DATAKV-101 - Favor Iterable over Collection types for KeyValueOperations.

Change return types for Adapter and Operations from Collection types to Iterable. Added count(keyspace) to KeyValueAdapter.

Original pull request: #8.

Author: christophstrobl

src/main/java/org/springframework/data/keyvalue/core/IterableConverter.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://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.keyvalue.core;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Converter capable of transforming a given {@link Iterable} into a collection type.
+ * 
+ * @author Christoph Strobl
+ * @param <T>
+ */
+public final class IterableConverter {
+
+	private IterableConverter() {}
+
+	/**
+	 * Converts a given {@link Iterable} into a {@link List}
+	 * 
+	 * @param source
+	 * @return {@link Collections#emptyList()} when source is {@literal null}.
+	 */
+	public static <T> List<T> toList(Iterable<T> source) {
+
+		if (source == null) {
+			return Collections.emptyList();
+		}
+
+		if (source instanceof List) {
+			return (List<T>) source;
+		}
+
+		if (source instanceof Collection) {
+			return new ArrayList<T>((Collection<T>) source);
+		}
+
+		List<T> result = new ArrayList<T>();
+		for (T value : source) {
+			result.add(value);
+		}
+		return result;
+	}
+}

src/main/java/org/springframework/data/keyvalue/core/KeyValueAdapter.java

@@ -71,7 +71,7 @@ public interface KeyValueAdapter extends DisposableBean {
 	 * @param keyspace must not be {@literal null}.
 	 * @return empty {@link Collection} if nothing found.
 	 */
-	Collection<?> getAllOf(Serializable keyspace);
+	Iterable<?> getAllOf(Serializable keyspace);
 
 	/**
 	 * Returns a {@link KeyValueIterator} that iterates over all entries. 
@@ -100,7 +100,14 @@ public interface KeyValueAdapter extends DisposableBean {
 	 * @param keyspace must not be {@literal null}.
 	 * @return empty {@link Collection} if no match found.
 	 */
-	Collection<?> find(KeyValueQuery<?> query, Serializable keyspace);
+	Iterable<?> find(KeyValueQuery<?> query, Serializable keyspace);
+
+	/**
+	 * Count number of objects within {@literal keyspace}.
+	 * 
+	 * @param keyspace must not be {@literal null}.
+	 */
+	long count(Serializable keyspace);
 
 	/**
 	 * Count all matching objects within {@literal keyspace}.

src/main/java/org/springframework/data/keyvalue/core/KeyValueOperations.java

@@ -16,7 +16,6 @@
 package org.springframework.data.keyvalue.core;
 
 import java.io.Serializable;
-import java.util.List;
 
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.data.domain.Sort;
@@ -52,9 +51,9 @@ public interface KeyValueOperations extends DisposableBean {
 	 * assigned to requested type.
 	 * 
 	 * @param type must not be {@literal null}.
-	 * @return empty collection if no elements found.
+	 * @return empty iterable if no elements found.
 	 */
-	<T> List<T> findAll(Class<T> type);
+	<T> Iterable<T> findAll(Class<T> type);
 
 	/**
 	 * Get all elements ordered by sort. Respects {@link KeySpace} if present and therefore returns all elements that can
@@ -64,7 +63,7 @@ public interface KeyValueOperations extends DisposableBean {
 	 * @param type must not be {@literal null}.
 	 * @return
 	 */
-	<T> List<T> findAll(Sort sort, Class<T> type);
+	<T> Iterable<T> findAll(Sort sort, Class<T> type);
 
 	/**
 	 * Get element of given type with given id. Respects {@link KeySpace} if present and therefore returns all elements
@@ -90,9 +89,9 @@ public interface KeyValueOperations extends DisposableBean {
 	 * 
 	 * @param query must not be {@literal null}.
 	 * @param type must not be {@literal null}.
-	 * @return empty collection if no match found.
+	 * @return empty iterable if no match found.
 	 */
-	<T> List<T> find(KeyValueQuery<?> query, Class<T> type);
+	<T> Iterable<T> find(KeyValueQuery<?> query, Class<T> type);
 
