DATAMONGO-1165 - Add support for Java 8 Stream as return type for repository methods.

Added support for a MongoDB Cursor backed Iterator that allows the usage of a Java 8 Stream at the repository level.

Original pull request: #274.

Author: Thomas Darimont

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

@@ -33,8 +33,10 @@
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
+import org.springframework.data.util.CloseableIterator;
 
 import com.mongodb.CommandResult;
+import com.mongodb.Cursor;
 import com.mongodb.DB;
 import com.mongodb.DBCollection;
 import com.mongodb.DBObject;
@@ -165,6 +167,20 @@ public interface MongoOperations {
 	@Deprecated
 	<T> T executeInSession(DbCallback<T> action);
 
+	/**
+	 * Executes the given {@link Query} on the entity collection of the specified {@code entityType} backed by a Mongo DB
+	 * {@link Cursor}.
+	 * <p>
+	 * Returns a {@link CloseableIterator} that wraps the a Mongo DB {@link Cursor} that needs to be closed.
+	 * 
+	 * @param <T> element return type
+	 * @param query
+	 * @param entityType
+	 * @return
+	 * @since 1.7
+	 */
+	<T> CloseableIterator<T> executeAsStream(Query query, Class<T> entityType);
+
 	/**
 	 * Create an uncapped collection with a name based on the provided entity class.
 	 * 

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

@@ -95,6 +95,8 @@
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
+import org.springframework.data.util.CloseableIterator;
+import org.springframework.data.mongodb.util.CloseableIterator;
 import org.springframework.data.mongodb.util.MongoClientVersion;
 import org.springframework.jca.cci.core.ConnectionCallback;
 import org.springframework.util.Assert;
@@ -106,6 +108,7 @@
 import com.mongodb.BasicDBObject;
 import com.mongodb.Bytes;
 import com.mongodb.CommandResult;
+import com.mongodb.Cursor;
 import com.mongodb.DB;
 import com.mongodb.DBCollection;
 import com.mongodb.DBCursor;
@@ -315,6 +318,31 @@ public MongoConverter getConverter() {
 		return this.mongoConverter;
 	}
 
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#executeAsStream(org.springframework.data.mongodb.core.query.Query, java.lang.Class)
+	 */
+	@Override
+	public <T> CloseableIterator<T> executeAsStream(final Query query, final Class<T> entityType) {
+
+		return execute(entityType, new CollectionCallback<CloseableIterator<T>>() {
+
+			@Override
+			public CloseableIterator<T> doInCollection(DBCollection collection) throws MongoException, DataAccessException {
+
+				MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(entityType);
+
+				DBObject mappedFields = queryMapper.getMappedFields(query.getFieldsObject(), persistentEntity);
+				DBObject mappedQuery = queryMapper.getMappedObject(query.getQueryObject(), persistentEntity);
+
+				DBCursor cursor = collection.find(mappedQuery, mappedFields);
+				ReadDbObjectCallback<T> readCallback = new ReadDbObjectCallback<T>(mongoConverter, entityType);
+
+				return new CloseableIterableCusorAdapter<T>(cursor, exceptionTranslator, readCallback);
+			}
+		});
+
+	}
+
 	public String getCollectionName(Class<?> entityClass) {
 		return this.determineCollectionName(entityClass);
 	}
@@ -2122,9 +2150,10 @@ public DBObject doInCollection(DBCollection collection) throws MongoException, D
 	 * Simple internal callback to allow operations on a {@link DBObject}.
 	 * 
 	 * @author Oliver Gierke
+	 * @author Thomas Darimont
 	 */
 
-	private interface DbObjectCallback<T> {
+	static interface DbObjectCallback<T> {
 
 		T doWith(DBObject object);
 	}
@@ -2287,4 +2316,76 @@ public GeoResult<T> doWith(DBObject object) {
 		}
 	}
 
+	/**
+	 * A {@link CloseableIterator} that is backed by a MongoDB {@link Cursor}.
+	 * 
+	 * @since 1.7
+	 * @author Thomas Darimont
+	 */
+	static class CloseableIterableCusorAdapter<T> implements CloseableIterator<T> {
+
+		private volatile Cursor cursor;
+		private PersistenceExceptionTranslator exceptionTranslator;
+		private DbObjectCallback<T> objectReadCallback;
+
+		/**
+		 * Creates a new {@link CloseableIterableCusorAdapter} backed by the given {@link Cursor}.
+		 * 
+		 * @param cursor
+		 * @param exceptionTranslator
+		 * @param objectReadCallback
+		 */
+		public CloseableIterableCusorAdapter(Cursor cursor, PersistenceExceptionTranslator exceptionTranslator,
+				DbObjectCallback<T> objectReadCallback) {
+
+			this.cursor = cursor;
+			this.exceptionTranslator = exceptionTranslator;
+			this.objectReadCallback = objectReadCallback;
+		}
+
+		@Override
+		public boolean hasNext() {
+
+			if (cursor == null) {
+				return false;
+			}
+
+			try {
+				return cursor.hasNext();
+			} catch (RuntimeException ex) {
+				throw exceptionTranslator.translateExceptionIfPossible(ex);
+			}
+		}
+
+		@Override
+		public T next() {
+
+			if (cursor == null) {
+				return null;
+			}
+
+			try {
+				DBObject item = cursor.next();
+				T converted = objectReadCallback.doWith(item);
+				return converted;
+			} catch (RuntimeException ex) {
+				throw exceptionTranslator.translateExceptionIfPossible(ex);
+			}
+		}
+
+		@Override
+		public void close() {
+
+			Cursor c = cursor;
+			try {
+				c.close();
+			} catch (RuntimeException ex) {
+				throw exceptionTranslator.translateExceptionIfPossible(ex);
+			} finally {
+				cursor = null;
+				exceptionTranslator = null;
+				objectReadCallback = null;
+			}
+		}
+	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractMongoQuery.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2014 the original author or authors.
+ * Copyright 2010-2015 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.
@@ -17,9 +17,10 @@
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Spliterator;
+import java.util.Spliterators;
+import java.util.stream.StreamSupport;
 
