Polishing.

Add license headers. Update Javadoc, author, and since tags. Add tests. Add toCriteriaDefinition method.

See #3790

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

@@ -498,17 +498,18 @@ public class Aggregation {
 	public static MatchOperation match(CriteriaDefinition criteria) {
 		return new MatchOperation(criteria);
 	}
-	
+
 	/**
-	 * Creates a new {@link MatchOperation}
+	 * Creates a new {@link MatchOperation} using the given {@link AggregationExpression}.
 	 *
+	 * @param expression must not be {@literal null}.
 	 * @return new instance of {@link MatchOperation}.
-	 * @since 1.10
+	 * @since 3.3
 	 */
-	public static MatchOperation match() {
-		return new MatchOperation();
+	public static MatchOperation match(AggregationExpression expression) {
+		return new MatchOperation(expression);
 	}
-	
+
 	/**
 	 * Creates a new {@link GeoNearOperation} instance from the given {@link NearQuery} and the {@code distanceField}. The
 	 * {@code distanceField} defines output field that contains the calculated distance.

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

@@ -1,9 +1,33 @@
+/*
+ * Copyright 2021 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
+ *
+ *      https://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 org.bson.Document;
+
+import org.springframework.data.mongodb.core.query.CriteriaDefinition;
 import org.springframework.util.Assert;
 
+/**
+ * Gateway to {@literal evaluation operators} such as {@literal $expr}.
+ *
+ * @author Divya Srivastava
+ * @since 3.3
+ */
 public class EvaluationOperators {
-	
+
 	/**
 	 * Take the value resulting from the given fieldReference.
 	 *
@@ -13,7 +37,7 @@ public class EvaluationOperators {
 	public static EvaluationOperatorFactory valueOf(String fieldReference) {
 		return new EvaluationOperatorFactory(fieldReference);
 	}
-	
+
 	/**
 	 * Take the value resulting from the given {@link AggregationExpression}.
 	 *
@@ -23,12 +47,12 @@ public class EvaluationOperators {
 	public static EvaluationOperatorFactory valueOf(AggregationExpression expression) {
 		return new EvaluationOperatorFactory(expression);
 	}
-	
+
 	public static class EvaluationOperatorFactory {
-		
+
 		private final String fieldReference;
 		private final AggregationExpression expression;
-		
+
 		/**
 		 * Creates new {@link EvaluationOperatorFactory} for given {@literal fieldReference}.
 		 *
@@ -41,7 +65,6 @@ public class EvaluationOperators {
 			this.expression = null;
 		}
 
-		
 		/**
 		 * Creates new {@link EvaluationOperatorFactory} for given {@link AggregationExpression}.
 		 *
@@ -53,7 +76,7 @@ public class EvaluationOperators {
 			this.fieldReference = null;
 			this.expression = expression;
 		}
-		
+
 		/**
 		 * Creates new {@link AggregationExpression} that is a valid aggregation expression.
 		 *
@@ -62,8 +85,10 @@ public class EvaluationOperators {
 		public Expr expr() {
 			return usesFieldRef() ? Expr.valueOf(fieldReference) : Expr.valueOf(expression);
 		}
-		
-		
+
+		/**
+		 * Allows the use of aggregation expressions within the query language.
+		 */
 		public static class Expr extends AbstractAggregationExpression {
 
 			private Expr(Object value) {
@@ -99,8 +124,29 @@ public class EvaluationOperators {
 				return new Expr(expression);
 			}
 
+			/**
+			 * Creates {@code $expr} as {@link CriteriaDefinition}.
+			 *
+			 * @return the {@link CriteriaDefinition} from this expression.
+			 */
+			public CriteriaDefinition toCriteriaDefinition(AggregationOperationContext context) {
+
+				Document criteriaObject = toDocument(context);
+
+				return new CriteriaDefinition() {
+					@Override
+					public Document getCriteriaObject() {
+						return criteriaObject;
+					}
+
+					@Override
+					public String getKey() {
+						return getMongoMethod();
+					}
+				};
+			}
 		}
-		
+
 		private boolean usesFieldRef() {
 			return fieldReference != null;
 		}

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

@@ -16,7 +16,7 @@
 package org.springframework.data.mongodb.core.aggregation;
 
 import org.bson.Document;
-import org.springframework.data.mongodb.core.aggregation.EvaluationOperators.EvaluationOperatorFactory.Expr;
+
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
 import org.springframework.util.Assert;
 
@@ -30,6 +30,7 @@ import org.springframework.util.Assert;
  * @author Sebastian Herold
  * @author Thomas Darimont
  * @author Oliver Gierke
+ * @author Divya Srivastava
  * @since 1.3
  * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/match/">MongoDB Aggregation Framework:
  *      $match</a>
@@ -38,15 +39,7 @@ public class MatchOperation implements AggregationOperation {
 
 	private final CriteriaDefinition criteriaDefinition;
 	private final AggregationExpression expression;
-	
-	/**
-	 * Creates a new {@link MatchOperation}
-	 */
-	public MatchOperation() {
-		this.criteriaDefinition = null;
-		this.expression = null;
-	}
-	
+
 	/**
 	 * Creates a new {@link MatchOperation} for the given {@link CriteriaDefinition}.
 	 *
@@ -55,41 +48,34 @@ public class MatchOperation implements AggregationOperation {
 	public MatchOperation(CriteriaDefinition criteriaDefinition) {
 
