Properly deep-merge nested documents on PUT.

This is needed to consider read-only properties within those objects as those would otherwise get overridden.

Fixes: #2174

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

@@ -40,6 +40,7 @@
 import org.springframework.data.rest.webmvc.mapping.Associations;
 import org.springframework.data.rest.webmvc.util.InputStreamHttpInputMessage;
 import org.springframework.data.util.ClassTypeInformation;
+import org.springframework.data.util.Optionals;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.lang.Nullable;
@@ -61,6 +62,7 @@
  * @author Craig Andrews
  * @author Mathias Düsterhöft
  * @author Thomas Mrozinski
+ * @author Lars Vierbergen
  * @since 2.2
  */
 public class DomainObjectReader {
@@ -678,7 +680,7 @@ public void doWithPersistentProperty(PersistentProperty<?> property) {
 			} else if (property.isCollectionLike()) {
 				result = mergeCollections(property, sourceValue, targetValue, mapper);
 			} else if (property.isEntity()) {
-				result = mergeForPut(sourceValue, targetValue, mapper);
+				result = Optionals.mapIfAllPresent(sourceValue, targetValue, (l, r) -> mergeForPut(l, r, mapper));
 			} else {
 				result = sourceValue;
 			}

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

@@ -618,6 +618,33 @@ void writesPolymorphicArrayWithSwitchedItemForPut() throws Exception {
 		});
 	}
 
+	@Test // #2174
+	void nestedEntitiesWithReadonlyFieldAreKeptForPut() throws Exception {
+
+		Inner inner = new Inner();
+		inner.name = "inner name";
+		inner.prop = "something";
+		inner.readOnly = "readonly value";
+		inner.hidden = "hidden value";
+
+		Outer outer = new Outer();
+		outer.prop = "else";
+		outer.name = "outer name";
+		outer.inner = inner;
+
+		JsonNode node = new ObjectMapper().readTree("{ \"inner\" : { \"name\" : \"new inner name\" } }");
+
+		Outer result = reader.readPut((ObjectNode) node, outer, new ObjectMapper());
+
+		assertThat(result).isSameAs(outer);
+		assertThat(result.prop).isNull();
+		assertThat(result.inner.prop).isNull();
+		assertThat(result.inner.name).isEqualTo("new inner name");
+		assertThat(result.inner.readOnly).isEqualTo("readonly value");
+		assertThat(result.inner.hidden).isEqualTo("hidden value");
+		assertThat(result.inner).isSameAs(inner);
+	}
+
 	@SuppressWarnings("unchecked")
 	private static <T> T as(Object source, Class<T> type) {
 
@@ -715,6 +742,8 @@ static class Inner {
 
 		String name;
 		String prop;
+		@JsonProperty(access = READ_ONLY) String readOnly;
+		@JsonIgnore String hidden;
 	}
 
 	@JsonAutoDetect(fieldVisibility = Visibility.ANY)