spring boot學習 ---- 使用pageHelper實現分頁功能

目錄

　　1.介紹pageHelper

　　2.pageHelper的基本配置

　　3.使用pageHelper實現分頁功能

一、介紹pageHelper

　　pageHelper是一款分頁插件，它能很好的集成在spring boot中在它是一個基於mybatis的一款插件。它是的底層實現技術則是使用動態代理實現的。所以我們在使用它時，我們需要使用mybatis作為持久層框架。如果有需要請參照《spring boot 集成 mybatis》

二、pageHelper的基本配置

　　如果我們需要使用pageHelper的話，我們需要在spring boot項目中引入pageHelper的依賴。以下是PageHelper的GitHub地址https://github.com/pagehelper/Mybatis-PageHelper

　　在這里我們導入以下依賴：

<!-- pagehelper -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
            <version>1.2.5</version>
        </dependency>

　　同樣，我們在spring boot的application.properties中可以配置pageHelper的基本信息，

# 指定數據庫，不指定的話會默認自動檢測數據庫類型
pagehelper.helperDialect=mysql
# 是否啟用分頁合理化。
# 如果啟用，當pagenum<1時，會自動查詢第一頁的數據，當pagenum>pages時，自動查詢最后一頁數據；
# 不啟用的，以上兩種情況都會返回空數據
pagehelper.reasonable=true
# 默認值false，分頁插件會從查詢方法的參數值中，自動根據上面 params 配置的字段中取值，查找到合適的值時就會自動分頁。
pagehelper.supportMethodsArguments=true
# 用於從對象中根據屬性名取值，
# 可以配置 pageNum,pageSize,count,pageSizeZero,reasonable，不配置映射的用默認值，
# 默認值為pageNum=pageNum;pageSize=pageSize;count=countSql;reasonable=reasonable;pageSizeZero=pageSizeZero
pagehelper.params=count=countSql

　　在1.2.5這個版本中我們可以不用配置，使用默認的就夠用了。

三、使用pageHelper實現分頁功能

　　在上一步中，我們已近知道pageHelper的基本配置了。在這，我們使用pageHelper實現分頁功能。

我們使用《mysql必知必會》中給出的數據庫進行分頁查詢。

　　1.創建City實體類

package com.springboot.pagehelper;

public class City {
//    id
    private int id;
//    國家名
    private String name;
//    國家代碼
    private String countryCode;
//    地區
    private String district;
//    人口
    private int population;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getCountryCode() {
        return countryCode;
    }

    public void setCountryCode(String countryCode) {
        this.countryCode = countryCode;
    }

    public String getDistrict() {
        return district;
    }

    public void setDistrict(String district) {
        this.district = district;
    }

    public int getPopulation() {
        return population;
    }

    public void setPopulation(int population) {
        this.population = population;
    }
}

　　2.數據操作層查詢出所有數據

package com.springboot.pagehelper.mapper;

import com.springboot.pagehelper.City;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Repository;

import java.util.List;

@Mapper
@Repository
public interface CityMapper {
//    獲取所有城市
    @Select("select * from city")
    @Results({
            @Result(property = "id",column = "ID"),
            @Result(property = "name",column = "Name"),
            @Result(property = "countryCode",column = "CountryCode"),
            @Result(property = "district",column = "District"),
            @Result(property = "population",column = "Population")
    })
    List<City> selectCity();
}

　　3.創建業務接口

　　這里我們使用兩種實現

package com.springboot.pagehelper.service;

import com.github.pagehelper.Page;
import com.springboot.pagehelper.City;

import java.util.List;

public interface CityService {
    List<City> getcity();
    Page<City> pageCity();
}

　　4.實現業務接口

package com.springboot.pagehelper.service;

import com.github.pagehelper.Page;
import com.springboot.pagehelper.City;
import com.springboot.pagehelper.mapper.CityMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class CityServiceImpl implements  CityService {

    @Autowired
    private CityMapper mapper;

    @Override
    public List<City> getcity() {
        return mapper.selectCity();
    }

    @Override
    public Page<City> pageCity() {
        return (Page<City>)mapper.selectCity();
    }
}

　　5.控制層實現分頁

package com.springboot.pagehelper.controller;

import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import com.springboot.pagehelper.City;
import com.springboot.pagehelper.service.CityService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
public class DataController {
    @Autowired
    private CityService service;
    @GetMapping("/citys/{page}")
    public PageInfo<City> lists(@PathVariable int page){
//        設置分頁規則
        PageHelper.startPage(page,10);
//        返回所有分頁信息參數為查詢所有記錄的信息
        PageInfo<City> pageInfo = new PageInfo<>(service.pageCity());
        return pageInfo;
    }

    @GetMapping("/city")
    public List<City> paraList(@RequestParam(defaultValue = "1") int p,
                               @RequestParam(defaultValue = "10") int size){
//        設置分頁規則
        PageHelper.startPage(p,size);
//        取數據，插件會自動按照規則分頁顯示數據
        return service.getcity();
    }
}