 	/**
 	 * Get all elements in given range. Respects {@link KeySpace} if present and therefore returns all elements that can
@@ -103,7 +102,7 @@ public interface KeyValueOperations extends DisposableBean {
 	 * @param type must not be {@literal null}.
 	 * @return
 	 */
-	<T> List<T> findInRange(int offset, int rows, Class<T> type);
+	<T> Iterable<T> findInRange(int offset, int rows, Class<T> type);
 
 	/**
 	 * Get all elements in given range ordered by sort. Respects {@link KeySpace} if present and therefore returns all
@@ -115,7 +114,7 @@ public interface KeyValueOperations extends DisposableBean {
 	 * @param type
 	 * @return
 	 */
-	<T> List<T> findInRange(int offset, int rows, Sort sort, Class<T> type);
+	<T> Iterable<T> findInRange(int offset, int rows, Sort sort, Class<T> type);
 
 	/**
 	 * @param objectToUpdate must not be {@literal null}.

src/main/java/org/springframework/data/keyvalue/core/KeyValueTemplate.java

@@ -19,7 +19,6 @@
 
 import java.io.Serializable;
 import java.util.ArrayList;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
@@ -203,14 +202,14 @@ public <T> List<T> findAll(final Class<T> type) {
 			@Override
 			public List<T> doInKeyValue(KeyValueAdapter adapter) {
 
-				Collection<?> x = adapter.getAllOf(resolveKeySpace(type));
+				Iterable<?> values = adapter.getAllOf(resolveKeySpace(type));
 
 				if (getKeySpace(type) == null) {
-					return new ArrayList<T>((Collection<T>) x);
+					return new ArrayList<T>(IterableConverter.toList((Iterable<T>) values));
 				}
 
 				ArrayList<T> filtered = new ArrayList<T>();
-				for (Object candidate : x) {
+				for (Object candidate : values) {
 					if (typeCheck(type, candidate)) {
 						filtered.add((T) candidate);
 					}
@@ -332,7 +331,7 @@ public T doInKeyValue(KeyValueAdapter adapter) {
 	public long count(Class<?> type) {
 
 		Assert.notNull(type, "Type for count must not be null!");
-		return findAll(type).size();
+		return adapter.count(resolveKeySpace(type));
 	}
 
 	/*
@@ -364,10 +363,10 @@ public <T> List<T> find(final KeyValueQuery<?> query, final Class<T> type) {
 			@Override
 			public List<T> doInKeyValue(KeyValueAdapter adapter) {
 
-				Collection<?> result = adapter.find(query, resolveKeySpace(type));
+				Iterable<?> result = adapter.find(query, resolveKeySpace(type));
 
 				if (getKeySpace(type) == null) {
-					return new ArrayList<T>((Collection<T>) result);
+					return new ArrayList<T>(IterableConverter.toList((Iterable<T>) result));
 				}
 
 				List<T> filtered = new ArrayList<T>();
@@ -517,7 +516,7 @@ private RuntimeException resolveExceptionIfPossible(RuntimeException e) {
 	}
 
 	private void potentiallyPublishEvent(KeyValueEvent event) {
-		
+
 		if (eventPublisher == null) {
 			return;
 		}

src/main/java/org/springframework/data/keyvalue/core/SpelQueryEngine.java

@@ -65,10 +65,10 @@ public long count(SpelExpression criteria, Serializable keyspace) {
 	}
 
 	@SuppressWarnings({ "unchecked", "rawtypes" })
-	private List<?> sortAndFilterMatchingRange(Collection<?> source, SpelExpression criteria, Comparator sort,
-			int offset, int rows) {
+	private List<?> sortAndFilterMatchingRange(Iterable<?> source, SpelExpression criteria, Comparator sort, int offset,
+			int rows) {
 
-		List<?> tmp = new ArrayList(source);
+		List<?> tmp = IterableConverter.toList(source);
 		if (sort != null) {
 			Collections.sort(tmp, sort);
 		}

src/main/java/org/springframework/data/keyvalue/repository/query/KeyValuePartTreeQuery.java

