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  • spring boot学习 ---- 使用pageHelper实现分页功能

    目录

      1.介绍pageHelper

      2.pageHelper的基本配置

      3.使用pageHelper实现分页功能

    一、介绍pageHelper

      pageHelper是一款分页插件,它能很好的集成在spring boot中在它是一个基于mybatis的一款插件。它是的底层实现技术则是使用动态代理实现的。所以我们在使用它时,我们需要使用mybatis作为持久层框架。如果有需要请参照《spring boot 集成 mybatis》

    二、pageHelper的基本配置

      如果我们需要使用pageHelper的话,我们需要在spring boot项目中引入pageHelper的依赖。以下是PageHelper的GitHub地址https://github.com/pagehelper/Mybatis-PageHelper

      在这里我们导入以下依赖:

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

      同样,我们在spring boot的application.properties中可以配置pageHelper的基本信息,

    # 指定数据库,不指定的话会默认自动检测数据库类型
    pagehelper.helperDialect=mysql
    # 是否启用分页合理化。
    # 如果启用,当pagenum<1时,会自动查询第一页的数据,当pagenum>pages时,自动查询最后一页数据;
    # 不启用的,以上两种情况都会返回空数据
    pagehelper.reasonable=true
    # 默认值false,分页插件会从查询方法的参数值中,自动根据上面 params 配置的字段中取值,查找到合适的值时就会自动分页。
    pagehelper.supportMethodsArguments=true
    # 用于从对象中根据属性名取值,
    # 可以配置 pageNum,pageSize,count,pageSizeZero,reasonable,不配置映射的用默认值,
    # 默认值为pageNum=pageNum;pageSize=pageSize;count=countSql;reasonable=reasonable;pageSizeZero=pageSizeZero
    pagehelper.params=count=countSql

      在1.2.5这个版本中我们可以不用配置,使用默认的就够用了。

    三、使用pageHelper实现分页功能

      在上一步中,我们已近知道pageHelper的基本配置了。在这,我们使用pageHelper实现分页功能。

    我们使用《mysql必知必会》中给出的数据库进行分页查询。

      1.创建City实体类

    package com.springboot.pagehelper;
    
    public class City {
    //    id
        private int id;
    //    国家名
        private String name;
    //    国家代码
        private String countryCode;
    //    地区
        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;
        }
    }
    City

      2.数据操作层查询出所有数据

    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 {
    //    获取所有城市
        @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();
    }
    CityMapper

      3.创建业务接口

      这里我们使用两种实现

    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();
    }
    CityService

      4.实现业务接口

    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();
        }
    }
    CityServiceImpl

      5.控制层实现分页

    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){
    //        设置分页规则
            PageHelper.startPage(page,10);
    //        返回所有分页信息参数为查询所有记录的信息
            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){
    //        设置分页规则
            PageHelper.startPage(p,size);
    //        取数据,插件会自动按照规则分页显示数据
            return service.getcity();
        }
    }
    DataController

      实现分页功能在使用时,PageInfo源码如下:

    /*
     * The MIT License (MIT)
     *
     * Copyright (c) 2014-2017 abel533@gmail.com
     *
     * 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;
    
    /**
     * 对Page<E>结果进行包装
     * <p/>
     * 新增分页的多项属性,主要参考:http://bbs.csdn.net/topics/360010907
     *
     * @author liuzh/abel533/isea533
     * @version 3.3.0
     * @since 3.2.2
     * 项目地址 : http://git.oschina.net/free/Mybatis_PageHelper
     */
    @SuppressWarnings({"rawtypes", "unchecked"})
    public class PageInfo<T> extends PageSerializable<T> {
        //当前页
        private int pageNum;
        //每页的数量
        private int pageSize;
        //当前页的数量
        private int size;
    
        //由于startRow和endRow不常用,这里说个具体的用法
        //可以在页面中"显示startRow到endRow 共size条数据"
    
        //当前页面第一个元素在数据库中的行号
        private int startRow;
        //当前页面最后一个元素在数据库中的行号
        private int endRow;
        //总页数
        private int pages;
    
        //前一页
        private int prePage;
        //下一页
        private int nextPage;
    
        //是否为第一页
        private boolean isFirstPage = false;
        //是否为最后一页
        private boolean isLastPage = false;
        //是否有前一页
        private boolean hasPreviousPage = false;
        //是否有下一页
        private boolean hasNextPage = false;
        //导航页码数
        private int navigatePages;
        //所有导航页号
        private int[] navigatepageNums;
        //导航条上的第一页
        private int navigateFirstPage;
        //导航条上的最后一页
        private int navigateLastPage;
    
        public PageInfo() {
        }
    
        /**
         * 包装Page对象
         *
         * @param list
         */
        public PageInfo(List<T> list) {
            this(list, 8);
        }
    
        /**
         * 包装Page对象
         *
         * @param list          page结果
         * @param navigatePages 页码数量
         */
        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();
                //由于结果是>startRow的,所以实际的需要+1
                if (this.size == 0) {
                    this.startRow = 0;
                    this.endRow = 0;
                } else {
                    this.startRow = page.getStartRow() + 1;
                    //计算实际的endRow(最后一页的时候特殊)
                    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;
                //计算导航页
                calcNavigatepageNums();
                //计算前后页,第一页,最后一页
                calcPage();
                //判断页面边界
                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);
        }
    
        /**
         * 计算导航页
         */
        private void calcNavigatepageNums() {
            //当总页数小于或等于导航页码数时
            if (pages <= navigatePages) {
                navigatepageNums = new int[pages];
                for (int i = 0; i < pages; i++) {
                    navigatepageNums[i] = i + 1;
                }
            } else { //当总页数大于导航页码数时
                navigatepageNums = new int[navigatePages];
                int startNum = pageNum - navigatePages / 2;
                int endNum = pageNum + navigatePages / 2;
    
                if (startNum < 1) {
                    startNum = 1;
                    //(最前navigatePages页
                    for (int i = 0; i < navigatePages; i++) {
                        navigatepageNums[i] = startNum++;
                    }
                } else if (endNum > pages) {
                    endNum = pages;
                    //最后navigatePages页
                    for (int i = navigatePages - 1; i >= 0; i--) {
                        navigatepageNums[i] = endNum--;
                    }
                } else {
                    //所有中间页
                    for (int i = 0; i < navigatePages; i++) {
                        navigatepageNums[i] = startNum++;
                    }
                }
            }
        }
    
        /**
         * 计算前后页,第一页,最后一页
         */
        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;
                }
            }
        }
    
        /**
         * 判定页面边界
         */
        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, 此函数获取的是导航条上的第一页, 容易产生歧义
        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
        // 请用getPages()来获取最后一页, 此函数获取的是导航条上的最后一页, 容易产生歧义.
        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();
        }
    }
    PageInfo

      它包括了许多分页信息,我们可以获取所有分页信息,发到前端,最后渲染到页面上。

      之后我们可以通过浏览器来获取到我们的数据了。

    第一个版本(传参方式):

    第二个版本(改变地址栏):

       到这就完成了分页的功能。

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  • 原文地址:https://www.cnblogs.com/bananafish/p/10481798.html
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