diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Aggregation.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Aggregation.java
index 124dd6517..efe60dcb3 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Aggregation.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Aggregation.java
@@ -424,6 +424,7 @@ public class Aggregation {
 	 *
 	 * @param groupByField must not be {@literal null} or empty.
 	 * @return
+	 * @since 1.10
 	 */
 	public static BucketOperation bucket(String groupByField) {
 		return new BucketOperation(field(groupByField));
@@ -434,6 +435,7 @@ public class Aggregation {
 	 *
 	 * @param groupByExpression must not be {@literal null}.
 	 * @return
+	 * @since 1.10
 	 */
 	public static BucketOperation bucket(AggregationExpression groupByExpression) {
 		return new BucketOperation(groupByExpression);
@@ -445,6 +447,7 @@ public class Aggregation {
 	 * @param groupByField must not be {@literal null} or empty.
 	 * @param buckets number of buckets, must be a positive integer.
 	 * @return
+	 * @since 1.10
 	 */
 	public static BucketAutoOperation bucketAuto(String groupByField, int buckets) {
 		return new BucketAutoOperation(field(groupByField), buckets);
@@ -456,6 +459,7 @@ public class Aggregation {
 	 * @param groupByExpression must not be {@literal null}.
 	 * @param buckets number of buckets, must be a positive integer.
 	 * @return
+	 * @since 1.10
 	 */
 	public static BucketAutoOperation bucketAuto(AggregationExpression groupByExpression, int buckets) {
 		return new BucketAutoOperation(groupByExpression, buckets);
@@ -465,6 +469,7 @@ public class Aggregation {
 	 * Creates a new {@link FacetOperation}.
 	 *
 	 * @return
+	 * @since 1.10
 	 */
 	public static FacetOperation facet() {
 		return FacetOperation.EMPTY;
@@ -475,6 +480,7 @@ public class Aggregation {
 	 *
 	 * @param aggregationOperations the sub-pipeline, must not be {@literal null}.
 	 * @return
+	 * @since 1.10
 	 */
 	public static FacetOperationBuilder facet(AggregationOperation... aggregationOperations) {
 		return facet().and(aggregationOperations);
diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOperationRenderer.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOperationRenderer.java
index 20dcb58a7..0cb930df1 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOperationRenderer.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOperationRenderer.java
@@ -28,7 +28,7 @@ import com.mongodb.DBObject;
 
 /**
  * Rendering support for {@link AggregationOperation} into a {@link List} of {@link com.mongodb.DBObject}.
- * 
+ *
  * @author Mark Paluch
  * @author Christoph Strobl
  * @since 1.10
@@ -40,7 +40,7 @@ class AggregationOperationRenderer {
 	/**
 	 * Render a {@link List} of {@link AggregationOperation} given {@link AggregationOperationContext} into their
 	 * {@link DBObject} representation.
-	 * 
+	 *
 	 * @param operations must not be {@literal null}.
 	 * @param context must not be {@literal null}.
 	 * @return the {@link List} of {@link DBObject}.
diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperation.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperation.java
index 9ad0d6f66..987d85916 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperation.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperation.java
@@ -23,18 +23,18 @@ import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
 
 /**
- * Encapsulates the aggregation framework {@code $bucketAuto}-operation.
- * <p>
+ * Encapsulates the aggregation framework {@code $bucketAuto}-operation. <br />
  * Bucket stage is typically used with {@link Aggregation} and {@code $facet}. Categorizes incoming documents into a
  * specific number of groups, called buckets, based on a specified expression. Bucket boundaries are automatically
- * determined in an attempt to evenly distribute the documents into the specified number of buckets.
- * <p>
- * We recommend to use the static factory method {@link Aggregation#bucketAuto(String, int)} instead of creating instances of
- * this class directly.
+ * determined in an attempt to evenly distribute the documents into the specified number of buckets. <br />
+ * We recommend to use the static factory method {@link Aggregation#bucketAuto(String, int)} instead of creating
+ * instances of this class directly.
  *
- * @see http://docs.mongodb.org/manual/reference/aggregation/bucketAuto/
+ * @see <a href=
+ *      "http://docs.mongodb.org/manual/reference/aggregation/bucketAuto/">http://docs.mongodb.org/manual/reference/aggregation/bucketAuto/</a>
  * @see BucketOperationSupport
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 1.10
  */
 public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperation, BucketAutoOperationOutputBuilder>
@@ -100,13 +100,12 @@ public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperat
 		DBObject options = new BasicDBObject();
 
