 import org.springframework.data.rest.core.mapping.SupportedHttpMethods;
 import org.springframework.data.rest.webmvc.support.BackendId;
 import org.springframework.data.rest.webmvc.support.DefaultedPageable;
+import org.springframework.data.rest.webmvc.support.IfMatch;
 import org.springframework.data.rest.webmvc.support.RepositoryEntityLinks;
+import org.springframework.data.rest.webmvc.support.EtagValidator;
 import org.springframework.data.web.PagedResourcesAssembler;
 import org.springframework.hateoas.Link;
 import org.springframework.hateoas.PagedResources;
@@ -60,6 +62,7 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.HttpRequestMethodNotSupportedException;
+import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.ResponseBody;
@@ -81,19 +84,21 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 	private final RepositoryEntityLinks entityLinks;
 	private final RepositoryRestConfiguration config;
 	private final ConversionService conversionService;
+	private final EtagValidator etagValidator;
 
 	private ApplicationEventPublisher publisher;
 
 	@Autowired
 	public RepositoryEntityController(Repositories repositories, RepositoryRestConfiguration config,
 			RepositoryEntityLinks entityLinks, PagedResourcesAssembler<Object> assembler,
-			@Qualifier("defaultConversionService") ConversionService conversionService) {
+			@Qualifier("defaultConversionService") ConversionService conversionService, EtagValidator etagValidator) {
 
 		super(assembler);
 
 		this.entityLinks = entityLinks;
 		this.config = config;
 		this.conversionService = conversionService;
+		this.etagValidator = etagValidator;
 	}
 
 	/*
@@ -295,12 +300,17 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 			return new ResponseEntity<Resource<?>>(HttpStatus.NOT_FOUND);
 		}
 
-		return new ResponseEntity<Resource<?>>(assembler.toFullResource(domainObj), HttpStatus.OK);
+		PersistentEntityResource persistentEntityResource = assembler.toFullResource(domainObj);
+		HttpHeaders httpHeaders = new HttpHeaders();
+		etagValidator.addEtagHeader(httpHeaders, persistentEntityResource);
+
+		return new ResponseEntity<Resource<?>>(persistentEntityResource, httpHeaders, HttpStatus.OK);
 	}
 
 	/**
 	 * <code>PUT /{repository}/{id}</code> - Updates an existing entity or creates one at exactly that place.
-	 * 
+	 *
+	 * @param eTagMatch
 	 * @param resourceInformation
 	 * @param payload
 	 * @param id
@@ -308,9 +318,8 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 	 * @throws HttpRequestMethodNotSupportedException
 	 */
 	@RequestMapping(value = BASE_MAPPING + "/{id}", method = RequestMethod.PUT)
-	public ResponseEntity<? extends ResourceSupport> putItemResource(RootResourceInformation resourceInformation,
-			PersistentEntityResource payload, @BackendId Serializable id, PersistentEntityResourceAssembler assembler)
-			throws HttpRequestMethodNotSupportedException {
+	public ResponseEntity<? extends ResourceSupport> putItemResource(RootResourceInformation resourceInformation, PersistentEntityResource payload, @BackendId Serializable id,
+			PersistentEntityResourceAssembler assembler, @IfMatch String eTagMatch) throws HttpRequestMethodNotSupportedException {
 
 		resourceInformation.verifySupportedMethod(HttpMethod.PUT, ResourceType.ITEM);
 
@@ -322,13 +331,19 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 		RepositoryInvoker invoker = resourceInformation.getInvoker();
 		Object objectToSave = incomingWrapper.getBean();
 
-		return invoker.invokeFindOne(id) == null ? createAndReturn(objectToSave, invoker, assembler) : saveAndReturn(
-				objectToSave, invoker, PUT, assembler);
+		Object domainObject = invoker.invokeFindOne(id);
+		if (domainObject != null) {
+			etagValidator.validateEtag(eTagMatch, resourceInformation, domainObject);
+		}
+
+		return domainObject == null ? createAndReturn(objectToSave, invoker, assembler) : saveAndReturn(objectToSave,
+				invoker, PUT, assembler);
 	}
 
