DATAMONGO-2052 - Add support for $arrayToObject and $objectToArray aggregation operators.

Original pull request: #603.

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

@@ -267,6 +267,19 @@ public class ArrayOperators {
 			return (usesFieldRef() ? In.arrayOf(fieldReference) : In.arrayOf(expression)).containsValue(value);
 		}
 
+		/**
+		 * Creates new {@link AggregationExpression} that converts the associated expression into an object.
+		 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+		 *
+		 * @return new instance of {@link ArrayToObject}.
+		 * @since 2.1
+		 */
+		public ArrayToObject toObject() {
+
+			return usesFieldRef() ? ArrayToObject.arrayValueOfToObject(fieldReference)
+					: ArrayToObject.arrayValueOfToObject(expression);
+		}
+
 		/**
 		 * @author Christoph Strobl
 		 */
@@ -1497,4 +1510,59 @@ public class ArrayOperators {
 			In containsValue(Object value);
 		}
 	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $arrayToObject} that transforms an array into a single document. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/arrayToObject/">https://docs.mongodb.com/manual/reference/operator/aggregation/arrayToObject/</a>
+	 * @since 2.1
+	 */
+	public static class ArrayToObject extends AbstractAggregationExpression {
+
+		private ArrayToObject(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Converts the given array (e.g. an array of two-element arrays, a field reference to an array,...) to an object.
+		 *
+		 * @param array must not be {@literal null}.
+		 * @return new instance of {@link ArrayToObject}.
+		 */
+		public static ArrayToObject arrayToObject(Object array) {
+			return new ArrayToObject(array);
+		}
+
+		/**
+		 * Converts the array pointed to by the given {@link Field field reference} to an object.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link ArrayToObject}.
+		 */
+		public static ArrayToObject arrayValueOfToObject(String fieldReference) {
+			return new ArrayToObject(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Converts the result array of the given {@link AggregationExpression expression} to an object.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link ArrayToObject}.
+		 */
+		public static ArrayToObject arrayValueOfToObject(AggregationExpression expression) {
+			return new ArrayToObject(expression);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#getMongoMethod()
+		 */
+		@Override
+		protected String getMongoMethod() {
+			return "$arrayToObject";
+		}
+	}
 }

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

@@ -113,6 +113,17 @@ public class ObjectOperators {
 		public MergeObjects mergeWithValuesOf(AggregationExpression... expression) {
 			return merge().mergeWithValuesOf(expression);
 		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the associated value and converts it to an
+		 * array of {@link Document documents} that contain two fields {@literal k} and {@literal v} each. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+		 * 
+		 * @since 2.1
+		 */
+		public ObjectToArray toArray() {
+			return ObjectToArray.toArray(value);
+		}
 	}
 
 	/**
@@ -226,4 +237,62 @@ public class ObjectOperators {
 			return "$mergeObjects";
 		}
 	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $objectToArray} that converts a document to an array of {@link Document
+	 * documents} that each contains two fields {@literal k} and {@literal v}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/objectToArray/">https://docs.mongodb.com/manual/reference/operator/aggregation/objectToArray/</a>
+	 * @since 2.1
+	 */
+	public static class ObjectToArray extends AbstractAggregationExpression {
+
+		private ObjectToArray(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the value pointed to by given {@link Field
+		 * fieldReference} and converts it to an array.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link ObjectToArray}.
+		 */
+		public static ObjectToArray valueOfToArray(String fieldReference) {
+			return toArray(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the result value of the given
+		 * {@link AggregationExpression expression} and converts it to an array.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link ObjectToArray}.
+		 */
+		public static ObjectToArray valueOfToArray(AggregationExpression expression) {
+			return toArray(expression);
+		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the given value and converts it to an array.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ObjectToArray}.
+		 */
+		public static ObjectToArray toArray(Object value) {
+			return new ObjectToArray(value);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#getMongoMethod()
+		 */
+		@Override
+		protected String getMongoMethod() {
+			return "$objectToArray";
+		}
+	}
 }