 		options.put("buckets", buckets);
+		options.putAll(super.toDBObject(context));
 
 		if (granularity != null) {
 			options.put("granularity", granularity);
 		}
 
-		options.putAll(super.toDBObject(context));
-
 		return new BasicDBObject("$bucketAuto", options);
 	}
 
@@ -123,8 +122,10 @@ public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperat
 	}
 
 	/**
-	 * Configures {@literal granularity} that specifies the preferred number series to use to ensure that the calculated
-	 * boundary edges end on preferred round numbers or their powers of 10 and return a new {@link BucketAutoOperation}.
+	 * Configures {@link Granularity granularity} that specifies the preferred number series to use to ensure that the
+	 * calculated boundary edges end on preferred round numbers or their powers of 10 and return a new
+	 * {@link BucketAutoOperation}. <br />
+	 * Use either predefined {@link Granularities} or provide a own one.
 	 *
 	 * @param granularity must not be {@literal null}.
 	 * @return
@@ -133,7 +134,7 @@ public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperat
 
 		Assert.notNull(granularity, "Granularity must not be null!");
 
-		return new BucketAutoOperation(this, buckets, granularity.toMongoGranularity());
+		return new BucketAutoOperation(this, buckets, granularity.getMongoRepresentation());
 	}
 
 	/* (non-Javadoc)
@@ -196,7 +197,7 @@ public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperat
 	/**
 	 * {@link ExpressionBucketOperationBuilderSupport} implementation for {@link BucketAutoOperation} using SpEL
 	 * expression based {@link Output}.
-	 * 
+	 *
 	 * @author Mark Paluch
 	 */
 	public static class ExpressionBucketAutoOperationBuilder
@@ -227,19 +228,20 @@ public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperat
 	/**
 	 * @author Mark Paluch
 	 */
-	public static interface Granularity {
+	public interface Granularity {
 
 		/**
-		 * @return a String that represents a MongoDB granularity to be used with {@link BucketAutoOperation}.
+		 * @return a String that represents a MongoDB granularity to be used with {@link BucketAutoOperation}. Never
+		 *         {@literal null}.
 		 */
-		String toMongoGranularity();
+		String getMongoRepresentation();
 	}
 
 	/**
 	 * Supported MongoDB granularities.
 	 *
-	 * @see https://en.wikipedia.org/wiki/Preferred_number
-	 * @see https://docs.mongodb.com/manual/reference/operator/aggregation/bucketAuto/#granularity
+	 * @see <a
+	 *      href="https://docs.mongodb.com/manual/reference/operator/aggregation/bucketAuto/#granularity>https://docs.mongodb.com/manual/reference/operator/aggregation/bucketAuto/#granularity</a>
 	 * @author Mark Paluch
 	 */
 	public enum Granularities implements Granularity {
@@ -252,7 +254,7 @@ public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperat
 
 		POWERSOF2;
 
-		final String granularity;
+		private final String granularity;
 
 		Granularities() {
 			this.granularity = name();
@@ -266,7 +268,7 @@ public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperat
 		 * @see org.springframework.data.mongodb.core.aggregation.GranularitytoMongoGranularity()
 		 */
 		@Override
-		public String toMongoGranularity() {
+		public String getMongoRepresentation() {
 			return granularity;
 		}
 	}
diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperation.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperation.java
index 080ece369..4d64196bb 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperation.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperation.java
@@ -27,15 +27,15 @@ import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
 
