DATAES-978 - Accept DateFormat.none for a date property to enable cus…

src/main/asciidoc/reference/elasticsearch-object-mapping.adoc

@@ -58,13 +58,14 @@ Constructor arguments are mapped by name to the key values in the retrieved Docu
 ** `name`: The name of the field as it will be represented in the Elasticsearch document, if not set, the Java field name is used.
 ** `type`: the field type, can be one of _Text, Keyword, Long, Integer, Short, Byte, Double, Float, Half_Float, Scaled_Float, Date, Date_Nanos, Boolean, Binary, Integer_Range, Float_Range, Long_Range, Double_Range, Date_Range, Ip_Range, Object, Nested, Ip, TokenCount, Percolator, Flattened, Search_As_You_Type_.
 See https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-types.html[Elasticsearch Mapping Types]
-** `format` and `pattern` definitions for the _Date_ type. `format` must be defined for date types.
+** `format` and `pattern` definitions for the _Date_ type.
 ** `store`: Flag whether the original field value should be store in Elasticsearch, default value is _false_.
 ** `analyzer`, `searchAnalyzer`, `normalizer` for specifying custom analyzers and normalizer.
 * `@GeoPoint`: marks a field as _geo_point_ datatype.
 Can be omitted if the field is an instance of the `GeoPoint` class.
 
-NOTE: Properties that derive from `TemporalAccessor` must either have a `@Field` annotation of type `FieldType.Date` or a custom converter must be registered for this type. +
+NOTE: Properties that derive from `TemporalAccessor` or are of type `java.util.Date` must either have a `@Field` annotation of type `FieldType.Date` and a
+format different from `DateFormat.none` or a custom converter must be registered for this type. +
 If you are using a custom date format, you need to use _uuuu_ for the year instead of _yyyy_.
 This is due to a https://www.elastic.co/guide/en/elasticsearch/reference/current/migrate-to-java-time.html#java-time-migration-incompatible-date-formats[change in Elasticsearch 7].
 

src/main/java/org/springframework/data/elasticsearch/core/mapping/SimpleElasticsearchPersistentProperty.java

@@ -163,10 +163,13 @@ private void initDateConverter() {
 				&& (isTemporalAccessor || isDate)) {
 			DateFormat dateFormat = field.format();
 
+			String property = getOwner().getType().getSimpleName() + "." + getName();
+
 			if (dateFormat == DateFormat.none) {
-				throw new MappingException(
-						String.format("Property %s is annotated with FieldType.%s but has no DateFormat defined",
-								getOwner().getType().getSimpleName() + "." + getName(), field.type().name()));
+				LOGGER.warn(
+						String.format("No DateFormat defined for property %s. Make sure you have a Converter registered for %s",
+								property, actualType.getSimpleName()));
+				return;
 			}
 
 			ElasticsearchDateConverter converter;
@@ -177,7 +180,7 @@ private void initDateConverter() {
 				if (!StringUtils.hasLength(pattern)) {
 					throw new MappingException(
 							String.format("Property %s is annotated with FieldType.%s and a custom format but has no pattern defined",
-									getOwner().getType().getSimpleName() + "." + getName(), field.type().name()));
+									property, field.type().name()));
 				}
 
 				converter = ElasticsearchDateConverter.of(pattern);

src/test/java/org/springframework/data/elasticsearch/core/mapping/SimpleElasticsearchPersistentPropertyUnitTests.java

@@ -192,20 +192,6 @@ void seqNoPrimaryTermPropertyShouldNotBeReadable() {
 		assertThat(seqNoProperty.isReadable()).isFalse();
 	}
 
-	@Test // DATAES-828
-	void shouldRequireFormatForDateField() {
-		assertThatExceptionOfType(MappingException.class) //
-				.isThrownBy(() -> context.getRequiredPersistentEntity(DateFieldWithNoFormat.class)) //
-				.withMessageContaining("date");
-	}
-
-	@Test // DATAES-828
-	void shouldRequireFormatForDateNanosField() {
-		assertThatExceptionOfType(MappingException.class) //
-				.isThrownBy(() -> context.getRequiredPersistentEntity(DateNanosFieldWithNoFormat.class)) //
-				.withMessageContaining("date");
-	}
-
 	@Test // DATAES-924
 	@DisplayName("should require pattern for custom date format")
 	void shouldRequirePatternForCustomDateFormat() {