DATAMONGO-2200 - Derive fields for aggregation $project stage from a given type.

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>2.2.0.BUILD-SNAPSHOT</version>
+	<version>2.2.0.DATAMONGO-2200-SNAPSHOT</version>
 	<packaging>pom</packaging>
 
 	<name>Spring Data MongoDB</name>

spring-data-mongodb-benchmarks/pom.xml

@@ -7,7 +7,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.2.0.BUILD-SNAPSHOT</version>
+		<version>2.2.0.DATAMONGO-2200-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb-distribution/pom.xml

@@ -14,7 +14,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.2.0.BUILD-SNAPSHOT</version>
+		<version>2.2.0.DATAMONGO-2200-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/pom.xml

@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.2.0.BUILD-SNAPSHOT</version>
+		<version>2.2.0.DATAMONGO-2200-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

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

@@ -244,6 +244,19 @@ public static ProjectionOperation project(Fields fields) {
 		return new ProjectionOperation(fields);
 	}
 
+	/**
+	 * Creates a new {@link ProjectionOperation} including all top level fields of the given given {@link Class}.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return new instance of {@link ProjectionOperation}.
+	 * @since 2.2
+	 */
+	public static ProjectionOperation project(Class<?> type) {
+
+		Assert.notNull(type, "Type must not be null!");
+		return new ProjectionOperation(type);
+	}
+
 	/**
 	 * Factory method to create a new {@link UnwindOperation} for the field with the given name.
 	 *

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

@@ -15,9 +15,18 @@
  */
 package org.springframework.data.mongodb.core.aggregation;
 
+import java.beans.PropertyDescriptor;
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
 import org.bson.Document;
+import org.springframework.beans.BeanUtils;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.ReflectionUtils;
 
 /**
  * The context for an {@link AggregationOperation}.
@@ -66,4 +75,32 @@ default Document getMappedObject(Document document) {
 	 * @return
 	 */
 	FieldReference getReference(String name);
+
+	/**
+	 * Returns the {@link Fields} exposed by the type. May be a {@literal class} or an {@literal interface}.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 2.2
+	 */
+	default Fields getFields(Class<?> type) {
+
+		Assert.notNull(type, "Type must not be null!");
+
+		List<String> fields = Arrays.stream(BeanUtils.getPropertyDescriptors(type)) //
+				.filter(it -> { // object and default methods
+					Method method = it.getReadMethod();
+					if (method == null) {
+						return false;
+					}
+					if (ReflectionUtils.isObjectMethod(method)) {
+						return false;
+					}
+					return !method.isDefault();
+				}) //
+				.map(PropertyDescriptor::getName) //
+				.collect(Collectors.toList());
+
+		return Fields.fields(fields.toArray(new String[0]));
+	}
 }

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

@@ -81,6 +81,15 @@ public FieldReference getReference(String name) {
 		return getReference(null, name);
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getFields(java.lang.Class)
+	 */
+	@Override
+	public Fields getFields(Class<?> type) {
+		return rootContext.getFields(type);
+	}
+
 	/**
 	 * Returns a {@link FieldReference} to the given {@link Field} with the given {@code name}.
 	 *

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

@@ -78,4 +78,13 @@ public FieldReference getReference(Field field) {
 	public FieldReference getReference(String name) {
 		return new ExpressionFieldReference(delegate.getReference(name));
 	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getFields(java.lang.Class)
+	 */
+	@Override
+	public Fields getFields(Class<?> type) {
+		return delegate.getFields(type);
+	}
 }

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

@@ -91,6 +91,15 @@ public FieldReference getReference(String name) {
 		return delegate.getReference(name);
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getFields(java.lang.Class)
+	 */
+	@Override
+	public Fields getFields(Class<?> type) {
+		return delegate.getFields(type);
+	}
+
 	@SuppressWarnings("unchecked")
 	private Document doPrefix(Document source) {
 

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

@@ -30,6 +30,7 @@
 import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ReflectionUtils;
 
 /**
  * Encapsulates the aggregation framework {@code $project}-operation.
@@ -73,6 +74,16 @@ public ProjectionOperation(Fields fields) {
 		this(NONE, ProjectionOperationBuilder.FieldProjection.from(fields));
 	}
 
+	/**
+	 * Creates a new {@link ProjectionOperation} including all top level fields of the given {@link Class type}.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @since 2.2
+	 */
+	public ProjectionOperation(Class<?> type) {
+		this(NONE, Collections.singletonList(new TypeProjection(type)));
+	}
+
 	/**
 	 * Copy constructor to allow building up {@link ProjectionOperation} instances from already existing
 	 * {@link Projection}s.
@@ -1700,4 +1711,36 @@ public Document toDocument(AggregationOperationContext context) {
 			return new Document(field.getName(), expression.toDocument(context));
 		}
 	}
+
+	/**
+	 * A {@link Projection} including all top level fields of the given target type mapped to include potentially
+	 * deviating field names.
+	 *
+	 * @since 2.2
+	 * @author Christoph Strobl
+	 */
+	static class TypeProjection extends Projection {
+
+		private final Class<?> type;
+
+		TypeProjection(Class<?> type) {
+
+			super(Fields.field(type.getSimpleName()));
+			this.type = type;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.Projection#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+
+			Document projections = new Document();
+
+			Fields fields = context.getFields(type);
+			fields.asList().forEach(it -> projections.append(it.getName(), 1));
+			return context.getMappedObject(projections, type);
+		}
+	}
 }