 /**
- * Encapsulates the aggregation framework {@code $bucket}-operation.
- * <p>
+ * Encapsulates the aggregation framework {@code $bucket}-operation. <br />
+ *
  * Bucket stage is typically used with {@link Aggregation} and {@code $facet}. Categorizes incoming documents into
- * groups, called buckets, based on a specified expression and bucket boundaries.
- * <p>
+ * groups, called buckets, based on a specified expression and bucket boundaries. <br />
+ *
  * We recommend to use the static factory method {@link Aggregation#bucket(String)} instead of creating instances of
  * this class directly.
  *
- * @see http://docs.mongodb.org/manual/reference/aggregation/bucket/
+ * @see <a href="http://docs.mongodb.org/manual/reference/aggregation/bucket/">http://docs.mongodb.org/manual/reference/aggregation/bucket/</a>
  * @see BucketOperationSupport
  * @author Mark Paluch
  * @since 1.10
@@ -109,7 +109,7 @@ public class BucketOperation extends BucketOperationSupport<BucketOperation, Buc
 
 	/**
 	 * Configures a default bucket {@literal literal} and return a new {@link BucketOperation}.
-	 * 
+	 *
 	 * @param literal must not be {@literal null}.
 	 * @return
 	 */
@@ -122,13 +122,14 @@ public class BucketOperation extends BucketOperationSupport<BucketOperation, Buc
 	/**
 	 * Configures {@literal boundaries} and return a new {@link BucketOperation}. Existing {@literal boundaries} are
 	 * preserved and the new {@literal boundaries} are appended.
-	 * 
+	 *
 	 * @param boundaries must not be {@literal null}.
 	 * @return
 	 */
 	public BucketOperation withBoundaries(Object... boundaries) {
 
 		Assert.notNull(boundaries, "Boundaries must not be null!");
+		Assert.noNullElements(boundaries, "Boundaries must not contain null values!");
 
 		List<Object> newBoundaries = new ArrayList<Object>(this.boundaries.size() + boundaries.length);
 		newBoundaries.addAll(this.boundaries);
@@ -197,7 +198,7 @@ public class BucketOperation extends BucketOperationSupport<BucketOperation, Buc
 	/**
 	 * {@link ExpressionBucketOperationBuilderSupport} implementation for {@link BucketOperation} using SpEL expression
 	 * based {@link Output}.
-	 * 
+	 *
 	 * @author Mark Paluch
 	 */
 	public static class ExpressionBucketOperationBuilder
diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperationSupport.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperationSupport.java
index 05a5bdb4c..c78eddddd 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperationSupport.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperationSupport.java
@@ -31,14 +31,12 @@ import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
 
 /**
- * Base class for bucket operations that support output expressions the aggregation framework.
- * <p>
- * Bucket stages collect documents into buckets and can contribute output fields.
- * <p>
+ * Base class for bucket operations that support output expressions the aggregation framework. <br />
+ * Bucket stages collect documents into buckets and can contribute output fields. <br />
  * Implementing classes are required to provide an {@link OutputBuilder}.
  *
- * @see http://docs.mongodb.org/manual/reference/aggregation/bucket/
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 1.10
  */
 public abstract class BucketOperationSupport<T extends BucketOperationSupport<T, B>, B extends OutputBuilder<B, T>>
@@ -50,7 +48,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 	/**
 	 * Creates a new {@link BucketOperationSupport} given a {@link Field group-by field}.
-	 * 
+	 *
 	 * @param groupByField must not be {@literal null}.
 	 */
 	protected BucketOperationSupport(Field groupByField) {
@@ -60,7 +58,6 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 		this.groupByField = groupByField;
 		this.groupByExpression = null;
 		this.outputs = Outputs.EMPTY;
-
 	}
 
