DATACMNS-525 - Introduce infrastructure for KeyValue repositories.

Added basic infrastructure for repositories on top of key-value data stores. For more details see the original pull request.

Original pull request: #95.

src/main/java/org/springframework/data/querydsl/QueryDslUtils.java

@@ -15,10 +15,26 @@
  */
 package org.springframework.data.querydsl;
 
+import java.util.ArrayList;
+import java.util.List;
+
+import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Sort.Order;
+import org.springframework.data.mapping.PropertyPath;
+import org.springframework.util.Assert;
+
+import com.mysema.query.support.Expressions;
+import com.mysema.query.types.Expression;
+import com.mysema.query.types.OrderSpecifier;
+import com.mysema.query.types.OrderSpecifier.NullHandling;
+import com.mysema.query.types.Path;
+import com.mysema.query.types.path.PathBuilder;
+
 /**
  * Utility class for Querydsl.
  * 
  * @author Oliver Gierke
+ * @author Christoph Strobl
  */
 public abstract class QueryDslUtils {
 
@@ -28,4 +44,96 @@ public abstract class QueryDslUtils {
 	private QueryDslUtils() {
 
 	}
+
+	/**
+	 * Transforms a plain {@link Order} into a QueryDsl specific {@link OrderSpecifier}.
+	 * 
+	 * @param sort
+	 * @param builder must not be {@literal null}.
+	 * @return empty {@code OrderSpecifier<?>[]} when sort is {@literal null}.
+	 */
+	public static OrderSpecifier<?>[] toOrderSpecifier(Sort sort, PathBuilder<?> builder) {
+
+		Assert.notNull(builder, "Builder must not be 'null'.");
+
+		if (sort == null) {
+			return new OrderSpecifier<?>[0];
+		}
+
+		List<OrderSpecifier<?>> specifiers = null;
+
+		if (sort instanceof QSort) {
+			specifiers = ((QSort) sort).getOrderSpecifiers();
+		} else {
+
+			specifiers = new ArrayList<OrderSpecifier<?>>();
+			for (Order order : sort) {
+				specifiers.add(toOrderSpecifier(order, builder));
+			}
+		}
+
+		return specifiers.toArray(new OrderSpecifier<?>[specifiers.size()]);
+	}
+
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	private static OrderSpecifier<?> toOrderSpecifier(Order order, PathBuilder<?> builder) {
+		return new OrderSpecifier(order.isAscending() ? com.mysema.query.types.Order.ASC
+				: com.mysema.query.types.Order.DESC, buildOrderPropertyPathFrom(order, builder),
+				toQueryDslNullHandling(order.getNullHandling()));
+	}
+
+	/**
+	 * Creates an {@link Expression} for the given {@link Order} property.
+	 * 
+	 * @param order must not be {@literal null}.
+	 * @param builder must not be {@literal null}.
+	 * @return
+	 */
+	private static Expression<?> buildOrderPropertyPathFrom(Order order, PathBuilder<?> builder) {
+
+		Assert.notNull(order, "Order must not be null!");
+		Assert.notNull(builder, "Builder must not be null!");
+
+		PropertyPath path = PropertyPath.from(order.getProperty(), builder.getType());
+		Expression<?> sortPropertyExpression = builder;
+
+		while (path != null) {
+
+			if (!path.hasNext() && order.isIgnoreCase()) {
+				// if order is ignore-case we have to treat the last path segment as a String.
+				sortPropertyExpression = Expressions.stringPath((Path<?>) sortPropertyExpression, path.getSegment()).lower();
+			} else {
+				sortPropertyExpression = Expressions.path(path.getType(), (Path<?>) sortPropertyExpression, path.getSegment());
+			}
+
+			path = path.next();
+		}
+
+		return sortPropertyExpression;
+	}
+
+	/**
+	 * Converts the given {@link org.springframework.data.domain.Sort.NullHandling} to the appropriate Querydsl
+	 * {@link NullHandling}.
+	 * 
+	 * @param nullHandling must not be {@literal null}.
+	 * @return
+	 */
+	private static NullHandling toQueryDslNullHandling(org.springframework.data.domain.Sort.NullHandling nullHandling) {
+
+		Assert.notNull(nullHandling, "NullHandling must not be null!");
+
+		switch (nullHandling) {
+
+			case NULLS_FIRST:
+				return NullHandling.NullsFirst;
+
+			case NULLS_LAST:
+				return NullHandling.NullsLast;
+
+			case NATIVE:
+			default:
+				return NullHandling.Default;
+		}
+	}
 }