一文彻底搞懂Mybatis系列（十七）之MyBatis使用分页插件PageHelper

小咪咪 2024-04-01 12:38 48阅读 0赞

**往期文章：**  
[一文彻底搞懂Mybatis系列（一）之mybatis入门][Mybatis_mybatis]  
[一文彻底搞懂Mybatis系列（二）之mybatis事务管理机制深度剖析][Mybatis_mybatis 1]  
[一文彻底搞懂Mybatis系列（三）之mybatis完成增删改查CURD功能超级详细][Mybatis_mybatis_CURD]  
[一文彻底搞懂Mybatis系列（四）之mybatis核心配置文件详解][Mybatis_mybatis 2]  
[一文彻底搞懂Mybatis系列（五）之手写Mybatis框架简单探索版][Mybatis_Mybatis]  
[一文彻底搞懂Mybatis系列（六）之在WEB应用中使用Mybatis][Mybatis_WEB_Mybatis]  
[一文彻底搞懂Mybatis系列（七）之使用Mybatis的小技巧][Mybatis_Mybatis 1]  
[一文彻底搞懂Mybatis系列（八）之Mybatis参数处理][Mybatis_Mybatis 2]  
[一文彻底搞懂Mybatis系列（九）之Mybatis动态SQL标签总结][Mybatis_Mybatis_SQL]  
[一文彻底搞懂Mybatis系列（十）之SqlSession、SqlSessionFactory和SqlSessionFactoryBuilder详解][Mybatis_SqlSession_SqlSessionFactory_SqlSessionFactoryBuilder]  
[一文彻底搞懂Mybatis系列（十一）之MyBatis多对一映射查询][Mybatis_MyBatis]  
[一文彻底搞懂Mybatis系列（十二）之MyBatis多对一映射延迟加载（association和lazyLoadingEnabled）][Mybatis_MyBatis_association_lazyLoadingEnabled]  
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[一文彻底搞懂Mybatis系列（十四）之MyBatis一级缓存][Mybatis_MyBatis 2]  
[一文彻底搞懂Mybatis系列（十五）之MyBatis二级缓存][Mybatis_MyBatis 3]  
[一文彻底搞懂Mybatis系列（十六）之MyBatis集成EhCache][Mybatis_MyBatis_EhCache]  
[一文彻底搞懂Mybatis系列（十七）之MyBatis使用分页插件PageHelper][Mybatis_MyBatis_PageHelper]

## 一、关于mysql的分页说明 ##

**1、mysql当中的分页sql需要使用limit关键字。**

**2、limit 语法格式:**

limit startIndex,pageSize  
startIndex ：开始下标  
pageSize：显示的记录条数

select \* from t car limit 0, 3;  
mysql当中起始行的下标从0开始。第一条记录的下标是0

**3、计算下标**  
假设每页显示3条记录:  
第1页:limit 0,3 (012)  
第2页:limit 3,3 (345)  
第3页:limit 6,3(678)  
第4页:limit 9,3 (910 11)  
…

假设每页显示pageSize条记录，第pageNum页，使用limit表示：

limit (pageNum-1)*pageSize，pageSize

**4、小细节**

select * from t car limit 2; 和 select * from t car limit 0，2;是等效的。

## 二、MyBatis使用分页插件PageHelper ##

**1、引入分页插件pagehelper的依赖**

<dependency>
              <groupId>com.github.pagehelper</groupId>
              <artifactId>pagehelper</artifactId>
              <version>5.3.1</version>
          </dependency>

**2、mybatis-cofig.xml配置mybatis分页的拦截器**

plugin interceptor="com.github.pagehelper.PageInterceptor"

完整配置如下：

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        <properties resource="jdbc.properties"/>
        <settings>
            <setting name="lazyLoadingEnabled" value="true"/>
        </settings>
        <typeAliases>
            <package name="com.powernode.mybatis.pojo" />
        </typeAliases>
        
        <plugins>
            <plugin interceptor="com.github.pagehelper.PageInterceptor">			       </plugin>
        </plugins>
        <environments default="dev">
            <environment id="dev">
                <transactionManager type="JDBC"/>
                <dataSource type="POOLED">
                    <property name="driver" value="${jdbc.driver}"/>
                    <property name="url" value="${jdbc.url}"/>
                    <property name="username" value="${jdbc.username}"/>
                    <property name="password" value="${jdbc.password}"/>
                </dataSource>
            </environment>
        </environments>
        <mappers>
            <package name="com.powernode.mybatis.mapper"/>
        </mappers>
    </configuration>

