Fix Criteria chaining for Criteria.alike().

This commit fixes an issue where an Example probe would not be added to the criteria chain.

Closes #3544
Original pull request: #3549.

Author: christophstrobl

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/query/Criteria.java

@@ -620,8 +620,15 @@ public Criteria elemMatch(Criteria criteria) {
 	 */
 	public Criteria alike(Example<?> sample) {
 
-		criteria.put("$example", sample);
-		return this;
+		if (StringUtils.hasText(this.getKey())) {
+
+			criteria.put("$example", sample);
+			return this;
+		}
+
+		Criteria exampleCriteria = new Criteria();
+		exampleCriteria.criteria.put("$example", sample);
+		return registerCriteriaChainElement(exampleCriteria);
 	}
 
 	/**

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

@@ -139,16 +139,14 @@ public void findByExampleShouldReturnEverythingWhenSampleIsEmpty() {
 		assertThat(result).containsExactlyInAnyOrder(p1, p2, p3);
 	}
 
-	@Test // DATAMONGO-1245
+	@Test // DATAMONGO-1245, GH-3544
 	public void findByExampleWithCriteria() {
 
 		Person sample = new Person();
 		sample.lastname = "stark";
 
-		Query query = new Query(new Criteria().alike(Example.of(sample)).and("firstname").regex("^ary*"));
-
-		List<Person> result = operations.find(query, Person.class);
-		assertThat(result).hasSize(1);
+		Query query = new Query(new Criteria().alike(Example.of(sample)).and("firstname").regex(".*n.*"));
+		assertThat(operations.find(query, Person.class)).containsExactly(p1);
 	}
 
 	@Test // DATAMONGO-1459

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/QueryMapperUnitTests.java

@@ -771,6 +771,19 @@ void exampleShouldBeMappedCorrectlyWhenContainingLegacyPoint() {
 		assertThat(document).containsEntry("legacyPoint.y", 20D);
 	}
 
+	@Test // GH-3544
+	void exampleWithCombinedCriteriaShouldBeMappedCorrectly() {
+
+		Foo probe = new Foo();
+		probe.embedded = new EmbeddedClass();
+		probe.embedded.id = "conflux";
+
+		Query query = query(byExample(probe).and("listOfItems").exists(true));
+		org.bson.Document document = mapper.getMappedObject(query.getQueryObject(), context.getPersistentEntity(Foo.class));
+
+		assertThat(document).containsEntry("embedded\\._id", "conflux").containsEntry("my_items", new org.bson.Document("$exists", true));
+	}
+
 	@Test // DATAMONGO-1988
 	void mapsStringObjectIdRepresentationToObjectIdWhenReferencingIdProperty() {