DATACMNS-867 - Cleanups in Pageable API.

Dropped Pageable.NONE in favor of ….unpaged() for consistency with Sort.unsorted(). Extracted the implementation for the value backing it into an Unpaged enum instance. Introduced defaulted isPaged() / isUnpaged() to avoid having to compare instances.

JavaDoc in Sort and a couple of API polishes.

src/main/java/org/springframework/data/domain/Chunk.java

@@ -58,7 +58,7 @@ abstract class Chunk<T> implements Slice<T>, Serializable {
 	 * @see org.springframework.data.domain.Slice#getNumber()
 	 */
 	public int getNumber() {
-		return pageable == Pageable.NONE ? 0 : pageable.getPageNumber();
+		return pageable.isPaged() ? pageable.getPageNumber() : 0;
 	}
 
 	/*
@@ -66,7 +66,7 @@ abstract class Chunk<T> implements Slice<T>, Serializable {
 	 * @see org.springframework.data.domain.Slice#getSize()
 	 */
 	public int getSize() {
-		return pageable == Pageable.NONE ? 0 : pageable.getPageSize();
+		return pageable.isPaged() ? pageable.getPageSize() : 0;
 	}
 
 	/*
@@ -106,7 +106,7 @@ abstract class Chunk<T> implements Slice<T>, Serializable {
 	 * @see org.springframework.data.domain.Slice#nextPageable()
 	 */
 	public Pageable nextPageable() {
-		return hasNext() ? pageable.next() : Pageable.NONE;
+		return hasNext() ? pageable.next() : Pageable.unpaged();
 	}
 
 	/*
@@ -114,7 +114,7 @@ abstract class Chunk<T> implements Slice<T>, Serializable {
 	 * @see org.springframework.data.domain.Slice#previousPageable()
 	 */
 	public Pageable previousPageable() {
-		return hasPrevious() ? pageable.previousOrFirst() : Pageable.NONE;
+		return hasPrevious() ? pageable.previousOrFirst() : Pageable.unpaged();
 	}
 
 	/*

src/main/java/org/springframework/data/domain/PageImpl.java

@@ -47,7 +47,7 @@ public class PageImpl<T> extends Chunk<T> implements Page<T> {
 
 		this.pageable = pageable;
 
-		Optional<Pageable> foo = Pageable.NONE == pageable ? Optional.empty() : Optional.of(pageable);
+		Optional<Pageable> foo = pageable.isPaged() ? Optional.of(pageable) : Optional.empty();
 
 		this.total = foo.filter(it -> !content.isEmpty())//
 				.filter(it -> it.getOffset() + it.getPageSize() > total)//
@@ -62,7 +62,7 @@ public class PageImpl<T> extends Chunk<T> implements Page<T> {
 	 * @param content must not be {@literal null}.
 	 */
 	public PageImpl(List<T> content) {
-		this(content, Pageable.NONE, null == content ? 0 : content.size());
+		this(content, Pageable.unpaged(), null == content ? 0 : content.size());
 	}
 
 	/*

src/main/java/org/springframework/data/domain/Pageable.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.domain;
 
+import org.springframework.util.Assert;
+
 /**
  * Abstract interface for pagination information.
  * 
@@ -22,6 +24,33 @@ package org.springframework.data.domain;
  */
 public interface Pageable {
 
+	/**
+	 * Returns a {@link Pageable} instance representing no pagination setup.
+	 * 
+	 * @return
+	 */
+	static Pageable unpaged() {
+		return Unpaged.INSTANCE;
+	}
+
+	/**
+	 * Returns whether the current {@link Pageable} contains pagination information.
+	 * 
+	 * @return
+	 */
+	default boolean isPaged() {
+		return true;
+	}
+
+	/**
+	 * Returns whether the current {@link Pageable} does not contain pagination information.
+	 * 
+	 * @return
+	 */
+	default boolean isUnpaged() {
+		return !isPaged();
+	}
+
 	/**
 	 * Returns the page to be returned.
 	 * 
@@ -50,7 +79,16 @@ public interface Pageable {
 	 */
 	Sort getSort();
 
+	/**
+	 * Returns the current {@link Sort} or the given one if the current one is unsorted.
+	 * 
+	 * @param sort must not be {@literal null}.
+	 * @return
+	 */
 	default Sort getSortOr(Sort sort) {
+
+		Assert.notNull(sort, "Fallback Sort must not be null!");
+
 		return getSort().isSorted() ? getSort() : sort;
 	}
 
@@ -82,47 +120,4 @@ public interface Pageable {
 	 * @return
 	 */
 	boolean hasPrevious();
-
-	public static Pageable NONE = new Pageable() {
-
-		@Override
-		public Pageable previousOrFirst() {
-			return this;
-		}
-
-		@Override
-		public Pageable next() {
-			return this;
-		}
-
-		@Override
-		public boolean hasPrevious() {
-			return false;
-		}
-
-		@Override
-		public Sort getSort() {
-			return Sort.unsorted();
-		}
-
-		@Override
-		public int getPageSize() {
-			throw new UnsupportedOperationException();
-		}
-
-		@Override
-		public int getPageNumber() {
-			throw new UnsupportedOperationException();
-		}
-
-		@Override
-		public long getOffset() {
-			throw new UnsupportedOperationException();
-		}
-
-		@Override
-		public Pageable first() {
-			return this;
-		}
-	};
 }