 	/**
@@ -79,7 +76,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 	/**
 	 * Creates a copy of {@link BucketOperationSupport}.
-	 * 
+	 *
 	 * @param operationSupport must not be {@literal null}.
 	 */
 	protected BucketOperationSupport(BucketOperationSupport<?, ?> operationSupport) {
@@ -88,7 +85,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 	/**
 	 * Creates a copy of {@link BucketOperationSupport} and applies the new {@link Outputs}.
-	 * 
+	 *
 	 * @param operationSupport must not be {@literal null}.
 	 * @param outputs must not be {@literal null}.
 	 */
@@ -105,7 +102,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 	/**
 	 * Creates a new {@link ExpressionBucketOperationBuilderSupport} given a SpEL {@literal expression} and optional
 	 * {@literal params} to add an output field to the resulting bucket documents.
-	 * 
+	 *
 	 * @param expression the SpEL expression, must not be {@literal null} or empty.
 	 * @param params must not be {@literal null}
 	 * @return
@@ -186,7 +183,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 	/**
 	 * Builder for SpEL expression-based {@link Output}.
-	 * 
+	 *
 	 * @author Mark Paluch
 	 */
 	public abstract static class ExpressionBucketOperationBuilderSupport<B extends OutputBuilder<B, T>, T extends BucketOperationSupport<T, B>>
@@ -232,11 +229,9 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 		}
 
 		/**
-		 * Generates a builder for a {@code $sum}-expression.
-		 * <p>
+		 * Generates a builder for a {@code $sum}-expression. <br />
 		 * Count expressions are emulated via {@code $sum: 1}.
-		 * <p>
-		 * 
+		 *
 		 * @return
 		 */
 		public B count() {
@@ -245,7 +240,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Generates a builder for a {@code $sum}-expression for the current value.
-		 * 
+		 *
 		 * @return
 		 */
 		public B sum() {
@@ -259,12 +254,12 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 		 * @return
 		 */
 		public B sum(Number value) {
-			return apply(new OperationOutput(Accumulators.SUM.toString(), Collections.singleton(value)));
+			return apply(new OperationOutput(Accumulators.SUM.getMongoOperator(), Collections.singleton(value)));
 		}
 
 		/**
 		 * Generates a builder for an {@code $last}-expression for the current value..
-		 * 
+		 *
 		 * @return
 		 */
 		public B last() {
@@ -273,7 +268,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Generates a builder for a {@code $first}-expression the current value.
-		 * 
+		 *
 		 * @return
 		 */
 		public B first() {
@@ -282,7 +277,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Generates a builder for an {@code $avg}-expression for the current value.
-		 * 
+		 *
 		 * @param reference
 		 * @return
 		 */
@@ -292,7 +287,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Generates a builder for an {@code $min}-expression for the current value.
-		 * 
+		 *
 		 * @return
 		 */
 		public B min() {
@@ -301,7 +296,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Generates a builder for an {@code $max}-expression for the current value.
-		 * 
+		 *
 		 * @return
 		 */
 		public B max() {
@@ -346,14 +341,14 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Apply an {@link OperationOutput} to this output.
-		 * 
+		 *
 		 * @param operationOutput must not be {@literal null}.
 		 * @return
 		 */
 		protected abstract B apply(OperationOutput operationOutput);
 
 		private B apply(Accumulators operation) {
-			return this.apply(operation.toString());
+			return this.apply(operation.getMongoOperator());
 		}
 
 		/**
@@ -388,18 +383,14 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 			this.mongoOperator = mongoOperator;
 		}
 
-		/* (non-Javadoc)
-		 * @see java.lang.Enum#toString()
-		 */
-		@Override
-		public String toString() {
+		public String getMongoOperator() {
 			return mongoOperator;
 		}
 	}
 
 	/**
 	 * Encapsulates {@link Output}s.
-	 * 
+	 *
 	 * @author Mark Paluch
 	 */
 	protected static class Outputs implements AggregationExpression {
@@ -417,7 +408,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Creates new {@link Outputs} containing all given {@link Output}s.
-		 * 
+		 *
 		 * @param current
 		 * @param output
 		 */
@@ -449,7 +440,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 		/**
 		 * Create a new {@link Outputs} that contains the new {@link Output}.
-		 * 
+		 *
 		 * @param output must not be {@literal null}.
 		 * @return the new {@link Outputs} that contains the new {@link Output}
 		 */
@@ -484,11 +475,10 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 	}
 