 	/**
 	 * <code>PUT /{repository}/{id}</code> - Updates an existing entity or creates one at exactly that place.
-	 * 
+	 *
+	 * @param eTagMatch
 	 * @param resourceInformation
 	 * @param payload
 	 * @param id
@@ -337,22 +352,27 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 	 * @throws ResourceNotFoundException
 	 */
 	@RequestMapping(value = BASE_MAPPING + "/{id}", method = RequestMethod.PATCH)
-	public ResponseEntity<ResourceSupport> patchItemResource(RootResourceInformation resourceInformation,
-			PersistentEntityResource payload, @BackendId Serializable id, PersistentEntityResourceAssembler assembler)
-			throws HttpRequestMethodNotSupportedException, ResourceNotFoundException {
+	public ResponseEntity<ResourceSupport> patchItemResource(RootResourceInformation resourceInformation, PersistentEntityResource payload, @BackendId Serializable id,
+			PersistentEntityResourceAssembler assembler, @IfMatch String eTagMatch) throws HttpRequestMethodNotSupportedException,
+			ResourceNotFoundException {
 
 		resourceInformation.verifySupportedMethod(HttpMethod.PATCH, ResourceType.ITEM);
 
-		if (resourceInformation.getInvoker().invokeFindOne(id) == null) {
+		Object domainObject = resourceInformation.getInvoker().invokeFindOne(id);
+
+		if (domainObject == null) {
 			throw new ResourceNotFoundException();
 		}
 
+		etagValidator.validateEtag(eTagMatch, resourceInformation, domainObject);
+
 		return saveAndReturn(payload.getContent(), resourceInformation.getInvoker(), PATCH, assembler);
 	}
 
 	/**
 	 * <code>DELETE /{repository}/{id}</code> - Deletes the entity backing the item resource.
-	 * 
+	 *
+	 * @param eTagMatch
 	 * @param resourceInformation
 	 * @param id
 	 * @return
@@ -360,7 +380,7 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 	 * @throws HttpRequestMethodNotSupportedException
 	 */
 	@RequestMapping(value = BASE_MAPPING + "/{id}", method = RequestMethod.DELETE)
-	public ResponseEntity<?> deleteItemResource(RootResourceInformation resourceInformation, @BackendId Serializable id)
+	public ResponseEntity<?> deleteItemResource(RootResourceInformation resourceInformation, @BackendId Serializable id, @IfMatch String eTagMatch) 
 			throws ResourceNotFoundException, HttpRequestMethodNotSupportedException {
 
 		resourceInformation.verifySupportedMethod(HttpMethod.DELETE, ResourceType.ITEM);
@@ -372,6 +392,8 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 			throw new ResourceNotFoundException();
 		}
 
+		etagValidator.validateEtag(eTagMatch, resourceInformation, domainObj);
+
 		publisher.publishEvent(new BeforeDeleteEvent(domainObj));
 		invoker.invokeDelete(id);
 		publisher.publishEvent(new AfterDeleteEvent(domainObj));
@@ -381,8 +403,7 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 
 	/**
 	 * Merges the given incoming object into the given domain object.
-	 * 
-	 * @param incoming
+	 *
 	 * @param domainObject
 	 * @param invoker
 	 * @param httpMethod
@@ -402,7 +423,11 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 		}
 
 		if (config.isReturnBodyOnUpdate()) {
-			return ControllerUtils.toResponseEntity(HttpStatus.OK, headers, assembler.toFullResource(obj));
+
+			PersistentEntityResource persistentEntityResource = assembler.toFullResource(obj);
+			etagValidator.addEtagHeader(headers, persistentEntityResource);
+
+			return ControllerUtils.toResponseEntity(HttpStatus.OK, headers, persistentEntityResource);
 		} else {
 			return ControllerUtils.toEmptyResponse(HttpStatus.NO_CONTENT, headers);
 		}
@@ -426,6 +451,11 @@ class RepositoryEntityController extends AbstractRepositoryRestController implem
 		addLocationHeader(headers, assembler, savedObject);
 
