org.mytms.common.data.Pageable.java Source code

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Here is the source code for org.mytms.common.data.Pageable.java

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/*
 * Copyright 2008-2017 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.mytms.common.data;

import org.springframework.util.Assert;

import java.util.Optional;

/**
 * Abstract interface for pagination information.
 * 
 * @author Oliver Gierke
 */
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.
     * 
     * @return the page to be returned.
     */
    int getPageNumber();

    /**
     * Returns the number of items to be returned.
     * 
     * @return the number of items of that page
     */
    int getPageSize();

    /**
     * Returns the offset to be taken according to the underlying page and page size.
     * 
     * @return the offset to be taken
     */
    long getOffset();

    /**
     * Returns the sorting parameters.
     * 
     * @return
     */
    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;
    }

    /**
     * Returns the {@link Pageable} requesting the next {@link Page}.
     * 
     * @return
     */
    Pageable next();

    /**
     * Returns the previous {@link Pageable} or the first {@link Pageable} if the current one already is the first one.
     * 
     * @return
     */
    Pageable previousOrFirst();

    /**
     * Returns the {@link Pageable} requesting the first page.
     * 
     * @return
     */
    Pageable first();

    /**
     * Returns whether there's a previous {@link Pageable} we can access from the current one. Will return
     * {@literal false} in case the current {@link Pageable} already refers to the first page.
     * 
     * @return
     */
    boolean hasPrevious();

    /**
     * Returns an {@link Optional} so that it can easily be mapped on.
     * 
     * @return
     */
    default Optional<Pageable> toOptional() {
        return isUnpaged() ? Optional.empty() : Optional.of(this);
    }
}