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

@@ -17,9 +17,12 @@
 
 import static org.springframework.data.mongodb.core.aggregation.Fields.*;
 
+import java.util.ArrayList;
+import java.util.List;
+
 import org.bson.Document;
 import org.springframework.data.mapping.PersistentPropertyPath;
-import org.springframework.data.mapping.PropertyPath;
+import org.springframework.data.mapping.SimplePropertyHandler;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
@@ -101,6 +104,23 @@ public FieldReference getReference(String name) {
 		return getReferenceFor(field(name));
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getFields(java.lang.Class)
+	 */
+	@Override
+	public Fields getFields(Class<?> type) {
+
+		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(type);
+		if (entity == null) {
+			return AggregationOperationContext.super.getFields(type);
+		}
+
+		List<String> fields = new ArrayList<>();
+		entity.doWithProperties((SimplePropertyHandler) it -> fields.add(it.getName()));
+		return Fields.fields(fields.toArray(new String[fields.size()]));
+	}
+
 	private FieldReference getReferenceFor(Field field) {
 
 		PersistentPropertyPath<MongoPersistentProperty> propertyPath = mappingContext

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

@@ -41,6 +41,12 @@
 import org.springframework.data.mongodb.core.aggregation.ProjectionOperation.ProjectionOperationBuilder;
 import org.springframework.data.mongodb.core.aggregation.StringOperators.Concat;
 import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
+import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
+import org.springframework.data.mongodb.core.convert.MongoConverter;
+import org.springframework.data.mongodb.core.convert.NoOpDbRefResolver;
+import org.springframework.data.mongodb.core.convert.QueryMapper;
+import org.springframework.data.mongodb.core.mapping.Field;
+import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
 
 /**
  * Unit tests for {@link ProjectionOperation}.
@@ -61,7 +67,7 @@ public class ProjectionOperationUnitTests {
 
 	@Test(expected = IllegalArgumentException.class) // DATAMONGO-586
 	public void rejectsNullFields() {
-		new ProjectionOperation(null);
+		new ProjectionOperation((Fields) null);
 	}
 
 	@Test // DATAMONGO-586
@@ -2099,6 +2105,60 @@ public void shouldRenderDateFromStringWithFormat() {
 				"{ $project : { newDate: { $dateFromString: { dateString : \"2017-02-08T12:10:40.787\", format : \"dd/mm/yyyy\" } } } }"));
 	}
 
+	@Test // DATAMONGO-2200
+	public void typeProjectionShouldIncludeTopLevelFieldsOfType() {
+
+		ProjectionOperation operation = Aggregation.project(Book.class);
+
+		Document document = operation.toDocument(Aggregation.DEFAULT_CONTEXT);
+		Document projectClause = DocumentTestUtils.getAsDocument(document, PROJECT);
+
+		assertThat(projectClause) //
+				.hasSize(2) //
+				.containsEntry("title", 1) //
+				.containsEntry("author", 1);
+	}
+
+	@Test // DATAMONGO-2200
+	public void typeProjectionShouldMapFieldNames() {
+
+		MongoMappingContext mappingContext = new MongoMappingContext();
+		MongoConverter converter = new MappingMongoConverter(NoOpDbRefResolver.INSTANCE, mappingContext);
+
+		Document document = Aggregation.project(BookRenamed.class)
+				.toDocument(new TypeBasedAggregationOperationContext(Book.class, mappingContext, new QueryMapper(converter)));
+		Document projectClause = DocumentTestUtils.getAsDocument(document, PROJECT);
+
+		assertThat(projectClause) //
+				.hasSize(2) //
+				.containsEntry("ti_tl_e", 1) //
+				.containsEntry("author", 1);
+	}
+
+	@Test // DATAMONGO-2200
+	public void typeProjectionShouldIncludeInterfaceProjectionValues() {
+
+		ProjectionOperation operation = Aggregation.project(ProjectionInterface.class);
+
+		Document document = operation.toDocument(Aggregation.DEFAULT_CONTEXT);
+		Document projectClause = DocumentTestUtils.getAsDocument(document, PROJECT);
+
+		assertThat(projectClause) //
+				.hasSize(1) //
+				.containsEntry("title", 1);
+	}
+
+	@Test // DATAMONGO-2200
+	public void typeProjectionShouldBeEmptyIfNoPropertiesFound() {
+
+		ProjectionOperation operation = Aggregation.project(EmptyType.class);
+
+		Document document = operation.toDocument(Aggregation.DEFAULT_CONTEXT);
+		Document projectClause = DocumentTestUtils.getAsDocument(document, PROJECT);
+
+		assertThat(projectClause).isEmpty();
+	}
+
 	private static Document exctractOperation(String field, Document fromProjectClause) {
 		return (Document) fromProjectClause.get(field);
 	}
@@ -2109,11 +2169,25 @@ static class Book {
 		Author author;
 	}
 
+	@Data
+	static class BookRenamed {
+		@Field("ti_tl_e") String title;
+		Author author;
+	}
+
 	@Data
 	static class Author {
 		String first;
 		String last;
 		String middle;
 	}
 
+	interface ProjectionInterface {
+		String getTitle();
+	}
+
+	static class EmptyType {
+
+	}
+
 }