 		PersistentEntityResource resource = config.isReturnBodyOnCreate() ? assembler.toFullResource(savedObject) : null;
+
+		if (resource != null) {
+			etagValidator.addEtagHeader(headers, resource);
+		}
+
 		return ControllerUtils.toResponseEntity(HttpStatus.CREATED, headers, resource);
 	}
 

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

@@ -89,8 +89,10 @@ import org.springframework.data.rest.webmvc.spi.BackendIdConverter.DefaultIdConv
 import org.springframework.data.rest.webmvc.support.BackendIdHandlerMethodArgumentResolver;
 import org.springframework.data.rest.webmvc.support.DefaultedPageableHandlerMethodArgumentResolver;
 import org.springframework.data.rest.webmvc.support.HttpMethodHandlerMethodArgumentResolver;
+import org.springframework.data.rest.webmvc.support.IfMatchHeaderArgumentResolver;
 import org.springframework.data.rest.webmvc.support.JpaHelper;
 import org.springframework.data.rest.webmvc.support.RepositoryEntityLinks;
+import org.springframework.data.rest.webmvc.support.EtagValidator;
 import org.springframework.data.util.AnnotatedTypeScanner;
 import org.springframework.data.web.HateoasPageableHandlerMethodArgumentResolver;
 import org.springframework.data.web.HateoasSortHandlerMethodArgumentResolver;
@@ -306,6 +308,10 @@ public class RepositoryRestMvcConfiguration extends HateoasAwareSpringDataWebCon
 				resourceMetadataHandlerMethodArgumentResolver(), baseUri());
 	}
 
+	@Bean
+	public IfMatchHeaderArgumentResolver ifMatchHeaderArgumentResolver(){
+		return new IfMatchHeaderArgumentResolver();
+	}
 	/**
 	 * A special {@link org.springframework.hateoas.EntityLinks} implementation that takes repository and current
 	 * configuration into account when generating links.
@@ -615,6 +621,11 @@ public class RepositoryRestMvcConfiguration extends HateoasAwareSpringDataWebCon
 		return OrderAwarePluginRegistry.create(converters);
 	}
 
+	@Bean
+	public EtagValidator etagValidator() {
+		return new EtagValidator(defaultConversionService());
+	}
+
 	private List<HandlerMethodArgumentResolver> defaultMethodArgumentResolvers() {
 
 		PersistentEntityResourceAssemblerArgumentResolver peraResolver = new PersistentEntityResourceAssemblerArgumentResolver(
@@ -628,7 +639,7 @@ public class RepositoryRestMvcConfiguration extends HateoasAwareSpringDataWebCon
 		return Arrays.asList(defaultedPageableResolver, pageableResolver, sortResolver(),
 				serverHttpRequestMethodArgumentResolver(), repoRequestArgumentResolver(), persistentEntityArgumentResolver(),
 				resourceMetadataHandlerMethodArgumentResolver(), HttpMethodHandlerMethodArgumentResolver.INSTANCE,
-				peraResolver, backendIdHandlerMethodArgumentResolver());
+				peraResolver, backendIdHandlerMethodArgumentResolver(), ifMatchHeaderArgumentResolver());
 	}
 
 	@Autowired GeoModule geoModule;

spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/support/EtagValidator.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright 2014 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.webmvc.support;
+
+import org.springframework.core.convert.ConversionService;
+import org.springframework.dao.OptimisticLockingFailureException;
+import org.springframework.data.mapping.PersistentEntity;
+import org.springframework.data.mapping.model.BeanWrapper;
+import org.springframework.data.rest.webmvc.PersistentEntityResource;
+import org.springframework.data.rest.webmvc.RootResourceInformation;
+import org.springframework.http.HttpHeaders;
+import org.springframework.util.Assert;
+import org.springframework.web.bind.annotation.ValueConstants;
+
+/**
+ * An ETag validator that verifies concurrency issues and the validity of the Etag/ If-Match header values to implement
+ * optimistic locking.
+ * 
+ * @author Pablo Lozano
+ */
+
+public class EtagValidator {
+
+	private final ConversionService conversionService;
+
+	public EtagValidator(ConversionService conversionService) {
+		this.conversionService = conversionService;
+		Assert.notNull(conversionService, "Conversion service must not be null");
+	}
+
+	/**
+	 * Compares the given eTag with the entity's version property, if there are different an
+	 * OptimisticLockingFailureException is thrown.
+	 *
+	 * @param requestEtag
+	 * @param resourceInformation
+	 * @param domainObject
+	 * @return
+	 */
+	public void validateEtag(String requestEtag, RootResourceInformation resourceInformation, Object domainObject) {
+
+		if (requestEtag != null && !requestEtag.equals(ValueConstants.DEFAULT_NONE)) {
+			final String entityEtag = getVersionInformation(resourceInformation.getPersistentEntity(), domainObject);
+			if (!requestEtag.equals(entityEtag)) {
+				throw new OptimisticLockingFailureException("Invalid If-Match version provided, the resource has gone thru"
+						+ " changes after resource's request");
+			}
+		}
+	}
+
+	/**
+	 * Sets the Etag to the header, if the domain object does not contain a Version property it will return and leave the
+	 * headers as is.
+	 *
+	 * @param headers
+	 * @param persistentEntityResource
+	 */
+	public void addEtagHeader(HttpHeaders headers, PersistentEntityResource persistentEntityResource) {
+
+		String version = getVersionInformation(persistentEntityResource.getPersistentEntity(),
+				persistentEntityResource.getContent());
+		if (version != null) {
+			headers.setETag(version);
+		}
+	}
+
+	/**
+	 * Returns the quoted version property of a domain object, returns null if it doesn't contains the property
+	 *
+	 * @param persistentEntity
+	 * @param domainObject
+	 * @return
+	 */
+	@SuppressWarnings("rawtypes")
+	private String getVersionInformation(PersistentEntity persistentEntity, Object domainObject) {
+
+		if (persistentEntity.hasVersionProperty()) {
+
+			BeanWrapper<Object> beanWrapper = BeanWrapper.create(domainObject, conversionService);
+			Object version = beanWrapper.getProperty(persistentEntity.getVersionProperty());
+			return "\"" + version.toString() + "\"";
+		}
+		return null;
+	}
+	
+}

spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/support/IfMatch.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2014 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.webmvc.support;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.web.bind.annotation.ValueConstants;
+
+/**
+ * Annotation to find the If-Match header of a request
+ * 
+ * @author Pablo Lozano
+ */
+
+@Target(ElementType.PARAMETER)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface IfMatch {
+
+	String defaultValue() default ValueConstants.DEFAULT_NONE;
+}

spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/support/IfMatchHeaderArgumentResolver.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2014 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.webmvc.support;
+
+import javax.servlet.http.HttpServletRequest;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.web.bind.support.WebDataBinderFactory;
+import org.springframework.web.context.request.NativeWebRequest;
+import org.springframework.web.method.support.HandlerMethodArgumentResolver;
+import org.springframework.web.method.support.ModelAndViewContainer;
+
+/**
+ * {@link HandlerMethodArgumentResolver} to resolve If-Match headers for optimistic locking handling {@link IfMatch}.
+ * 
+ * @author Pablo Lozano
+ */
+public class IfMatchHeaderArgumentResolver implements HandlerMethodArgumentResolver {
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.web.method.support.HandlerMethodArgumentResolver#supportsParameter(org.springframework.core.MethodParameter)
+	 */
+	@Override
+	public boolean supportsParameter(MethodParameter parameter) {
+		return parameter.hasParameterAnnotation(IfMatch.class);
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.web.method.support.HandlerMethodArgumentResolver#resolveArgument(org.springframework.core.MethodParameter, org.springframework.web.method.support.ModelAndViewContainer, org.springframework.web.context.request.NativeWebRequest, org.springframework.web.bind.support.WebDataBinderFactory)
+	 */
+	@Override
+	public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
+			NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception {
+
+		IfMatch ifMatchHeader = parameter.getParameterAnnotation(IfMatch.class);
+		HttpServletRequest httprequest = (HttpServletRequest) webRequest.getNativeRequest();
+		Object result = httprequest.getHeader("If-Match");
+
+		if (result == null) {
+			result = ifMatchHeader.defaultValue();
+		}
+		return result;
+	}
+}