 		Assert.notNull(criteriaDefinition, "Criteria must not be null!");
+
 		this.criteriaDefinition = criteriaDefinition;
 		this.expression = null;
 	}
-	
-	/**
-	 * Creates a new {@link MatchOperation} for the given {@link Expression}.
-	 *
-	 * @param criteriaDefinition must not be {@literal null}.
-	 */
-	private MatchOperation(Expr expression) {
-		Assert.notNull(expression, "Expression must not be null!");
-		this.criteriaDefinition = null;
-		this.expression = expression;
-	}
-	
+
 	/**
 	 * Creates a new {@link MatchOperation} for the given {@link AggregationExpression}.
 	 *
 	 * @param expression must not be {@literal null}.
+	 * @since 3.3
 	 */
-	public MatchOperation withValueOf(AggregationExpression expression) {
+	public MatchOperation(AggregationExpression expression) {
+
 		Assert.notNull(expression, "Expression must not be null!");
-		return new MatchOperation(EvaluationOperators.valueOf(expression).expr());
+
+		this.criteriaDefinition = null;
+		this.expression = expression;
 	}
-	
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 	 */
 	@Override
 	public Document toDocument(AggregationOperationContext context) {
-		if(expression != null) {
-			return new Document(getOperator(), expression.toDocument());
-		}
-		return new Document(getOperator(), context.getMappedObject(criteriaDefinition.getCriteriaObject()));
+
+		return new Document(getOperator(),
+				context.getMappedObject(expression != null ? expression.toDocument() : criteriaDefinition.getCriteriaObject()));
 	}
 
 	/*

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

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2021 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
+ *
+ *      https://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.springframework.data.mongodb.test.util.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for {@link EvaluationOperators}.
+ *
+ * @author Mark Paluch
+ */
+class EvaluationOperatorsUnitTests {
+
+	@Test // GH-3790
+	void shouldRenderExprCorrectly() {
+
+		assertThat(EvaluationOperators.valueOf("foo").expr().toDocument(Aggregation.DEFAULT_CONTEXT))
+				.isEqualTo("{ $expr: \"$foo\" }");
+	}
+}

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

@@ -1,26 +1,23 @@
 package org.springframework.data.mongodb.core.aggregation;
 
-import static org.assertj.core.api.Assertions.*;
 
-import org.bson.Document;
+import static org.springframework.data.mongodb.test.util.Assertions.*;
+
 import org.junit.jupiter.api.Test;
 
+/**
+ * Unit tests for {@link MatchOperation}.
+ *
+ * @author Divya Srivastava
+ */
 class MatchOperationUnitTests {
-	
-	@Test // DATAMONGO - 3729
-	public void shouldRenderStdDevPopCorrectly() {
-		MatchOperation operation = Aggregation.match().withValueOf(ArithmeticOperators.valueOf("quiz").stdDevPop());
+
+	@Test // GH-3790
+	void matchShouldRenderCorrectly() {
+
+		MatchOperation operation = Aggregation.match(ArithmeticOperators.valueOf("quiz").stdDevPop());
 		assertThat(operation.toDocument(Aggregation.DEFAULT_CONTEXT)).
-			isEqualTo(Document.parse("{ $match: { \"$expr\" : { \"$stdDevPop\" : \"$quiz\" } } } "));
-		
-	}
-	
-	@Test // DATAMONGO - 3729
-	public void shouldRenderStdDevSampCorrectly() {
-		MatchOperation operation = Aggregation.match().withValueOf(ArithmeticOperators.valueOf("quiz").stdDevSamp());
-		assertThat(operation.toDocument(Aggregation.DEFAULT_CONTEXT)).
-			isEqualTo(Document.parse("{ $match: { \"$expr\" : { \"$stdDevSamp\" : \"$quiz\" } } } "));
-		
+				isEqualTo("{ $match: { \"$stdDevPop\" : \"$quiz\" } } ");
 	}
 
 }

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

@@ -27,20 +27,20 @@ import org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.Re
  *
  * @author Mark Paluch
  */
-public class ReplaceRootOperationUnitTests {
+class ReplaceRootOperationUnitTests {
 
 	@Test // DATAMONGO-1550
-	public void rejectsNullField() {
+	void rejectsNullField() {
 		assertThatIllegalArgumentException().isThrownBy(() -> new ReplaceRootOperation((Field) null));
 	}
 