**3、pojo类Clazz**

public class Clazz implements Serializable {
        
        private Integer cid;
        private String name;
        ......此处省略get、set方法
    }

4、ClazzMapper 接口

public interface ClazzMapper {
        
    
        List<Clazz> selectAll();
    
    }

**5、ClazzMapper.xml文件**

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.powernode.mybatis.mapper.ClazzMapper">
        <select id="selectAll" resultType="Clazz">
            select * from t_clazz
        </select>
    </mapper>

6、测试类趴一下  
记得在查询sql之前，加上这句PageHelper.startPage(pageNum,pageSize);相当于开启PageHelper，否则分页不会生效。

@Test
        public void testAll(){
        
            SqlSession sqlSession = SqlSessionUtil.openSqlSession();
            ClazzMapper mapper = sqlSession.getMapper(ClazzMapper.class);
            int pageNum = 2;
            int pageSize = 2;
            PageHelper.startPage(pageNum,pageSize);
            List<Clazz> clazzes = mapper.selectAll();
            clazzes.forEach(e-> System.out.println(e));
            sqlSession.close();
        }

运行结果  
![在这里插入图片描述][46838f48694e48dfb31dc1504b6ca86e.png]

如果需要更加详细的信息，可以使用PageInfo对象来处理：  
PageInfo pageInfo = new PageInfo<>(clazzes,4)

@Test
        public void testAll(){
        
            SqlSession sqlSession = SqlSessionUtil.openSqlSession();
            ClazzMapper mapper = sqlSession.getMapper(ClazzMapper.class);
            int pageNum = 2;
            int pageSize = 2;
            PageHelper.startPage(pageNum,pageSize);
            List<Clazz> clazzes = mapper.selectAll();
            PageInfo<Clazz> pageInfo = new PageInfo<>(clazzes,4);
            System.out.println(pageInfo);
            sqlSession.close();
        }

运行结果，会有非常详细的分页查询信息

PageInfo{
        pageNum=2, pageSize=2, size=2, startRow=3, endRow=4, total=10, pages=5, list=Page{
        count=true, pageNum=2, pageSize=2, startRow=2, endRow=4, total=10, pages=5, reasonable=false, pageSizeZero=false}[Clazz{
        cid=1003, name='高三三班', stus=null}, Clazz{
        cid=1004, name='高三四班', stus=null}], prePage=1, nextPage=3, isFirstPage=false, isLastPage=false, hasPreviousPage=true, hasNextPage=true, navigatePages=4, navigateFirstPage=1, navigateLastPage=4, navigatepageNums=[1, 2, 3, 4]}

[Mybatis_mybatis]: https://blog.csdn.net/weixin_43860634/article/details/127138626
[Mybatis_mybatis 1]: https://blog.csdn.net/weixin_43860634/article/details/127143707
[Mybatis_mybatis_CURD]: https://blog.csdn.net/weixin_43860634/article/details/127153801
[Mybatis_mybatis 2]: https://blog.csdn.net/weixin_43860634/article/details/127166151
[Mybatis_Mybatis]: https://blog.csdn.net/weixin_43860634/article/details/127177579
[Mybatis_WEB_Mybatis]: https://blog.csdn.net/weixin_43860634/article/details/127189521
[Mybatis_Mybatis 1]: https://blog.csdn.net/weixin_43860634/article/details/127464146
[Mybatis_Mybatis 2]: https://blog.csdn.net/weixin_43860634/article/details/127476337
[Mybatis_Mybatis_SQL]: https://blog.csdn.net/weixin_43860634/article/details/127502209
[Mybatis_SqlSession_SqlSessionFactory_SqlSessionFactoryBuilder]: https://blog.csdn.net/weixin_43860634/article/details/127523712
[Mybatis_MyBatis]: https://blog.csdn.net/weixin_43860634/article/details/127582841
[Mybatis_MyBatis_association_lazyLoadingEnabled]: https://blog.csdn.net/weixin_43860634/article/details/127585161
[Mybatis_MyBatis 1]: https://blog.csdn.net/weixin_43860634/article/details/127591723
[Mybatis_MyBatis 2]: https://blog.csdn.net/weixin_43860634/article/details/127596564
[Mybatis_MyBatis 3]: https://blog.csdn.net/weixin_43860634/article/details/127597198
[Mybatis_MyBatis_EhCache]: https://blog.csdn.net/weixin_43860634/article/details/127600772
[Mybatis_MyBatis_PageHelper]: https://blog.csdn.net/weixin_43860634/article/details/127603415
[46838f48694e48dfb31dc1504b6ca86e.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/04/01/63be5fb039c645b39f9d4d5c379662ad.png