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

@@ -62,12 +62,13 @@ public class RepositoryControllerIntegrationTests extends AbstractControllerInte
 
 		RepositoryLinksResource resource = controller.listRepositories().getBody();
 
-		assertThat(resource.getLinks(), hasSize(5));
+		assertThat(resource.getLinks(), hasSize(6));
 
 		assertThat(resource.hasLink("people"), is(true));
 		assertThat(resource.hasLink("orders"), is(true));
 		assertThat(resource.hasLink("addresses"), is(true));
 		assertThat(resource.hasLink("books"), is(true));
 		assertThat(resource.hasLink("authors"), is(true));
+		assertThat(resource.hasLink("receipts"), is(true));
 	}
 }

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

@@ -89,7 +89,7 @@ public class RepositoryEntityControllerIntegrationTests extends AbstractControll
 		PersistentEntityResource persistentEntityResource = PersistentEntityResource.build(new Order(new Person()),
 				entities.getPersistentEntity(Order.class)).build();
 
-		ResponseEntity<?> entity = controller.putItemResource(information, persistentEntityResource, 1L, assembler);
+		ResponseEntity<?> entity = controller.putItemResource(information, persistentEntityResource, 1L, assembler, null);
 
 		assertThat(entity.getHeaders().getLocation().toString(), not(endsWith("{?projection}")));
 	}

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

@@ -21,6 +21,7 @@ import static org.springframework.data.rest.webmvc.util.TestUtils.*;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
 
+import java.math.BigDecimal;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -581,6 +582,38 @@ public class JpaWebTests extends CommonWebTests {
 				andExpect(jsonPath("$._embedded.books[1].title").value("Spring Data (Second Edition)"));
 	}
 
+	/**
+	 * @see DATAREST-160
+	 */
+	@Test
+	public void returnConflictWhenConcurrentlyEditingVersionedEntity() throws Exception {
+
+		Link receiptLink = client.discoverUnique("receipts");
+
+		Receipt receipt = new Receipt();
+		receipt.setAmount(new BigDecimal(50));
+		receipt.setSaleItem("Springy Tacos");
+
+		String stringReceipt = mapper.writeValueAsString(receipt);
+
+		MockHttpServletResponse createdReceipt = postAndGet(receiptLink, stringReceipt, MediaType.APPLICATION_JSON);
+		Link tacosLink = client.assertHasLinkWithRel("self", createdReceipt);
+		assertJsonPathEquals("$.saleItem", "Springy Tacos", createdReceipt);
+
+		UriComponentsBuilder builder = UriComponentsBuilder.fromUriString(tacosLink.getHref());
+		String concurrencyTag = createdReceipt.getHeader("ETag");
+
+		mvc.perform(
+				patch(builder.build().toUriString()).content("{ \"saleItem\" : \"SpringyBurritos\" }")
+						.contentType(MediaType.APPLICATION_JSON).header("If-Match", concurrencyTag)).andExpect(
+				status().isNoContent());
+
+		mvc.perform(
+				patch(builder.build().toUriString()).content("{ \"saleItem\" : \"SpringyTequila\" }")
+						.contentType(MediaType.APPLICATION_JSON).header("If-Match", "\"falseETag\"")).andExpect(
+				status().isConflict());
+	}
+
 	/**
 	 * Asserts the {@link Person} resource the given link points to contains siblings with the given names.
 	 * 

