Return 400 Bad Request when request body converter returns incompatible type

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

@@ -63,6 +63,7 @@
  * @author Jon Brisbin
  * @author Oliver Gierke
  * @author Mark Paluch
+ * @author Babalola Opeyemi Daniel
  */
 public class PersistentEntityResourceHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {
 
@@ -139,6 +140,10 @@ public boolean supportsParameter(MethodParameter parameter) {
 				throw new HttpMessageNotReadableException(String.format(ERROR_MESSAGE, domainType), request);
 			}
 
+			if (!domainType.isInstance(newObject)) {
+				throw new HttpMessageNotReadableException(String.format(ERROR_MESSAGE, domainType), request);
+			}
+
 			PersistentEntity<?, ?> entity = resourceInformation.getPersistentEntity();
 
 			if (!id.isPresent()) {

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

@@ -42,7 +42,9 @@
 import org.springframework.data.rest.webmvc.support.BackendIdHandlerMethodArgumentResolver;
 import org.springframework.http.HttpInputMessage;
 import org.springframework.http.MediaType;
+import org.springframework.hateoas.CollectionModel;
 import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.plugin.core.PluginRegistry;
 import org.springframework.web.bind.support.WebDataBinderFactory;
@@ -55,6 +57,7 @@
  * Unit tests for {@link PersistentEntityResourceHandlerMethodArgumentResolver}.
  *
  * @author Oliver Gierke
+ * @author Babalola Opeyemi Daniel
  */
 class PersistentEntityResourceHandlerMethodArgumentResolverUnitTests {
 
@@ -124,6 +127,23 @@ Arrays.<HttpMessageConverter<?>> asList(converter), rootResourceResolver, backen
 		});
 	}
 
+	@Test // GH-1194
+	@SuppressWarnings("unchecked")
+	void rejectsRequestBodyIfConverterReturnsIncompatibleType() throws Exception {
+
+		PersistentEntityResourceHandlerMethodArgumentResolver argumentResolver = new PersistentEntityResourceHandlerMethodArgumentResolver(
+				Arrays.<HttpMessageConverter<?>> asList(converter), rootResourceResolver, backendIdResolver, reader,
+				PluginRegistry.empty(), FACTORY);
+
+		HttpServletRequest request = new MockHttpServletRequest("POST", "/foo");
+
+		doReturn(CollectionModel.empty()).when(converter).read(Mockito.any(Class.class), Mockito.any(HttpInputMessage.class));
+
+		assertThatExceptionOfType(HttpMessageNotReadableException.class).isThrownBy(() -> {
+			argumentResolver.resolveArgument(null, null, new ServletWebRequest(request), null);
+		});
+	}
+
 	private void setupRootResourceInfoFor(Class<?> type) throws Exception {
 
 		RootResourceInformation information = mock(RootResourceInformation.class);