DATAMONGO-636 - Added support for countBy in derived queries.

We now change the query execution to a count execution in case a derived query has the PartTree.isCountProjection() set to true or a query defined in @Query has the newly introduced count() attribute set to true.

As the native Mongo count() returns a long we use a default ConversionService to potentially massage the query result into other numerical types.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 the original author or authors.
+ * Copyright 2011-2013 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.
@@ -15,7 +15,11 @@
  */
 package org.springframework.data.mongodb.repository;
 
-import java.lang.annotation.*;
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
 
 /**
  * Annotation to declare finder queries directly on repository methods. Both attributes allow using a placeholder
@@ -43,4 +47,12 @@ public @interface Query {
 	 * @return
 	 */
 	String fields() default "";
+
+	/**
+	 * Returns whether the query defined should be executed as count projection.
+	 * 
+	 * @since 1.3
+	 * @return
+	 */
+	boolean count() default false;
 }

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

@@ -17,6 +17,8 @@ package org.springframework.data.mongodb.repository.query;
 
 import java.util.List;
 
+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.mongodb.core.MongoOperations;
@@ -39,6 +41,8 @@ import org.springframework.util.Assert;
  */
 public abstract class AbstractMongoQuery implements RepositoryQuery {
 
+	private static final ConversionService CONVERSION_SERVICE = new DefaultConversionService();
+
 	private final MongoQueryMethod method;
 	private final MongoOperations operations;
 
@@ -86,9 +90,33 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 			return new CollectionExecution(accessor.getPageable()).execute(query);
 		} else if (method.isPageQuery()) {
 			return new PagedExecution(accessor.getPageable()).execute(query);
-		} else {
-			return new SingleEntityExecution().execute(query);
 		}
+
+		Object result = new SingleEntityExecution(isCountQuery()).execute(query);
+
+		if (result == null) {
+			return result;
+		}
+
+		Class<?> expectedReturnType = method.getReturnType().getType();
+
+		if (expectedReturnType.isAssignableFrom(result.getClass())) {
+			return result;
+		}
+
+		return CONVERSION_SERVICE.convert(result, expectedReturnType);
+	}
+
+	/**
+	 * Creates a {@link Query} instance using the given {@link ConvertingParameterAccessor}. Will delegate to
+	 * {@link #createQuery(ConvertingParameterAccessor)} by default but allows customization of the count query to be
+	 * triggered.
+	 * 
+	 * @param accessor must not be {@literal null}.
+	 * @return
+	 */
+	protected Query createCountQuery(ConvertingParameterAccessor accessor) {
+		return createQuery(accessor);
 	}
 
 	/**
@@ -100,16 +128,11 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 	protected abstract Query createQuery(ConvertingParameterAccessor accessor);
 
 	/**
-	 * Creates a {@link Query} instance using the given {@link ConvertingParameterAccessor}. Will delegate to
-	 * {@link #createQuery(ConvertingParameterAccessor)} by default but allows customization of the count query to be
-	 * triggered.
+	 * Returns whether the query should get a count projection applied.
 	 * 
-	 * @param accessor must not be {@literal null}.
 	 * @return
 	 */
-	protected Query createCountQuery(ConvertingParameterAccessor accessor) {
-		return createQuery(accessor);
-	}
+	protected abstract boolean isCountQuery();
 
 	private abstract class Execution {
 
@@ -191,6 +214,12 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 	 */
 	class SingleEntityExecution extends Execution {
 
+		private final boolean countProjection;
+
+		private SingleEntityExecution(boolean countProjection) {
+			this.countProjection = countProjection;
+		}
+
 		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.repository.AbstractMongoQuery.Execution#execute(org.springframework.data.mongodb.core.core.query.Query)
@@ -199,7 +228,8 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		Object execute(Query query) {
 