 	/**
-	 * Encapsulates an output field in a bucket aggregation stage.
-	 * <p>
+	 * Encapsulates an output field in a bucket aggregation stage. <br />
 	 * Output fields can be either top-level fields that define a valid field name or nested output fields using
 	 * operators.
-	 * 
+	 *
 	 * @author Mark Paluch
 	 */
 	protected abstract static class Output implements AggregationExpression {
@@ -514,17 +504,10 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 		protected ExposedField getExposedField() {
 			return field;
 		}
-
-		/* (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
-		 */
-		@Override
-		public abstract DBObject toDbObject(AggregationOperationContext context);
 	}
 
 	/**
-	 * Output field that uses a Mongo operation (expression object) to generate an output field value.
-	 * <p>
+	 * Output field that uses a Mongo operation (expression object) to generate an output field value. <br />
 	 * {@link OperationOutput} is used either with a regular field name or an operation keyword (e.g.
 	 * {@literal $sum, $count}).
 	 *
@@ -624,7 +607,6 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 
 					// We have to make sure that we use the arguments from the "previous" OperationOutput that we replace
 					// with this new instance.
-
 					return OperationOutput.this.getOperationArguments(context);
 				}
 			};
@@ -634,7 +616,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 	/**
 	 * A {@link Output} based on a SpEL expression.
 	 */
-	static class SpelExpressionOutput extends Output {
+	private static class SpelExpressionOutput extends Output {
 
 		private static final SpelExpressionTransformer TRANSFORMER = new SpelExpressionTransformer();
 
@@ -663,11 +645,7 @@ public abstract class BucketOperationSupport<T extends BucketOperationSupport<T,
 		 */
 		@Override
 		public DBObject toDbObject(AggregationOperationContext context) {
-			return (DBObject) toMongoExpression(context, expression, params);
-		}
-
-		protected static Object toMongoExpression(AggregationOperationContext context, String expression, Object[] params) {
-			return TRANSFORMER.transform(expression, context, params);
+			return (DBObject) TRANSFORMER.transform(expression, context, params);
 		}
 	}
 
diff --git a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/FacetOperation.java b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/FacetOperation.java
index 9082acedf..bb1d6b8fe 100644
--- a/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/FacetOperation.java
+++ b/spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/FacetOperation.java
@@ -28,22 +28,20 @@ import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
 
 /**
- * Encapsulates the aggregation framework {@code $facet}-operation.
- * <p>
+ * Encapsulates the aggregation framework {@code $facet}-operation. <br />
  * Facet of {@link AggregationOperation}s to be used in an {@link Aggregation}. Processes multiple
  * {@link AggregationOperation} pipelines within a single stage on the same set of input documents. Each sub-pipeline
  * has its own field in the output document where its results are stored as an array of documents.
  * {@link FacetOperation} enables various aggregations on the same set of input documents, without needing to retrieve
- * the input documents multiple times.
- * <p>
+ * the input documents multiple times. <br />
  * As of MongoDB 3.4, {@link FacetOperation} cannot be used with nested pipelines containing {@link GeoNearOperation},
- * {@link OutOperation} and {@link FacetOperation}.
- * <p>
+ * {@link OutOperation} and {@link FacetOperation}. <br />
  * We recommend to use the static factory method {@link Aggregation#facet()} instead of creating instances of this class
  * directly.
  *
  * @see http://docs.mongodb.org/manual/reference/aggregation/facet/
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 1.10
  */
 public class FacetOperation implements FieldsExposingAggregationOperation {
@@ -67,11 +65,10 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Creates a new {@link FacetOperationBuilder} to append a new facet using {@literal operations}.
-	 * <p>
+	 * Creates a new {@link FacetOperationBuilder} to append a new facet using {@literal operations}. <br />
 	 * {@link FacetOperationBuilder} takes a pipeline of {@link AggregationOperation} to categorize documents into a
 	 * single facet.
-	 * 
+	 *
 	 * @param operations must not be {@literal null} or empty.
 	 * @return
 	 */
@@ -118,7 +115,7 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Creates a new {@link FacetOperation} that contains the configured pipeline of {@link AggregationOperation}
 		 * exposed as {@literal fieldName} in the resulting facet document.
-		 * 
+		 *
 		 * @param fieldName must not be {@literal null} or empty.
 		 * @return
 		 */
@@ -132,7 +129,7 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Encapsulates multiple {@link Facet}s
-	 * 
+	 *
 	 * @author Mark Paluch
 	 */
 	private static class Facets {
@@ -143,7 +140,7 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Creates a new {@link Facets} given {@link List} of {@link Facet}.
-		 * 
+		 *
 		 * @param facets
 		 */
 		private Facets(List<Facet> facets) {
@@ -153,7 +150,7 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * @return the {@link ExposedFields} derived from {@link Output}.
 		 */
-		protected ExposedFields asExposedFields() {
+		ExposedFields asExposedFields() {
 
