DATAMONGO-1761 - Add distinct(…) method for MongoTemplate.

Original Pull Request: #494

Author: eric

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

@@ -24,19 +24,8 @@
 import lombok.RequiredArgsConstructor;
 
 import java.io.IOException;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.LinkedHashSet;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.Map.Entry;
-import java.util.Optional;
-import java.util.Scanner;
-import java.util.Set;
 import java.util.concurrent.TimeUnit;
 
 import org.bson.Document;
@@ -127,15 +116,12 @@
 import org.springframework.util.ResourceUtils;
 import org.springframework.util.StringUtils;
 
-import com.mongodb.Cursor;
-import com.mongodb.DBCollection;
-import com.mongodb.DBCursor;
-import com.mongodb.Mongo;
 import com.mongodb.MongoClient;
 import com.mongodb.MongoException;
 import com.mongodb.ReadPreference;
 import com.mongodb.WriteConcern;
 import com.mongodb.client.AggregateIterable;
+import com.mongodb.client.DistinctIterable;
 import com.mongodb.client.FindIterable;
 import com.mongodb.client.MapReduceIterable;
 import com.mongodb.client.MongoCollection;
@@ -173,6 +159,7 @@
  * @author Laszlo Csontos
  * @author Maninder Singh
  * @author Borislav Rangelov
+ * @author duozhilin
  */
 @SuppressWarnings("deprecation")
 public class MongoTemplate implements MongoOperations, ApplicationContextAware, IndexOperationsProvider {
@@ -808,6 +795,30 @@ public <T> T findById(Object id, Class<T> entityClass, String collectionName) {
 		return doFindOne(collectionName, new Document(idKey, id), new Document(), entityClass);
 	}
 
+	public <T, Z> List<T> distinct(String field, Class<Z> entityClass, Class<T> resultClass) {
+		return distinct(new Query(), field, determineCollectionName(entityClass), resultClass);
+	}
+
+	public <T, Z> List<T> distinct(Query query, String field, Class<Z> entityClass, Class<T> resultClass) {
+		return distinct(query, field, determineCollectionName(entityClass), resultClass);
+	}
+
+	public <T> List<T> distinct(Query query, String field, String collectionName, Class<T> resultClass) {
+		MongoCollection<Document> collection = this.getCollection(collectionName);
+		DistinctIterable<T> iterable = collection.distinct(field, query.getQueryObject(), resultClass);
+
+		MongoCursor<T> cursor = iterable.iterator();
+
+		List<T> result = new ArrayList<T>();
+
+		while (cursor.hasNext()) {
+			T object = cursor.next();
+			result.add(object);
+		}
+
+		return result;
+	}
+
 	@Override
 	public <T> GeoResults<T> geoNear(NearQuery near, Class<T> entityClass) {
 		return geoNear(near, entityClass, determineCollectionName(entityClass));

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

@@ -33,18 +33,7 @@
 import java.lang.reflect.InvocationTargetException;
 import java.math.BigDecimal;
 import java.math.BigInteger;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Calendar;
-import java.util.Collections;
-import java.util.Date;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Locale;
-import java.util.Map;
-import java.util.UUID;
+import java.util.*;
 
 import org.bson.types.ObjectId;
 import org.hamcrest.collection.IsMapContaining;
@@ -122,6 +111,7 @@
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Laszlo Csontos
+ * @author duozhilin
  */
 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration("classpath:infrastructure.xml")
@@ -749,6 +739,39 @@ public void testFindAndRemove() throws Exception {
 		assertThat(notFound, nullValue());
 	}
 
+	@Test
+	public void testDistinct() {
+		Address address1 = new Address();
+		address1.state = "PA";
+		address1.city = "Philadelphia";
+
+		Address address2 = new Address();
+		address2.state = "PA";
+		address2.city = " New York";
+
+		MyPerson person1 = new MyPerson();
+		person1.name = "Ben";
+		person1.address = address1;
+
+		MyPerson person2 = new MyPerson();
+		person2.name = "Eric";
+		person2.address = address2;
+
+		template.save(person1);
+		template.save(person2);
+
+		List<String> nameList = template.distinct("name", MyPerson.class, String.class);
+		assertTrue(nameList.containsAll(Arrays.asList(person1.getName(), person2.getName())));
+
+		Query query = new BasicQuery("{'address.state' : 'PA'}");
+		nameList = template.distinct(query, "name", MyPerson.class, String.class);
+		assertTrue(nameList.containsAll(Arrays.asList(person1.getName(), person2.getName())));
+
+		String collectionName = template.determineCollectionName(MyPerson.class);
+		nameList = template.distinct(query, "name", collectionName, String.class);
+		assertTrue(nameList.containsAll(Arrays.asList(person1.getName(), person2.getName())));
+	}
+
 	@Test
 	public void testUsingAnInQueryWithObjectId() throws Exception {