若依startPage()详解

背景

startPage基于PageHelper来进行强化，在用户传入pagesize,pageNum等标准参数的时候不需要进行解析

步骤

1.通过ServletUtils工具类getRequestAttributes来获取当前线程的上下文信息

public static ServletRequestAttributes getRequestAttributes() {
        try {
            RequestAttributes attributes = RequestContextHolder.getRequestAttributes();
            return (ServletRequestAttributes)attributes;
        } catch (Exception var1) {
            return null;
        }
    }

2. 通过getRequest方法来获取本次的HttpServletRequest请求

public static HttpServletRequest getRequest() {
        try {
            return getRequestAttributes().getRequest();
        } catch (Exception var1) {
            return null;
        }
    }

3. 通过getParameter方法来获取本次request的请求参数

public static String getParameter(String name) {
        return getRequest().getParameter(name);
    }

4. 在getPageDomain方法中，通过ServletUtils.getParameter方法获取到具体参数，若没有就使用默认值

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package com.lml.common.core.web.page;

import com.lml.common.core.text.Convert;
import com.lml.common.core.utils.ServletUtils;

public class TableSupport {
    public static final String PAGE_NUM = "pageNum";
    public static final String PAGE_SIZE = "pageSize";
    public static final String ORDER_BY_COLUMN = "orderByColumn";
    public static final String IS_ASC = "isAsc";
    public static final String REASONABLE = "reasonable";

    public TableSupport() {
    }

    public static PageDomain getPageDomain() {
        PageDomain pageDomain = new PageDomain();
        pageDomain.setPageNum(Convert.toInt(ServletUtils.getParameter("pageNum"), 1));
        pageDomain.setPageSize(Convert.toInt(ServletUtils.getParameter("pageSize"), 10));
        pageDomain.setOrderByColumn(ServletUtils.getParameter("orderByColumn"));
        pageDomain.setIsAsc(ServletUtils.getParameter("isAsc"));
        pageDomain.setReasonable(ServletUtils.getParameterToBool("reasonable"));
        return pageDomain;
    }

    public static PageDomain buildPageRequest() {
        return getPageDomain();
    }
}

5. 通过调用PageUtils.startPage方法来代替重复的PageHelper.startPage赋值

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package com.lml.common.core.utils;

import com.github.pagehelper.PageHelper;
import com.lml.common.core.utils.sql.SqlUtil;
import com.lml.common.core.web.page.PageDomain;
import com.lml.common.core.web.page.TableSupport;

public class PageUtils extends PageHelper {
    public PageUtils() {
    }

    public static void startPage() {
        PageDomain pageDomain = TableSupport.buildPageRequest();
        Integer pageNum = pageDomain.getPageNum();
        Integer pageSize = pageDomain.getPageSize();
        String orderBy = SqlUtil.escapeOrderBySql(pageDomain.getOrderBy());
        Boolean reasonable = pageDomain.getReasonable();
        PageHelper.startPage(pageNum, pageSize, orderBy).setReasonable(reasonable);
    }

    public static void clearPage() {
        PageHelper.clearPage();
    }
}

6. 控制台层通过继承BaseController，然后调用startPage()方法来进行翻页

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package com.lml.common.core.web.controller;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.lml.common.core.utils.DateUtils;
import com.lml.common.core.utils.PageUtils;
import com.lml.common.core.utils.StringUtils;
import com.lml.common.core.utils.sql.SqlUtil;
import com.lml.common.core.web.domain.AjaxResult;
import com.lml.common.core.web.page.PageDomain;
import com.lml.common.core.web.page.TableDataInfo;
import com.lml.common.core.web.page.TableSupport;
import java.beans.PropertyEditorSupport;
import java.util.Date;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.InitBinder;

public class BaseController {
    protected final Logger logger = LoggerFactory.getLogger(this.getClass());

    public BaseController() {
    }

    @InitBinder
    public void initBinder(WebDataBinder binder) {
        binder.registerCustomEditor(Date.class, new PropertyEditorSupport() {
            public void setAsText(String text) {
                this.setValue(DateUtils.parseDate(text));
            }
        });
    }

    protected void startPage() {
        PageUtils.startPage();
    }

    protected void startOrderBy() {
        PageDomain pageDomain = TableSupport.buildPageRequest();
        if (StringUtils.isNotEmpty(pageDomain.getOrderBy())) {
            String orderBy = SqlUtil.escapeOrderBySql(pageDomain.getOrderBy());
            PageHelper.orderBy(orderBy);
        }

    }

    protected void clearPage() {
        PageUtils.clearPage();
    }

    protected TableDataInfo getDataTable(List<?> list) {
        TableDataInfo rspData = new TableDataInfo();
        rspData.setCode(200);
        rspData.setRows(list);
        rspData.setMsg("查询成功");
        rspData.setTotal((new PageInfo(list)).getTotal());
        return rspData;
    }

    public AjaxResult success() {
        return AjaxResult.success();
    }

    public AjaxResult success(String message) {
        return AjaxResult.success(message);
    }

    public AjaxResult success(Object data) {
        return AjaxResult.success(data);
    }

    public AjaxResult error() {
        return AjaxResult.error();
    }

    public AjaxResult error(String message) {
        return AjaxResult.error(message);
    }

    public AjaxResult warn(String message) {
        return AjaxResult.warn(message);
    }

    protected AjaxResult toAjax(int rows) {
        return rows > 0 ? AjaxResult.success() : AjaxResult.error();
    }

    protected AjaxResult toAjax(boolean result) {
        return result ? this.success() : this.error();
    }
}