-import org.springframework.core.convert.ConversionService;
-import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Slice;
@@ -34,6 +35,8 @@
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.repository.query.ParameterAccessor;
 import org.springframework.data.repository.query.RepositoryQuery;
+import org.springframework.data.util.CloseableIterator;
+import org.springframework.data.util.CloseableIteratorDisposingRunnable;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.util.Assert;
 
@@ -48,8 +51,6 @@
  */
 public abstract class AbstractMongoQuery implements RepositoryQuery {
 
-	private static final ConversionService CONVERSION_SERVICE = new DefaultConversionService();
-
 	private final MongoQueryMethod method;
 	private final MongoOperations operations;
 
@@ -87,7 +88,9 @@ public Object execute(Object[] parameters) {
 
 		applyQueryMetaAttributesWhenPresent(query);
 
-		if (isDeleteQuery()) {
+		if (method.isStreamQuery()) {
+			return new StreamExecution().execute(query);
+		} else if (isDeleteQuery()) {
 			return new DeleteExecution().execute(query);
 		} else if (method.isGeoNearQuery() && method.isPageQuery()) {
 
@@ -415,4 +418,26 @@ private Object deleteAndConvertResult(Query query, MongoEntityMetadata<?> metada
 			return writeResult != null ? writeResult.getN() : 0L;
 		}
 	}
+
+	/**
+	 * @author Thomas Darimont
+	 * @since 1.7
+	 */
+	final class StreamExecution extends Execution {
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.repository.query.AbstractMongoQuery.Execution#execute(org.springframework.data.mongodb.core.query.Query)
+		 */
+		@Override
+		Object execute(Query query) {
+
+			Class<?> entityType = getQueryMethod().getEntityInformation().getJavaType();
+
+			@SuppressWarnings("unchecked")
+			CloseableIterator<Object> result = (CloseableIterator<Object>) operations.executeAsStream(query, entityType);
+			Spliterator<Object> spliterator = Spliterators.spliteratorUnknownSize(result, Spliterator.NONNULL);
+
+			return StreamSupport.stream(spliterator, false).onClose(new CloseableIteratorDisposingRunnable(result));
+		}
+	}
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/AbstractPersonRepositoryIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2014 the original author or authors.
+ * Copyright 2011-2015 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.
@@ -65,7 +65,7 @@ public abstract class AbstractPersonRepositoryIntegrationTests {
 
 	@Autowired MongoOperations operations;
 
-	Person dave, oliver, carter, boyd, stefan, leroi, alicia;
+	protected Person dave, oliver, carter, boyd, stefan, leroi, alicia;
 	QPerson person;
 
 	List<Person> all;

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/PersonRepository.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2014 the original author or authors.
+ * Copyright 2010-2015 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.
@@ -18,6 +18,7 @@
 import java.util.Collection;
 import java.util.Date;
 import java.util.List;
+import java.util.stream.Stream;
 
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
@@ -320,4 +321,10 @@ public interface PersonRepository extends MongoRepository<Person, String>, Query
 
 	@Query("{ ?0 : ?1 }")
 	List<Person> findByKeyValue(String key, String value);
+
+	/**
+	 * @see DATAMONGO-1165
+	 */
+	@Query("{firstname:{$in:?0}}")
+	Stream<Person> findByCustomQueryWithStreamingCursorByFirstnames(List<String> firstnames);
 }

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/PersonRepositoryIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2013 the original author or authors.
+ * Copyright 2010-2015 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.
@@ -15,6 +15,15 @@
  */
 package org.springframework.data.mongodb.repository;
 
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import org.junit.Test;
 import org.springframework.test.context.ContextConfiguration;
 
 /**
@@ -24,4 +33,21 @@
  * @author Thomas Darimont
  */
 @ContextConfiguration
-public class PersonRepositoryIntegrationTests extends AbstractPersonRepositoryIntegrationTests {}
+public class PersonRepositoryIntegrationTests extends AbstractPersonRepositoryIntegrationTests {
+
+	/**
+	 * @see DATAMONGO-1165
+	 */
+	@Test
+	public void shouldAllowReturningJava8StreamInCustomQuery() throws Exception {
+
+		Stream<Person> result = repository.findByCustomQueryWithStreamingCursorByFirstnames(Arrays.asList("Dave"));
+
+		try {
+			List<Person> readPersons = result.collect(Collectors.<Person> toList());
+			assertThat(readPersons, hasItems(dave));
+		} finally {
+			result.close();
+		}
+	}
+}