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

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2014 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.webmvc.jpa;
+
+import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
+
+import javax.persistence.*;
+import javax.persistence.Entity;
+import java.math.BigDecimal;
+import java.util.Date;
+
+/**
+ * An entity that represents a receipt.
+ *
+ * @author Pablo Lozano
+ */
+@Entity
+@JsonIgnoreProperties({"version"})
+public class Receipt {
+
+    @Id
+    @GeneratedValue
+    private Long id;
+
+    private String saleItem;
+
+    private BigDecimal amount;
+
+    @Version
+    @Temporal(TemporalType.TIMESTAMP)
+    private Date version;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getSaleItem() {
+        return saleItem;
+    }
+
+    public void setSaleItem(String saleItem) {
+        this.saleItem = saleItem;
+    }
+
+    public BigDecimal getAmount() {
+        return amount;
+    }
+
+    public void setAmount(BigDecimal amount) {
+        this.amount = amount;
+    }
+
+
+    public Date getVersion() {
+        return version;
+    }
+
+    public void setVersion(Date version) {
+        this.version = version;
+    }
+}

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

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2014 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.webmvc.jpa;
+
+import org.springframework.data.repository.CrudRepository;
+
+/**
+ * A repository to manage {@link Receipt}s.
+ *
+ * @author Pablo Lozano
+ */
+
+public interface ReceiptRepository extends CrudRepository<Receipt, Long> {
+
+}

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

@@ -18,9 +18,12 @@ package org.springframework.data.rest.webmvc.mongodb;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
 
+import java.math.BigDecimal;
 import java.util.Arrays;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -33,6 +36,7 @@ import org.springframework.mock.web.MockHttpServletResponse;
 import org.springframework.test.context.ContextConfiguration;
 
 import com.jayway.jsonpath.JsonPath;
+import org.springframework.web.util.UriComponentsBuilder;
 
 /**
  * Integration tests for MongoDB repositories.
@@ -46,6 +50,8 @@ public class MongoWebTests extends CommonWebTests {
 	@Autowired ProfileRepository repository;
 	@Autowired UserRepository userRepository;
 
+    ObjectMapper mapper = new ObjectMapper();
+
 	@Before
 	public void populateProfiles() {
 
@@ -148,4 +154,35 @@ public class MongoWebTests extends CommonWebTests {
 		assertThat(JsonPath.read(response.getContentAsString(), "$.lastname"), is(nullValue()));
 		assertThat(JsonPath.read(response.getContentAsString(), "$.address.zipCode"), is((Object) "ZIP"));
 	}
+
+	/**
+	 * @see DATAREST-160
+	 */
+	@Test
+	public void returnConflictWhenConcurrentlyEditingVersionedEntity() throws Exception {
+		Link receiptLink = discoverUnique("receipts");
+
+		Receipt receipt = new Receipt();
+		receipt.setAmount(new BigDecimal(50));
+		receipt.setSaleItem("Springy Tacos");
+
+		String stringReceipt = mapper.writeValueAsString(receipt);
+
+		MockHttpServletResponse createdReceipt = postAndGet(receiptLink, stringReceipt, MediaType.APPLICATION_JSON);
+		Link tacosLink = assertHasLinkWithRel("self", createdReceipt);
+		assertJsonPathEquals("$.saleItem", "Springy Tacos", createdReceipt);
+
+		UriComponentsBuilder builder = UriComponentsBuilder.fromUriString(tacosLink.getHref());
+		String concurrencyTag = createdReceipt.getHeader("ETag");
+
+		mvc.perform(
+				patch(builder.build().toUriString()).content("{ \"saleItem\" : \"SpringyBurritos\" }")
+						.contentType(MediaType.APPLICATION_JSON).header("If-Match", concurrencyTag)).andExpect(
+				status().isNoContent());
+
+		mvc.perform(
+				patch(builder.build().toUriString()).content("{ \"saleItem\" : \"SpringyTequila\" }")
+						.contentType(MediaType.APPLICATION_JSON).header("If-Match", concurrencyTag)).andExpect(
+				status().isConflict());
+	}
 }

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

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2014 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.webmvc.mongodb;
+
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.annotation.Version;
+import org.springframework.data.mongodb.core.mapping.Document;
+
+import java.math.BigDecimal;
+
+
+/**
+ * @author Pablo Lozano
+ */
+@Document
+public class Receipt {
+
+    @Id
+    public String id;
+
+    private String saleItem;
+
+    private BigDecimal amount;
+
+    @Version
+    private Long version;
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public String getSaleItem() {
+        return saleItem;
+    }
+
+    public void setSaleItem(String saleItem) {
+        this.saleItem = saleItem;
+    }
+
+    public BigDecimal getAmount() {
+        return amount;
+    }
+
+    public void setAmount(BigDecimal amount) {
+        this.amount = amount;
+    }
+
+    public Long getVersion() {
+        return version;
+    }
+
+    public void setVersion(Long version) {
+        this.version = version;
+    }
+}