src/main/java/org/springframework/data/domain/Sort.java

@@ -83,7 +83,7 @@ public class Sort implements Iterable<org.springframework.data.domain.Sort.Order
 	/**
 	 * Creates a new {@link Sort} instance.
 	 * 
-	 * @param direction defaults to {@linke Sort#DEFAULT_DIRECTION} (for {@literal null} cases, too)
+	 * @param direction defaults to {@link Sort#DEFAULT_DIRECTION} (for {@literal null} cases, too)
 	 * @param properties must not be {@literal null}, empty or contain {@literal null} or empty strings.
 	 */
 	public Sort(Direction direction, String... properties) {
@@ -109,38 +109,80 @@ public class Sort implements Iterable<org.springframework.data.domain.Sort.Order
 		}
 	}
 
+	/**
+	 * Creates a new {@link Sort} for the given properties.
+	 * 
+	 * @param properties must not be {@literal null}.
+	 * @return
+	 */
 	public static Sort by(String... properties) {
+
+		Assert.notNull(properties, "Properties must not be null!");
+
 		return properties.length == 0 ? Sort.unsorted() : new Sort(properties);
 	}
 
+	/**
+	 * Creates a new {@link Sort} for the given {@link Order}s.
+	 * 
+	 * @param orders must not be {@literal null}.
+	 * @return
+	 */
 	public static Sort by(List<Order> orders) {
+
+		Assert.notNull(orders, "Orders must not be null!");
+
 		return orders.isEmpty() ? Sort.unsorted() : new Sort(orders);
 	}
 
+	/**
+	 * Creates a new {@link Sort} for the given {@link Order}s.
+	 * 
+	 * @param orders must not be {@literal null}.
+	 * @return
+	 */
 	public static Sort by(Order... orders) {
+
+		Assert.notNull(orders, "Orders must not be null!");
+
 		return new Sort(orders);
 	}
 
+	/**
+	 * Returns a {@link Sort} instances representing no sorting setup at all.
+	 * 
+	 * @return
+	 */
 	public static Sort unsorted() {
 		return UNSORTED;
 	}
 
+	/**
+	 * Returns a new {@link Sort} with the current setup but descending order direction.
+	 * 
+	 * @return
+	 */
 	public Sort descending() {
 		return withDirection(Direction.DESC);
 	}
 
+	/**
+	 * Returns a new {@link Sort} with the current setup but ascendin order direction.
+	 * 
+	 * @return
+	 */
 	public Sort ascending() {
 		return withDirection(Direction.ASC);
 	}
 
-	private Sort withDirection(Direction direction) {
-		return new Sort(orders.stream().map(it -> new Order(direction, it.getProperty())).collect(Collectors.toList()));
-	}
-
 	public boolean isSorted() {
 		return !orders.isEmpty();
 	}
 
+	public boolean isUnorted() {
+		return !isSorted();
+	}
+
 	/**
 	 * Returns a new {@link Sort} consisting of the {@link Order}s of the current {@link Sort} combined with the given
 	 * ones.
@@ -160,7 +202,7 @@ public class Sort implements Iterable<org.springframework.data.domain.Sort.Order
 			these.add(order);
 		}
 
-		return new Sort(these);
+		return Sort.by(these);
 	}
 
 	/**
@@ -229,6 +271,17 @@ public class Sort implements Iterable<org.springframework.data.domain.Sort.Order
 		return orders.isEmpty() ? "UNSORTED" : StringUtils.collectionToCommaDelimitedString(orders);
 	}
 
+	/**
+	 * Creates a new {@link Sort} with the current setup but the given order direction.
+	 * 
+	 * @param direction
+	 * @return
+	 */
+	private Sort withDirection(Direction direction) {
+
+		return Sort.by(orders.stream().map(it -> new Order(direction, it.getProperty())).collect(Collectors.toList()));
+	}
+
 	/**
 	 * Enumeration for sort directions.
 	 * 

src/main/java/org/springframework/data/domain/Unpaged.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2017 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.domain;
+
+/**
+ * {@link Pageable} implementation to represent the absence of pagination information.
+ * 
+ * @author Oliver Gierke
+ */
+enum Unpaged implements Pageable {
+
+	INSTANCE;
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#isPaged()
+	 */
+	@Override
+	public boolean isPaged() {
+		return false;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#previousOrFirst()
+	 */
+	@Override
+	public Pageable previousOrFirst() {
+		return this;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#next()
+	 */
+	@Override
+	public Pageable next() {
+		return this;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#hasPrevious()
+	 */
+	@Override
+	public boolean hasPrevious() {
+		return false;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#getSort()
+	 */
+	@Override
+	public Sort getSort() {
+		return Sort.unsorted();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#getPageSize()
+	 */
+	@Override
+	public int getPageSize() {
+		throw new UnsupportedOperationException();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#getPageNumber()
+	 */
+	@Override
+	public int getPageNumber() {
+		throw new UnsupportedOperationException();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#getOffset()
+	 */
+	@Override
+	public long getOffset() {
+		throw new UnsupportedOperationException();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.domain.Pageable#first()
+	 */
+	@Override
+	public Pageable first() {
+		return this;
+	}
+}