加油，新时代打工人！

package com.love.starter.common.util;

import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import java.util.Map;

/**
 * 计算页开始及结束位置
 *
 * @author Administrator
 */
public class Page {
    public static final int PAGE_SIZE_TWENTY = 20;
    public static final int PAGE_SIZE_TEN = 10;
    public static final int PAGE_SIZE_TWELVE = 12;
    /**
     * 默认每页数量
     */
    private static final int DEFAULT_SIZE = 15;
    public static final int PAGE_SIZE_SEVEN = 7;
    public static final int PAGE_SIZE_FIFTY = 50;
    public static final int PAGE_SIZE_EIGHT = 8;
    public static final int PAGE_SIZE_FOURTEEN = 14;
    public static final int PAGE_SIZE_FIVE = 5;
    /**
     * 开始位置
     */
    private final int start;
    /**
     * 结束位置
     */
    private final int end;
    /**
     * 第几页
     */
    private int pageIndex = 1;
    /**
     * 每页记录数
     */
    private int pageSize = DEFAULT_SIZE;

    /**
     * 默认第一页，每页15行
     *
     * @param request
     */
    public Page(HttpServletRequest request) {
        String index = getPageIndex(request);
        String size = getPageSize(request);
        if (Nulls.isNotEmpty(index)) {
            pageIndex = Integer.parseInt(index);
        }
        if (Nulls.isNotEmpty(size)) {
            pageSize = Integer.parseInt(size);
        }
        start = (pageIndex - 1) * pageSize + 1;
        end = pageIndex * pageSize;
    }

    /**
     * @param request 请求
     * @param index   默认第几页
     * @param size    默认每页记录数量
     */
    public Page(HttpServletRequest request, int index, int size) {
        pageIndex = getPageIndex(request) == null ? index : Integer.parseInt(getPageIndex(request));
        pageSize = getPageSize(request) == null ? size : Integer.parseInt(getPageSize(request));
        start = (pageIndex - 1) * pageSize + 1;
        end = pageIndex * pageSize;
    }

    private static String getPageSize(HttpServletRequest request) {
        return request.getParameter("pageSize");
    }

    private static String getPageIndex(HttpServletRequest request) {
        return request.getParameter("pageIndex");
    }

    public void setQueryCondition(Map map) {
        map.put("START", start);
        map.put("END", end);
        map.put("start", start);
        map.put("end", end);
    }

    /**
     * 设置查询分页
     *
     * @param request
     * @param map
     */
    public static void setQueryByPage(HttpServletRequest request, Map map) {
        new Page(request).setQueryCondition(map);
    }

    /**
     * 在返回结果中增加页码
     *
     * @param mv
     */
    public void setReturnValue(ModelAndView mv) {
        mv.addObject("start", start);
    }

    /**
     * 设置查询尺寸
     *
     * @param map
     */
    public static void getSize(Map map) {
        int pageIndex = map.get("pageIndex") == null ? 1 : Integer.parseInt(map.get("pageIndex").toString());
        int pageSize = map.get("pageSize") == null ? DEFAULT_SIZE : Integer.parseInt(map.get("pageSize").toString());
        map.put("START", (pageIndex - 1) * pageSize);
        map.put("END", pageIndex * pageSize - 1);
    }

    public int getStart() {
        return this.start;
    }

    public int getEnd() {
        return this.end;
    }

    public int getPageIndex() {
        return this.pageIndex;
    }

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

    static class PageUtil {
        static void setPage(HttpServletRequest request, int pageSize, Map queryMap, ModelAndView mv) {
            Page page = new Page(request, 1, pageSize);
            page.setQueryCondition(queryMap);
            page.setReturnValue(mv);
        }
    }

}