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

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2014 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.webmvc.mongodb;
+
+import org.springframework.data.repository.CrudRepository;
+
+/**
+ * A repository to manage {@link Receipt}s.
+ *
+ * @author Pablo Lozano
+ */
+
+public interface ReceiptRepository extends CrudRepository<Receipt, String> {
+
+}

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

@@ -0,0 +1,120 @@
+/*
+ * Copyright 2014 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.webmvc.support;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+import javax.persistence.Version;
+import javax.persistence.metamodel.Metamodel;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.springframework.dao.OptimisticLockingFailureException;
+import org.springframework.data.jpa.mapping.JpaMetamodelMappingContext;
+import org.springframework.data.jpa.mapping.JpaPersistentEntity;
+import org.springframework.data.rest.core.mapping.MappingResourceMetadata;
+import org.springframework.data.rest.core.mapping.ResourceMetadata;
+import org.springframework.data.rest.webmvc.PersistentEntityResource;
+import org.springframework.data.rest.webmvc.RootResourceInformation;
+import org.springframework.format.support.DefaultFormattingConversionService;
+import org.springframework.http.HttpHeaders;
+
+/**
+ * Tests for the EtagValidator used for optimistic locking
+ * 
+ * @author Pablo Lozano
+ */
+
+@RunWith(MockitoJUnitRunner.class)
+public class EtagValidatorTests {
+
+	EtagValidator etagValidator;
+
+	@Mock Metamodel model;
+
+	JpaMetamodelMappingContext context;
+	JpaPersistentEntity<?> entity;
+
+	@Before
+	public void setUp() {
+		context = new JpaMetamodelMappingContext(model);
+		entity = context.getPersistentEntity(Sample.class);
+		etagValidator = new EtagValidator(new DefaultFormattingConversionService());
+	}
+
+	/**
+	 * @see DATAREST-160
+	 */
+	@Test(expected = OptimisticLockingFailureException.class)
+	public void expectWrongEtag() throws Exception {
+		Sample sampleEntity = new Sample();
+		sampleEntity.version = 0;
+
+		ResourceMetadata resourceMetadata = new MappingResourceMetadata(entity);
+		RootResourceInformation rootResourceInformation = new RootResourceInformation(resourceMetadata, entity, null);
+
+		etagValidator.validateEtag("\"1\"", rootResourceInformation, sampleEntity);
+	}
+
+	/**
+	 * @see DATAREST-160
+	 */
+	@Test
+	public void expectCorrectEtag() throws Exception {
+		Sample sampleEntity = new Sample();
+		sampleEntity.version = 0;
+
+		ResourceMetadata resourceMetadata = new MappingResourceMetadata(entity);
+		RootResourceInformation rootResourceInformation = new RootResourceInformation(resourceMetadata, entity, null);
+
+		etagValidator.validateEtag("\"0\"", rootResourceInformation, sampleEntity);
+	}
+
+	/**
+	 * @see DATAREST-160
+	 */
+	@Test
+	public void setCorrectEtagHeader() throws Exception {
+		Sample sampleEntity = new Sample();
+		sampleEntity.version = 0;
+
+		HttpHeaders headers = new HttpHeaders();
+		PersistentEntityResource perf = PersistentEntityResource.build(sampleEntity, entity).build();
+		etagValidator.addEtagHeader(headers, perf);
+		Object ifMatch = headers.getETag();
+
+		assertThat(ifMatch, is((Object) "\"0\""));
+	}
+
+	public class Sample {
+
+		private @Version long version;
+
+		public long getVersion() {
+			return version;
+		}
+
+		public void setVersion(long version) {
+			this.version = version;
+		}
+
+	}
+}