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The MyBatis SQL mapper framework makes it easier to use a relational database with object-oriented applications. MyBatis couples objects with stored procedures or SQL statements using a XML descriptor or annotations. Simplicity is the biggest advantage of the MyBatis data mapper over object relational mapping tools.

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/**
 *    Copyright 2009-2017 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.apache.ibatis.features.jpa.domain;

import java.util.List;

public class PageImpl extends Chunk implements Page {

	private static final long serialVersionUID = 867755909294344406L;

	private final long total;
	private final Pageable pageable;

	/**
	 * Constructor of {@code PageImpl}.
	 * 
	 * @param content the content of this page, must not be {@literal null}.
	 * @param pageable the paging information, can be {@literal null}.
	 * @param total the total amount of items available. The total might be adapted considering the length of the content
	 *          given, if it is going to be the content of the last page. This is in place to mitigate inconsistencies
	 */
	public PageImpl(List content, Pageable pageable, long total) {

		super(content, pageable);

		this.pageable = pageable;
		this.total = pageable.toOptional().filter(it -> !content.isEmpty())//
				.filter(it -> it.getOffset() + it.getPageSize() > total)//
				.map(it -> it.getOffset() + content.size())//
				.orElse(total);
	}

	/**
	 * Creates a new {@link PageImpl} with the given content. This will result in the created {@link Page} being identical
	 * to the entire {@link List}.
	 * 
	 * @param content must not be {@literal null}.
	 */
	public PageImpl(List content) {
		this(content, Pageable.unpaged(), null == content ? 0 : content.size());
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Page#getTotalPages()
	 */
	@Override
	public int getTotalPages() {
		return getSize() == 0 ? 1 : (int) Math.ceil((double) total / (double) getSize());
	}

	/*
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Page#getTotalElements()
	 */
	@Override
	public long getTotalElements() {
		return total;
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Slice#hasNext()
	 */
	@Override
	public boolean hasNext() {
		return getNumber() + 1 < getTotalPages();
	}

	/* 
	 * (non-Javadoc)
	 * @see org.springframework.data.domain.Slice#isLast()
	 */
	@Override
	public boolean isLast() {
		return !hasNext();
	}

	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {

		String contentType = "UNKNOWN";
		List content = getContent();

		if (content.size() > 0) {
			contentType = content.get(0).getClass().getName();
		}

		return String.format("Page %s of %d containing %s instances", getNumber() + 1, getTotalPages(), contentType);
	}

	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#equals(java.lang.Object)
	 */
	@Override
	public boolean equals(Object obj) {

		if (this == obj) {
			return true;
		}

		if (!(obj instanceof PageImpl)) {
			return false;
		}

		PageImpl that = (PageImpl) obj;

		return this.total == that.total && super.equals(obj);
	}

	/*
	 * (non-Javadoc)
	 * @see java.lang.Object#hashCode()
	 */
	@Override
	public int hashCode() {

		int result = 17;

		result += 31 * (int) (total ^ total >>> 32);
		result += 31 * super.hashCode();

		return result;
	}
}