 			ExposedFields fields = ExposedFields.from();
 
@@ -164,7 +161,7 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 			return fields;
 		}
 
-		protected DBObject toDBObject(AggregationOperationContext context) {
+		DBObject toDBObject(AggregationOperationContext context) {
 
 			DBObject dbObject = new BasicDBObject(facets.size());
 
@@ -177,12 +174,12 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Adds a facet to this {@link Facets}.
-		 * 
+		 *
 		 * @param fieldName must not be {@literal null}.
 		 * @param operations must not be {@literal null}.
 		 * @return the new {@link Facets}.
 		 */
-		public Facets and(String fieldName, List<AggregationOperation> operations) {
+		Facets and(String fieldName, List<AggregationOperation> operations) {
 
 			Assert.hasText(fieldName, "FieldName must not be null or empty!");
 			Assert.notNull(operations, "AggregationOperations must not be null!");
@@ -197,7 +194,7 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * A single facet with a {@link ExposedField} and its {@link AggregationOperation} pipeline.
-	 * 
+	 *
 	 * @author Mark Paluch
 	 */
 	private static class Facet {
@@ -207,11 +204,11 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Creates a new {@link Facet} given {@link ExposedField} and {@link AggregationOperation} pipeline.
-		 * 
+		 *
 		 * @param exposedField must not be {@literal null}.
 		 * @param operations must not be {@literal null}.
 		 */
-		protected Facet(ExposedField exposedField, List<AggregationOperation> operations) {
+		Facet(ExposedField exposedField, List<AggregationOperation> operations) {
 
 			Assert.notNull(exposedField, "ExposedField must not be null!");
 			Assert.notNull(operations, "AggregationOperations must not be null!");
@@ -220,11 +217,11 @@ public class FacetOperation implements FieldsExposingAggregationOperation {
 			this.operations = operations;
 		}
 
-		protected ExposedField getExposedField() {
+		ExposedField getExposedField() {
 			return exposedField;
 		}
 
-		protected List<DBObject> toDBObjects(AggregationOperationContext context) {
+		List<DBObject> toDBObjects(AggregationOperationContext context) {
 			return AggregationOperationRenderer.toDBObject(operations, context);
 		}
 	}
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperationUnitTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperationUnitTests.java
index 77388af89..19459dc09 100644
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperationUnitTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperationUnitTests.java
@@ -28,7 +28,7 @@ import com.mongodb.util.JSON;
 
 /**
  * Unit tests for {@link BucketAutoOperation}.
- * 
+ *
  * @author Mark Paluch
  */
 public class BucketAutoOperationUnitTests {
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketOperationUnitTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketOperationUnitTests.java
index 5915c73b5..c978f37c1 100644
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketOperationUnitTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/BucketOperationUnitTests.java
@@ -29,7 +29,7 @@ import com.mongodb.util.JSON;
 
 /**
  * Unit tests for {@link BucketOperation}.
- * 
+ *
  * @author Mark Paluch
  */
 public class BucketOperationUnitTests {
diff --git a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/FacetOperationUnitTests.java b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/FacetOperationUnitTests.java
index ee40128d5..228102b7c 100644
--- a/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/FacetOperationUnitTests.java
+++ b/spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/aggregation/FacetOperationUnitTests.java
@@ -27,7 +27,7 @@ import com.mongodb.util.JSON;
 
 /**
  * Unit tests for {@link FacetOperation}.
- * 
+ *
  * @author Mark Paluch
  * @soundtrack Stanley Foort - You Make Me Believe In Magic (Extended Mix)
  */