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the hasor DataBase project.
There is a newer version: 4.3.5
/*
 * Copyright 2002-2005 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 net.hasor.db.jdbc.page;
import net.hasor.utils.function.ESupplier;

import java.sql.SQLException;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * 分页接口 Page 的实现类
 * @version : 2021-02-04
 * @author 赵永春 ([email protected])
 */
public class PageObject implements Page {
    /** 满足条件的总记录数 */
    private       ESupplier totalCountSupplier = () -> 0;
    private       int                              totalCount         = 0;
    private final AtomicBoolean                    totalCountInited   = new AtomicBoolean(false);
    /** 每页记录数（-1表示无限大）*/
    private       int                              pageSize           = 0;
    /** 当前页号 */
    private       int                              currentPage        = 0;
    /** 起始页码的偏移量 */
    private       int                              pageNumberOffset   = 0;

    public PageObject() {
        this.totalCountSupplier = () -> 0;
    }

    public PageObject(int pageSize, ESupplier totalCountSupplier) {
        Objects.requireNonNull(totalCountSupplier, "totalCountSupplier is null.");
        this.pageSize = pageSize;
        this.totalCountSupplier = totalCountSupplier;
    }

    public int getPageSize() {
        return this.pageSize;
    }

    /** 设置分页的页大小 */
    public void setPageSize(int pageSize) {
        if (pageSize <= 0) {
            this.pageSize = 0;
        } else {
            this.pageSize = pageSize;
        }
    }

    /**取当前页号 */
    public int getCurrentPage() {
        if (this.pageSize > 0) {
            return this.currentPage + this.pageNumberOffset;
        } else {
            return this.pageNumberOffset;
        }
    }

    /** 设置前页号 */
    public void setCurrentPage(int currentPage) {
        if (currentPage <= this.pageNumberOffset) {
            this.currentPage = 0;
        } else {
            this.currentPage = currentPage - this.pageNumberOffset;
        }
    }

    public int getPageNumberOffset() {
        return this.pageNumberOffset;
    }

    public void setPageNumberOffset(int pageNumberOffset) {
        this.pageNumberOffset = Math.max(pageNumberOffset, 0);
    }

    /** 获取本页第一个记录的索引位置 */
    public int getFirstRecordPosition() {
        int pgSize = getPageSize();
        if (pgSize <= 0) {
            return 0;
        }
        return pgSize * this.currentPage;
    }

    /** 获取总页数 */
    public int getTotalPage() throws SQLException {
        int pgSize = getPageSize();
        if (pgSize > 0) {
            int totalCount = getTotalCount();
            if (totalCount == 0) {
                return this.pageNumberOffset;
            }
            int result = totalCount / pgSize;
            if ((totalCount % pgSize) != 0) {
                result++;
            }
            return result + this.pageNumberOffset;
        } else {
            int totalCount = getTotalCount();
            if (totalCount > 0) {
                return this.pageNumberOffset + 1;
            } else {
                return this.pageNumberOffset;
            }
        }
    }

    /** 获取记录总数 */
    public int getTotalCount() throws SQLException {
        if (this.totalCountInited.compareAndSet(false, true)) {
            this.totalCount = this.totalCountSupplier.eGet();
        }
        return this.totalCount;
    }
}