 	@Test // DATAMONGO-1550
-	public void rejectsNullExpression() {
+	void rejectsNullExpression() {
 		assertThatIllegalArgumentException().isThrownBy(() -> new ReplaceRootOperation((AggregationExpression) null));
 	}
 
 	@Test // DATAMONGO-1550
-	public void shouldRenderCorrectly() {
+	void shouldRenderCorrectly() {
 
 		ReplaceRootOperation operation = ReplaceRootDocumentOperation.builder()
 				.withDocument(new Document("hello", "world"));
@@ -50,7 +50,7 @@ public class ReplaceRootOperationUnitTests {
 	}
 
 	@Test // DATAMONGO-1550
-	public void shouldRenderExpressionCorrectly() {
+	void shouldRenderExpressionCorrectly() {
 
 		ReplaceRootOperation operation = new ReplaceRootOperation(VariableOperators //
 				.mapItemsOf("array") //
@@ -64,7 +64,7 @@ public class ReplaceRootOperationUnitTests {
 	}
 
 	@Test // DATAMONGO-1550
-	public void shouldComposeDocument() {
+	void shouldComposeDocument() {
 
 		ReplaceRootOperation operation = ReplaceRootDocumentOperation.builder().withDocument() //
 				.andValue("value").as("key") //
@@ -77,7 +77,7 @@ public class ReplaceRootOperationUnitTests {
 	}
 
 	@Test // DATAMONGO-1550
-	public void shouldComposeSubDocument() {
+	void shouldComposeSubDocument() {
 
 		Document partialReplacement = new Document("key", "override").append("key2", "value2");
 
@@ -92,7 +92,7 @@ public class ReplaceRootOperationUnitTests {
 	}
 
 	@Test // DATAMONGO-1550
-	public void shouldNotExposeFields() {
+	void shouldNotExposeFields() {
 
 		ReplaceRootOperation operation = new ReplaceRootOperation(Fields.field("field"));
 

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

@@ -25,15 +25,15 @@ import org.junit.jupiter.api.Test;
  *
  * @author Christoph Strobl
  */
-public class ReplaceWithOperationUnitTests {
+class ReplaceWithOperationUnitTests {
 
 	@Test // DATAMONGO-2331
-	public void rejectsNullField() {
+	void rejectsNullField() {
 		assertThatIllegalArgumentException().isThrownBy(() -> new ReplaceWithOperation(null));
 	}
 
 	@Test // DATAMONGO-2331
-	public void shouldRenderValueCorrectly() {
+	void shouldRenderValueCorrectly() {
 
 		ReplaceWithOperation operation = ReplaceWithOperation.replaceWithValue(new Document("hello", "world"));
 		Document dbObject = operation.toDocument(Aggregation.DEFAULT_CONTEXT);
@@ -42,7 +42,7 @@ public class ReplaceWithOperationUnitTests {
 	}
 
 	@Test // DATAMONGO-2331
-	public void shouldRenderExpressionCorrectly() {
+	void shouldRenderExpressionCorrectly() {
 
 		ReplaceWithOperation operation = ReplaceWithOperation.replaceWithValueOf(VariableOperators //
 				.mapItemsOf("array") //

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

@@ -43,6 +43,9 @@ import org.springframework.data.domain.Sort.Direction;
 import org.springframework.data.geo.Point;
 import org.springframework.data.mongodb.core.DocumentTestUtils;
 import org.springframework.data.mongodb.core.Person;
+import org.springframework.data.mongodb.core.aggregation.ConditionalOperators;
+import org.springframework.data.mongodb.core.aggregation.EvaluationOperators;
+import org.springframework.data.mongodb.core.aggregation.TypeBasedAggregationOperationContext;
 import org.springframework.data.mongodb.core.geo.GeoJsonPoint;
 import org.springframework.data.mongodb.core.geo.GeoJsonPolygon;
 import org.springframework.data.mongodb.core.mapping.DBRef;
@@ -1330,6 +1333,21 @@ public class QueryMapperUnitTests {
 		assertThat(mapper.getMappedSort(query.getQueryObject(), context.getPersistentEntity(Customer.class))).isEqualTo(new org.bson.Document("address.street", "1007 Mountain Drive"));
 	}
 
+	@Test // GH-3790
+	void shouldAcceptExprAsCriteriaDefinition() {
+
+		EvaluationOperators.EvaluationOperatorFactory.Expr expr = EvaluationOperators
+				.valueOf(ConditionalOperators.ifNull("customizedField").then(true)).expr();
+
+		Query query = query(
+				expr.toCriteriaDefinition(new TypeBasedAggregationOperationContext(EmbeddedClass.class, context, mapper)));
+
+		org.bson.Document mappedQuery = mapper.getMappedObject(query.getQueryObject(),
+				context.getRequiredPersistentEntity(EmbeddedClass.class));
+
+		assertThat(mappedQuery).isEqualTo("{ $expr : { $ifNull : [\"$fancy_custom_name\", true] } }");
+	}
+
 	@Test // GH-3668
 	void mapStringIdFieldProjection() {