@@ -16,11 +16,11 @@
 package org.springframework.data.keyvalue.repository.query;
 
 import java.lang.reflect.Constructor;
-import java.util.List;
 
 import org.springframework.beans.BeanUtils;
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
+import org.springframework.data.keyvalue.core.IterableConverter;
 import org.springframework.data.keyvalue.core.KeyValueOperations;
 import org.springframework.data.keyvalue.core.query.KeyValueQuery;
 import org.springframework.data.repository.query.EvaluationContextProvider;
@@ -33,7 +33,6 @@
 import org.springframework.expression.EvaluationContext;
 import org.springframework.expression.spel.standard.SpelExpression;
 import org.springframework.util.ClassUtils;
-import org.springframework.util.CollectionUtils;
 
 /**
  * {@link RepositoryQuery} implementation deriving queries from {@link PartTree} using a predefined
@@ -77,21 +76,21 @@ public Object execute(Object[] parameters) {
 			query.setOffset(page.getOffset());
 			query.setRows(page.getPageSize());
 
-			List<?> result = this.keyValueOperations.find(query, queryMethod.getEntityInformation().getJavaType());
+			Iterable<?> result = this.keyValueOperations.find(query, queryMethod.getEntityInformation().getJavaType());
 
 			long count = queryMethod.isSliceQuery() ? 0 : keyValueOperations.count(query, queryMethod.getEntityInformation()
 					.getJavaType());
 
-			return new PageImpl(result, page, count);
+			return new PageImpl(IterableConverter.toList(result), page, count);
 
 		} else if (queryMethod.isCollectionQuery()) {
 
 			return this.keyValueOperations.find(query, queryMethod.getEntityInformation().getJavaType());
 
 		} else if (queryMethod.isQueryForEntity()) {
 
-			List<?> result = this.keyValueOperations.find(query, queryMethod.getEntityInformation().getJavaType());
-			return CollectionUtils.isEmpty(result) ? null : result.get(0);
+			Iterable<?> result = this.keyValueOperations.find(query, queryMethod.getEntityInformation().getJavaType());
+			return result.iterator().hasNext() ? result.iterator().next() : null;
 
 		}
 

src/main/java/org/springframework/data/keyvalue/repository/support/SimpleKeyValueRepository.java

@@ -23,6 +23,7 @@
 import org.springframework.data.domain.PageImpl;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
+import org.springframework.data.keyvalue.core.IterableConverter;
 import org.springframework.data.keyvalue.core.KeyValueOperations;
 import org.springframework.data.keyvalue.repository.KeyValueRepository;
 import org.springframework.data.repository.core.EntityInformation;
@@ -76,12 +77,11 @@ public Page<T> findAll(Pageable pageable) {
 			return new PageImpl<T>(result, null, result.size());
 		}
 
-		List<T> content = null;
-
-		content = operations.findInRange(pageable.getOffset(), pageable.getPageSize(), pageable.getSort(),
+		Iterable<T> content = operations.findInRange(pageable.getOffset(), pageable.getPageSize(), pageable.getSort(),
 				entityInformation.getJavaType());
 
-		return new PageImpl<T>(content, pageable, this.operations.count(entityInformation.getJavaType()));
+		return new PageImpl<T>(IterableConverter.toList(content), pageable, this.operations.count(entityInformation
+				.getJavaType()));
 	}
 
 	/*
@@ -139,7 +139,7 @@ public boolean exists(ID id) {
 	 */
 	@Override
 	public List<T> findAll() {
-		return operations.findAll(entityInformation.getJavaType());
+		return IterableConverter.toList(operations.findAll(entityInformation.getJavaType()));
 	}
 
 	/*

src/main/java/org/springframework/data/map/MapKeyValueAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 the original author or authors.
+ * Copyright 2014-2015 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.
@@ -104,6 +104,15 @@ public boolean contains(Serializable id, Serializable keyspace) {
 		return get(id, keyspace) != null;
 	}
 
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.keyvalue.core.KeyValueAdapter#count(java.io.Serializable)
+	 */
+	@Override
+	public long count(Serializable keyspace) {
+		return getKeySpaceMap(keyspace).size();
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.keyvalue.core.KeyValueAdapter#get(java.io.Serializable, java.io.Serializable)