　　實現分頁功能在使用時，PageInfo源碼如下：

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2014-2017 [e-mail]
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package com.github.pagehelper;

import java.io.Serializable;
import java.util.Collection;
import java.util.List;

/**
 * 對Page<E>結果進行包裝
 * <p/>
 * 新增分頁的多項屬性，主要參考:http://bbs.csdn.net/topics/360010907
 *
 * @author liuzh/abel533/isea533
 * @version 3.3.0
 * @since 3.2.2
 * 項目地址 : http://git.oschina.net/free/Mybatis_PageHelper
 */
@SuppressWarnings({"rawtypes", "unchecked"})
public class PageInfo<T> extends PageSerializable<T> {
    //當前頁
    private int pageNum;
    //每頁的數量
    private int pageSize;
    //當前頁的數量
    private int size;

    //由於startRow和endRow不常用，這里說個具體的用法
    //可以在頁面中"顯示startRow到endRow 共size條數據"

    //當前頁面第一個元素在數據庫中的行號
    private int startRow;
    //當前頁面最后一個元素在數據庫中的行號
    private int endRow;
    //總頁數
    private int pages;

    //前一頁
    private int prePage;
    //下一頁
    private int nextPage;

    //是否為第一頁
    private boolean isFirstPage = false;
    //是否為最后一頁
    private boolean isLastPage = false;
    //是否有前一頁
    private boolean hasPreviousPage = false;
    //是否有下一頁
    private boolean hasNextPage = false;
    //導航頁碼數
    private int navigatePages;
    //所有導航頁號
    private int[] navigatepageNums;
    //導航條上的第一頁
    private int navigateFirstPage;
    //導航條上的最后一頁
    private int navigateLastPage;

    public PageInfo() {
    }

    /**
     * 包裝Page對象
     *
     * @param list
     */
    public PageInfo(List<T> list) {
        this(list, 8);
    }

    /**
     * 包裝Page對象
     *
     * @param list          page結果
     * @param navigatePages 頁碼數量
     */
    public PageInfo(List<T> list, int navigatePages) {
        super(list);
        if (list instanceof Page) {
            Page page = (Page) list;
            this.pageNum = page.getPageNum();
            this.pageSize = page.getPageSize();

            this.pages = page.getPages();
            this.size = page.size();
            //由於結果是>startRow的，所以實際的需要+1
            if (this.size == 0) {
                this.startRow = 0;
                this.endRow = 0;
            } else {
                this.startRow = page.getStartRow() + 1;
                //計算實際的endRow（最后一頁的時候特殊）
                this.endRow = this.startRow - 1 + this.size;
            }
        } else if (list instanceof Collection) {
            this.pageNum = 1;
            this.pageSize = list.size();

            this.pages = this.pageSize > 0 ? 1 : 0;
            this.size = list.size();
            this.startRow = 0;
            this.endRow = list.size() > 0 ? list.size() - 1 : 0;
        }
        if (list instanceof Collection) {
            this.navigatePages = navigatePages;
            //計算導航頁
            calcNavigatepageNums();
            //計算前后頁，第一頁，最后一頁
            calcPage();
            //判斷頁面邊界
            judgePageBoudary();
        }
    }

    public static <T> PageInfo<T> of(List<T> list){
        return new PageInfo<T>(list);
    }

    public static <T> PageInfo<T> of(List<T> list, int navigatePages){
        return new PageInfo<T>(list, navigatePages);
    }

    /**
     * 計算導航頁
     */
    private void calcNavigatepageNums() {
        //當總頁數小於或等於導航頁碼數時
        if (pages <= navigatePages) {
            navigatepageNums = new int[pages];
            for (int i = 0; i < pages; i++) {
                navigatepageNums[i] = i + 1;
            }
        } else { //當總頁數大於導航頁碼數時
            navigatepageNums = new int[navigatePages];
            int startNum = pageNum - navigatePages / 2;
            int endNum = pageNum + navigatePages / 2;

            if (startNum < 1) {
                startNum = 1;
                //(最前navigatePages頁
                for (int i = 0; i < navigatePages; i++) {
                    navigatepageNums[i] = startNum++;
                }
            } else if (endNum > pages) {
                endNum = pages;
                //最后navigatePages頁
                for (int i = navigatePages - 1; i >= 0; i--) {
                    navigatepageNums[i] = endNum--;
                }
            } else {
                //所有中間頁
                for (int i = 0; i < navigatePages; i++) {
                    navigatepageNums[i] = startNum++;
                }
            }
        }
    }

    /**
     * 計算前后頁，第一頁，最后一頁
     */
    private void calcPage() {
        if (navigatepageNums != null && navigatepageNums.length > 0) {
            navigateFirstPage = navigatepageNums[0];
            navigateLastPage = navigatepageNums[navigatepageNums.length - 1];
            if (pageNum > 1) {
                prePage = pageNum - 1;
            }
            if (pageNum < pages) {
                nextPage = pageNum + 1;
            }
        }
    }

