DATAMONGO-1734 - Add exists() and count() to fluent API.

Original pull request: #479.

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

@@ -115,6 +115,20 @@ public interface ExecutableFindOperation {
 		 *         Never {@literal null}.
 		 */
 		CloseableIterator<T> stream();
+
+		/**
+		 * Get the number of matching elements.
+		 *
+		 * @return total number of matching elements.
+		 */
+		long count();
+
+		/**
+		 * Check for the presence of matching elements.
+		 *
+		 * @return {@literal true} if at least one matching element exists.
+		 */
+		boolean exists();
 	}
 
 	/**

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

@@ -41,6 +41,8 @@ import com.mongodb.client.FindIterable;
  */
 class ExecutableFindOperationSupport implements ExecutableFindOperation {
 
+	private static final Query ALL_QUERY = new BasicQuery(new Document());
+
 	private final MongoTemplate template;
 
 	/**
@@ -61,7 +63,7 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 
 		Assert.notNull(domainType, "DomainType must not be null!");
 
-		return new FindOperationSupport<>(template, domainType, domainType, null, null);
+		return new FindOperationSupport<>(template, domainType, domainType, null, ALL_QUERY);
 	}
 
 	/**
@@ -142,10 +144,20 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 			return () -> template.geoNear(nearQuery, domainType, getCollectionName(), returnType);
 		}
 
+		@Override
+		public long count() {
+			return template.count(query, domainType, getCollectionName());
+		}
+
+		@Override
+		public boolean exists() {
+			return template.exists(query, domainType, getCollectionName());
+		}
+
 		private List<T> doFind(CursorPreparer preparer) {
 
-			Document queryObject = query != null ? query.getQueryObject() : new Document();
+			Document queryObject = query.getQueryObject();
-			Document fieldsObject = query != null ? query.getFieldsObject() : new Document();
+			Document fieldsObject = query.getFieldsObject();
 
 			return template.doFind(getCollectionName(), queryObject, fieldsObject, domainType, returnType,
 					getCursorPreparer(query, preparer));
@@ -153,8 +165,7 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 
 		private CloseableIterator<T> doStream() {
 
-			return template.doStream(query != null ? query : new BasicQuery(new Document()), domainType, getCollectionName(),
+			return template.doStream(query, domainType, getCollectionName(), returnType);
-					returnType);
 		}
 
 		private CursorPreparer getCursorPreparer(Query query, CursorPreparer preparer) {

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

@@ -31,6 +31,7 @@ import org.springframework.data.geo.Point;
 import org.springframework.data.mongodb.core.index.GeoSpatialIndexType;
 import org.springframework.data.mongodb.core.index.GeospatialIndex;
 import org.springframework.data.mongodb.core.mapping.Field;
+import org.springframework.data.mongodb.core.query.BasicQuery;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.util.CloseableIterator;
 
@@ -242,6 +243,43 @@ public class ExecutableFindOperationSupportTests {
 		assertThat(template.query(Person.class).first()).isNotEmpty();
 	}
 
+	@Test // DATAMONGO-1734
+	public void countShouldReturnNrOfElementsInCollectionWhenNoQueryPresent() {
+		assertThat(template.query(Person.class).count()).isEqualTo(2);
+	}
+
+	@Test // DATAMONGO-1734
+	public void countShouldReturnNrOfElementsMatchingQuery() {
+
+		assertThat(template.query(Person.class).matching(query(where("firstname").is(luke.getFirstname()))).count())
+				.isEqualTo(1);
+	}
+
+	@Test // DATAMONGO-1734
+	public void existsShouldReturnTrueIfAtLeastOneElementExistsInCollection() {
+		assertThat(template.query(Person.class).exists()).isTrue();
+	}
+
+	@Test // DATAMONGO-1734
+	public void existsShouldReturnFalseIfNoElementExistsInCollection() {
+
+		template.remove(new BasicQuery("{}"), STAR_WARS);
+
+		assertThat(template.query(Person.class).exists()).isFalse();
+	}
+
+	@Test // DATAMONGO-1734
+	public void existsShouldReturnTrueIfAtLeastOneElementMatchesQuery() {
+
+		assertThat(template.query(Person.class).matching(query(where("firstname").is(luke.getFirstname()))).exists())
+				.isTrue();
+	}
+
+	@Test // DATAMONGO-1734
+	public void existsShouldReturnFalseWhenNoElementMatchesQuery() {
+		assertThat(template.query(Person.class).matching(query(where("firstname").is("spock"))).exists()).isFalse();
+	}
+
 	@Data
 	@org.springframework.data.mongodb.core.mapping.Document(collection = STAR_WARS)
 	static class Person {