Add shortcut for date aggregation operators working with timezone.

See: #3713
Original pull request: #3748.

Author: christophstrobl

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/DateOperators.java

@@ -46,6 +46,19 @@ public static DateOperatorFactory dateOf(String fieldReference) {
 		return new DateOperatorFactory(fieldReference);
 	}
 
+	/**
+	 * Take the date referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return new instance of {@link DateOperatorFactory}.
+	 * @since 3.3
+	 */
+	public static DateOperatorFactory zonedDateOf(String fieldReference, Timezone timezone) {
+
+		Assert.notNull(fieldReference, "FieldReference must not be null!");
+		return new DateOperatorFactory(fieldReference).withTimezone(timezone);
+	}
+
 	/**
 	 * Take the date resulting from the given {@link AggregationExpression}.
 	 *
@@ -58,6 +71,19 @@ public static DateOperatorFactory dateOf(AggregationExpression expression) {
 		return new DateOperatorFactory(expression);
 	}
 
+	/**
+	 * Take the date resulting from the given {@link AggregationExpression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return new instance of {@link DateOperatorFactory}.
+	 * @since 3.3
+	 */
+	public static DateOperatorFactory zonedDateOf(AggregationExpression expression, Timezone timezone) {
+
+		Assert.notNull(expression, "Expression must not be null!");
+		return new DateOperatorFactory(expression).withTimezone(timezone);
+	}
+
 	/**
 	 * Take the given value as date.
 	 * <p/>

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/DateOperatorsUnitTests.java

@@ -35,8 +35,8 @@ void rendersDateAdd() {
 
 	@Test // GH-3713
 	void rendersDateAddWithTimezone() {
-		
-		assertThat(DateOperators.dateOf("purchaseDate").withTimezone(Timezone.valueOf("America/Chicago")).add(3, "day")
+
+		assertThat(DateOperators.zonedDateOf("purchaseDate", Timezone.valueOf("America/Chicago")).add(3, "day")
 				.toDocument(Aggregation.DEFAULT_CONTEXT)).isEqualTo(Document.parse(
 						"{ $dateAdd: { startDate: \"$purchaseDate\", unit: \"day\", amount: 3, timezone : \"America/Chicago\" } }"));
 	}
@@ -53,7 +53,7 @@ void rendersDateDiff() {
 	@Test // GH-3713
 	void rendersDateDiffWithTimezone() {
 
-		assertThat(DateOperators.dateOf("purchaseDate").withTimezone(Timezone.valueOf("America/Chicago"))
+		assertThat(DateOperators.zonedDateOf("purchaseDate", Timezone.valueOf("America/Chicago"))
 				.diffValueOf("delivered", "day").toDocument(Aggregation.DEFAULT_CONTEXT)).isEqualTo(Document.parse(
 						"{ $dateDiff: { startDate: \"$purchaseDate\", endDate: \"$delivered\", unit: \"day\", timezone : \"America/Chicago\" } }"));
 	}