DATAKV-197 - Polishing.

Update JavaDoc, fix trailing whitespace and add missing @Nullable annotations to methods potentially returning null values.

Original Pull Request:#28

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

@@ -16,6 +16,7 @@
 package org.springframework.data.keyvalue.core;
 
 import org.springframework.data.keyvalue.core.query.KeyValueQuery;
+import org.springframework.lang.Nullable;
 
 /**
  * Resolves the criteria object from given {@link KeyValueQuery}.
@@ -31,9 +32,10 @@ public interface CriteriaAccessor<T> {
 	 * transformation to match the desired type.
 	 *
 	 * @param query must not be {@literal null}.
-	 * @return the criteria extracted from the query.
+	 * @return the criteria extracted from the query. Can be {@literal null}.
 	 * @throws IllegalArgumentException in case the criteria is not valid for usage with specific
 	 *           {@link CriteriaAccessor}.
 	 */
+	@Nullable
 	T resolve(KeyValueQuery<?> query);
 }

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

@@ -348,7 +348,7 @@ public class KeyValueTemplate implements KeyValueOperations, ApplicationEventPub
 
 	/**
 	 * Execute {@link KeyValueCallback} and require a non-{@literal null} return value.
-	 * 
+	 *
 	 * @param action
 	 * @param <T>
 	 * @return

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

@@ -17,6 +17,7 @@ package org.springframework.data.keyvalue.core;
 
 import org.springframework.data.domain.Sort;
 import org.springframework.data.keyvalue.core.query.KeyValueQuery;
+import org.springframework.lang.Nullable;
 
 /**
  * Resolves the {@link Sort} object from given {@link KeyValueQuery} and potentially converts it into a store specific
@@ -35,5 +36,6 @@ public interface SortAccessor<T> {
 	 * @param query must not be {@literal null}.
 	 * @return {@literal null} in case {@link Sort} has not been defined on {@link KeyValueQuery}.
 	 */
+	@Nullable
 	T resolve(KeyValueQuery<?> query);
 }

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

@@ -52,7 +52,7 @@ class SpelQueryEngine extends QueryEngine<KeyValueAdapter, SpelCriteria, Compara
 	 * @see org.springframework.data.keyvalue.core.QueryEngine#execute(java.lang.Object, java.lang.Object, int, int, java.lang.String)
 	 */
 	@Override
-	public Collection<?> execute(SpelCriteria criteria, Comparator<?> sort, long offset, int rows, String keyspace) {
+	public Collection<?> execute(@Nullable SpelCriteria criteria, @Nullable Comparator<?> sort, long offset, int rows, String keyspace) {
 		return sortAndFilterMatchingRange(getRequiredAdapter().getAllOf(keyspace), criteria, sort, offset, rows);
 	}
 
@@ -61,13 +61,13 @@ class SpelQueryEngine extends QueryEngine<KeyValueAdapter, SpelCriteria, Compara
 	 * @see org.springframework.data.keyvalue.core.QueryEngine#count(java.lang.Object, java.lang.String)
 	 */
 	@Override
-	public long count(SpelCriteria criteria, String keyspace) {
+	public long count(@Nullable SpelCriteria criteria, String keyspace) {
 		return filterMatchingRange(IterableConverter.toList(getRequiredAdapter().getAllOf(keyspace)), criteria, -1, -1)
 				.size();
 	}
 
 	@SuppressWarnings("unchecked")
-	private List<?> sortAndFilterMatchingRange(Iterable<?> source, SpelCriteria criteria, @Nullable Comparator sort,
+	private List<?> sortAndFilterMatchingRange(Iterable<?> source, @Nullable SpelCriteria criteria, @Nullable Comparator sort,
 			long offset, int rows) {
 
 		List<?> tmp = IterableConverter.toList(source);

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

@@ -20,7 +20,7 @@ import org.springframework.dao.UncategorizedDataAccessException;
 /**
  * Normal superclass when we can't distinguish anything more specific than "something went wrong with the underlying
  * resource".
- * 
+ *
  * @author Christoph Strobl
  * @author Mark Paluch
  */
@@ -30,7 +30,7 @@ public class UncategorizedKeyValueException extends UncategorizedDataAccessExcep
 
 	/**
 	 * Creates a new {@link UncategorizedKeyValueException}.
-	 * 
+	 *
 	 * @param msg the detail message.
 	 * @param cause the root cause (usually from using a underlying data access API).
 	 */

src/main/java/org/springframework/data/keyvalue/core/event/KeyValueEvent.java

@@ -347,8 +347,9 @@ public class KeyValueEvent<T> extends ApplicationEvent {
 		/**
 		 * Get the current value.
 		 *
-		 * @return
+		 * @return can be {@literal null}.
 		 */
+		@Nullable
 		public T after() {
 			return getPayload();
 		}

src/main/java/org/springframework/data/keyvalue/core/mapping/BasicKeyValuePersistentEntity.java

@@ -33,7 +33,7 @@ public class BasicKeyValuePersistentEntity<T, P extends KeyValuePersistentProper
 
 	private static final KeySpaceResolver DEFAULT_FALLBACK_RESOLVER = ClassNameKeySpaceResolver.INSTANCE;
 
-	private final String keyspace;
+	private final @Nullable String keyspace;
 
 	/**
 	 * @param information must not be {@literal null}.
@@ -47,6 +47,7 @@ public class BasicKeyValuePersistentEntity<T, P extends KeyValuePersistentProper
 		this.keyspace = detectKeySpace(information.getType(), fallbackKeySpaceResolver);
 	}
 
+	@Nullable
 	private static String detectKeySpace(Class<?> type, @Nullable KeySpaceResolver fallback) {
 
 		String keySpace = AnnotationBasedKeySpaceResolver.INSTANCE.resolveKeySpace(type);

src/main/java/org/springframework/data/keyvalue/core/mapping/KeyValuePersistentEntity.java

@@ -16,6 +16,7 @@
 package org.springframework.data.keyvalue.core.mapping;
 
 import org.springframework.data.mapping.model.MutablePersistentEntity;
+import org.springframework.lang.Nullable;
 
 /**
  * @author Christoph Strobl
@@ -27,7 +28,8 @@ public interface KeyValuePersistentEntity<T, P extends KeyValuePersistentPropert
 	/**
 	 * Get the {@literal keySpace} a given entity assigns to.
 	 * 
-	 * @return never {@literal null}.
+	 * @return can be {@literal null}.
 	 */
+	@Nullable
 	String getKeySpace();
 }