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

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.bson.Document;
+import org.junit.Test;
+import org.springframework.data.mongodb.core.aggregation.ArrayOperators.ArrayToObject;
+
+/**
+ * Unit tests for {@link ArrayOperators}
+ * 
+ * @author Christoph Strobl
+ * @currentRead Royal Assassin - Robin Hobb
+ */
+public class ArrayOperatorsUnitTests {
+
+	static final String EXPRESSION_STRING = "{ \"$stablemaster\" : \"burrich\" }";
+	static final Document EXPRESSION_DOC = Document.parse(EXPRESSION_STRING);
+	static final AggregationExpression EXPRESSION = context -> EXPRESSION_DOC;
+
+	@Test // DATAMONGO-2052
+	public void toArrayWithFieldReference() {
+
+		assertThat(ArrayOperators.arrayOf("regal").toObject().toDocument(Aggregation.DEFAULT_CONTEXT))
+				.isEqualTo(Document.parse("{ $arrayToObject: \"$regal\" } "));
+	}
+
+	@Test // DATAMONGO-2052
+	public void toArrayWithExpression() {
+
+		assertThat(ArrayOperators.arrayOf(EXPRESSION).toObject().toDocument(Aggregation.DEFAULT_CONTEXT))
+				.isEqualTo(Document.parse("{ $arrayToObject: " + EXPRESSION_STRING + "} "));
+	}
+
+	@Test // DATAMONGO-2052
+	public void toArrayWithArgumentList() {
+
+		List<List<String>> source = new ArrayList<>();
+		source.add(Arrays.asList("king", "shrewd"));
+		source.add(Arrays.asList("prince", "verity"));
+
+		assertThat(ArrayToObject.arrayToObject(source).toDocument(Aggregation.DEFAULT_CONTEXT))
+				.isEqualTo(Document.parse("{ $arrayToObject: [ [ \"king\", \"shrewd\"], [ \"prince\", \"verity\" ] ] } "));
+	}
+}

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

@@ -90,4 +90,18 @@ public class ObjectOperatorsUnitTests {
 								"{ $mergeObjects: [ \"$kettricken\", " + EXPRESSION_STRING + ", { \"fitz\" : \"chivalry\" } ] } "));
 	}
 
+	@Test // DATAMONGO-2052
+	public void toArrayWithFieldReference() {
+
+		assertThat(ObjectOperators.valueOf("verity").toArray().toDocument(Aggregation.DEFAULT_CONTEXT))
+				.isEqualTo(Document.parse("{ $objectToArray : \"$verity\" }"));
+	}
+
+	@Test // DATAMONGO-2052
+	public void toArrayWithExpression() {
+
+		assertThat(ObjectOperators.valueOf(EXPRESSION).toArray().toDocument(Aggregation.DEFAULT_CONTEXT))
+				.isEqualTo(Document.parse("{ $objectToArray : " + EXPRESSION_STRING + " }"));
+	}
+
 }

src/main/asciidoc/reference/mongodb.adoc

@@ -2128,7 +2128,7 @@ At the time of this writing, we provide support for the following Aggregation Op
 | `eq` (*via: `is`), `gt`, `gte`, `lt`, `lte`, `ne`
 
 | Array Aggregation Operators
-| `arrayElementAt`, `concatArrays`, `filter`, `in`, `indexOfArray`, `isArray`, `range`, `reverseArray`, `reduce`, `size`, `slice`, `zip`
+| `arrayElementAt`, `arrayToObject`, `concatArrays`, `filter`, `in`, `indexOfArray`, `isArray`, `range`, `reverseArray`, `reduce`, `size`, `slice`, `zip`
 
 | Literal Operators
 | `literal`
@@ -2149,7 +2149,7 @@ At the time of this writing, we provide support for the following Aggregation Op
 | `convert`, `toBool`, `toDate`, `toDecimal`, `toDouble`, `toInt`, `toLong`, `toObjectId`, `toString`
 
 | Object Aggregation Operators
-| `mergeObjects`
+| `objectToArray`, `mergeObjects`
 |===
 
 * The operation is mapped or added by Spring Data MongoDB.