DATAREST-1213 - ETag creation now uses proxy target for projections.

Original pull request: #355.

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

@@ -37,6 +37,7 @@ import org.springframework.util.Assert;
  * instances.
  *
  * @author Oliver Gierke
+ * @author Dario Seidl
  * @soundtrack Ron Spielman Trio - Matchstick
  */
 @RequiredArgsConstructor
@@ -59,7 +60,7 @@ public class HttpHeadersPreparer {
 	public HttpHeaders prepareHeaders(Optional<PersistentEntityResource> resource) {
 
 		return resource//
-				.map(it -> prepareHeaders(it.getPersistentEntity(), it.getContent()))//
+				.map(it -> prepareHeaders(it.getPersistentEntity(), it.getTargetEntity()))//
 				.orElseGet(() -> new HttpHeaders());
 	}
 
@@ -75,6 +76,8 @@ public class HttpHeadersPreparer {
 
 		Assert.notNull(entity, "PersistentEntity must not be null!");
 		Assert.notNull(value, "Entity value must not be null!");
+		Assert.isInstanceOf(entity.getType(), value, () ->
+			String.format("Target bean of type %s is not of type of the persistent entity (%s)!", value.getClass().getName(), entity.getType().getName()));
 
 		// Add ETag
 		HttpHeaders headers = ETag.from(entity, value).addTo(new HttpHeaders());

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

@@ -24,6 +24,7 @@ import java.util.List;
 import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
+import org.springframework.data.projection.TargetAware;
 import org.springframework.hateoas.CollectionModel;
 import org.springframework.hateoas.EntityModel;
 import org.springframework.hateoas.Link;
@@ -38,6 +39,7 @@ import com.fasterxml.jackson.annotation.JsonIgnore;
  *
  * @author Jon Brisbin
  * @author Oliver Gierke
+ * @author Dario Seidl
  */
 public class PersistentEntityResource extends EntityModel<Object> {
 
@@ -88,13 +90,27 @@ public class PersistentEntityResource extends EntityModel<Object> {
 		return entity;
 	}
 
+	/**
+	 * Returns the underlying instance. If the instance is a dynamic JDK proxy, the proxy target is returned.
+	 *
+	 * @return
+	 */
+	public Object getTargetEntity() {
+		Object content = getContent();
+		if (content instanceof TargetAware) {
+			return ((TargetAware) content).getTarget();
+		} else {
+			return content;
+		}
+	}
+
 	/**
 	 * Returns the {@link PersistentPropertyAccessor} for the underlying content bean.
 	 *
 	 * @return
 	 */
 	public PersistentPropertyAccessor<?> getPropertyAccessor() {
-		return entity.getPropertyAccessor(getContent());
+		return entity.getPropertyAccessor(getTargetEntity());
 	}
 
 	/**

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

@@ -32,6 +32,7 @@ import org.springframework.util.Assert;
  * A value object to represent ETags.
  *
  * @author Oliver Gierke
+ * @author Dario Seidl
  */
 @EqualsAndHashCode
 public final class ETag {
@@ -74,7 +75,7 @@ public final class ETag {
 
 		Assert.notNull(resource, "PersistentEntityResource must not be null!");
 
-		return from(resource.getPersistentEntity(), resource.getContent());
+		return from(resource.getPersistentEntity(), resource.getTargetEntity());
 	}
 
 	/**