 			MongoEntityMetadata<?> metadata = method.getEntityInformation();
-			return operations.findOne(query, metadata.getJavaType());
+			return countProjection ? operations.count(query, metadata.getJavaType()) : operations.findOne(query,
+					metadata.getJavaType());
 		}
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2012 the original author or authors.
+ * Copyright 2011-2013 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.
@@ -171,7 +171,7 @@ public class MongoQueryMethod extends QueryMethod {
 	 * 
 	 * @return
 	 */
-	private Query getQueryAnnotation() {
+	Query getQueryAnnotation() {
 		return method.getAnnotation(Query.class);
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2010 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -77,4 +77,13 @@ public class PartTreeMongoQuery extends AbstractMongoQuery {
 	protected Query createCountQuery(ConvertingParameterAccessor accessor) {
 		return new MongoQueryCreator(tree, accessor, context, false).createQuery();
 	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.repository.query.AbstractMongoQuery#isCountQuery()
+	 */
+	@Override
+	protected boolean isCountQuery() {
+		return tree.isCountProjection();
+	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2012 the original author or authors.
+ * Copyright 2011-2013 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.
@@ -38,17 +38,21 @@ public class StringBasedMongoQuery extends AbstractMongoQuery {
 
 	private final String query;
 	private final String fieldSpec;
+	private final boolean isCountQuery;
 
 	/**
 	 * Creates a new {@link StringBasedMongoQuery}.
 	 * 
-	 * @param method
-	 * @param template
+	 * @param method must not be {@literal null}.
+	 * @param template must not be {@literal null}.
 	 */
 	public StringBasedMongoQuery(String query, MongoQueryMethod method, MongoOperations mongoOperations) {
+
 		super(method, mongoOperations);
+
 		this.query = query;
 		this.fieldSpec = method.getFieldSpecification();
+		this.isCountQuery = method.hasAnnotatedQuery() ? method.getQueryAnnotation().count() : false;
 	}
 
 	public StringBasedMongoQuery(MongoQueryMethod method, MongoOperations mongoOperations) {
@@ -82,6 +86,15 @@ public class StringBasedMongoQuery extends AbstractMongoQuery {
 		return query;
 	}
 
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.repository.query.AbstractMongoQuery#isCountQuery()
+	 */
+	@Override
+	protected boolean isCountQuery() {
+		return isCountQuery;
+	}
+
 	private String replacePlaceholders(String input, ConvertingParameterAccessor accessor) {
 
 		Matcher matcher = PLACEHOLDER.matcher(input);

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

@@ -546,4 +546,28 @@ public abstract class AbstractPersonRepositoryIntegrationTests {
 		assertThat(result, hasSize(1));
 		assertThat(result, hasItem(dave));
 	}
+
+	/**
+	 * @see DATAMONGO-636
+	 */
+	@Test
+	public void executesDerivedCountProjection() {
+		assertThat(repository.countByLastname("Matthews"), is(2L));
+	}
+
+	/**
+	 * @see DATAMONGO-636
+	 */
+	@Test
+	public void executesDerivedCountProjectionToInt() {
+		assertThat(repository.countByFirstname("Oliver August"), is(1));
+	}
+
+	/**
+	 * @see DATAMONGO-636
+	 */
+	@Test
+	public void executesAnnotatedCountProjection() {
+		assertThat(repository.someCountQuery("Matthews"), is(2L));
+	}
 }

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

@@ -198,4 +198,20 @@ public interface PersonRepository extends MongoRepository<Person, String>, Query
 	 * @return
 	 */
 	List<Person> findByCredentials(Credentials credentials);
+
+	/**
+	 * @see DATAMONGO-636
+	 */
+	long countByLastname(String lastname);
+
+	/**
+	 * @see DATAMONGO-636
+	 */
+	int countByFirstname(String firstname);
+
+	/**
+	 * @see DATAMONGO-636
+	 */
+	@Query(value = "{ 'lastname' : ?0 }", count = true)
+	long someCountQuery(String lastname);
 }