    /**
     * 判定頁面邊界
     */
    private void judgePageBoudary() {
        isFirstPage = pageNum == 1;
        isLastPage = pageNum == pages || pages == 0;;
        hasPreviousPage = pageNum > 1;
        hasNextPage = pageNum < pages;
    }

    public int getPageNum() {
        return pageNum;
    }

    public void setPageNum(int pageNum) {
        this.pageNum = pageNum;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getSize() {
        return size;
    }

    public void setSize(int size) {
        this.size = size;
    }

    public int getStartRow() {
        return startRow;
    }

    public void setStartRow(int startRow) {
        this.startRow = startRow;
    }

    public int getEndRow() {
        return endRow;
    }

    public void setEndRow(int endRow) {
        this.endRow = endRow;
    }

    public int getPages() {
        return pages;
    }

    public void setPages(int pages) {
        this.pages = pages;
    }

    @Deprecated
    // firstPage就是1, 此函數獲取的是導航條上的第一頁, 容易產生歧義
    public int getFirstPage() {
        return navigateFirstPage;
    }

    @Deprecated
    public void setFirstPage(int firstPage) {
        this.navigateFirstPage = firstPage;
    }

    public int getPrePage() {
        return prePage;
    }

    public void setPrePage(int prePage) {
        this.prePage = prePage;
    }

    public int getNextPage() {
        return nextPage;
    }

    public void setNextPage(int nextPage) {
        this.nextPage = nextPage;
    }

    @Deprecated
    // 請用getPages()來獲取最后一頁, 此函數獲取的是導航條上的最后一頁, 容易產生歧義.
    public int getLastPage() {
        return navigateLastPage;
    }

    @Deprecated
    public void setLastPage(int lastPage) {
        this.navigateLastPage = lastPage;
    }

    public boolean isIsFirstPage() {
        return isFirstPage;
    }

    public void setIsFirstPage(boolean isFirstPage) {
        this.isFirstPage = isFirstPage;
    }

    public boolean isIsLastPage() {
        return isLastPage;
    }

    public void setIsLastPage(boolean isLastPage) {
        this.isLastPage = isLastPage;
    }

    public boolean isHasPreviousPage() {
        return hasPreviousPage;
    }

    public void setHasPreviousPage(boolean hasPreviousPage) {
        this.hasPreviousPage = hasPreviousPage;
    }

    public boolean isHasNextPage() {
        return hasNextPage;
    }

    public void setHasNextPage(boolean hasNextPage) {
        this.hasNextPage = hasNextPage;
    }

    public int getNavigatePages() {
        return navigatePages;
    }

    public void setNavigatePages(int navigatePages) {
        this.navigatePages = navigatePages;
    }

    public int[] getNavigatepageNums() {
        return navigatepageNums;
    }

    public void setNavigatepageNums(int[] navigatepageNums) {
        this.navigatepageNums = navigatepageNums;
    }

    public int getNavigateFirstPage() {
        return navigateFirstPage;
    }

    public int getNavigateLastPage() {
        return navigateLastPage;
    }

    public void setNavigateFirstPage(int navigateFirstPage) {
        this.navigateFirstPage = navigateFirstPage;
    }

    public void setNavigateLastPage(int navigateLastPage) {
        this.navigateLastPage = navigateLastPage;
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder("PageInfo{");
        sb.append("pageNum=").append(pageNum);
        sb.append(", pageSize=").append(pageSize);
        sb.append(", size=").append(size);
        sb.append(", startRow=").append(startRow);
        sb.append(", endRow=").append(endRow);
        sb.append(", total=").append(total);
        sb.append(", pages=").append(pages);
        sb.append(", list=").append(list);
        sb.append(", prePage=").append(prePage);
        sb.append(", nextPage=").append(nextPage);
        sb.append(", isFirstPage=").append(isFirstPage);
        sb.append(", isLastPage=").append(isLastPage);
        sb.append(", hasPreviousPage=").append(hasPreviousPage);
        sb.append(", hasNextPage=").append(hasNextPage);
        sb.append(", navigatePages=").append(navigatePages);
        sb.append(", navigateFirstPage=").append(navigateFirstPage);
        sb.append(", navigateLastPage=").append(navigateLastPage);
        sb.append(", navigatepageNums=");
        if (navigatepageNums == null) {
            sb.append("null");
        } else {
            sb.append('[');
            for (int i = 0; i < navigatepageNums.length; ++i) {
                sb.append(i == 0 ? "" : ", ").append(navigatepageNums[i]);
            }
            sb.append(']');
        }
        sb.append('}');
        return sb.toString();
    }
}

　　它包括了許多分頁信息，我們可以獲取所有分頁信息，發到前端，最后渲染到頁面上。

　　之后我們可以通過瀏覽器來獲取到我們的數據了。

第一個版本（傳參方式）：

 

第二個版本（改變地址欄）：

　　 到這就完成了分頁的功能。