目录

Mybatis的简单使用

依赖

 项目结构

父pom文件

 pom文件

配置文件

实体类

controller

mapper

xml

结果

mybatis开启驼峰映射

 方式一：

方式二：

方式三：

方式四： 

MyBatis结合PageHelper进行分页

父pom文件

pom文件

配置文件

MyBatisConfig

 controller

结果

---

Mybatis的简单使用

 本示例为父子项目演示：

依赖

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.4</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

 项目结构

父pom文件

注意：父pom中 starter-web和starter-test不需要

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <!--        <version>3.1.2</version>-->
        <version>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.chensir</groupId>
    <artifactId>springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot</name>
    <description>springboot</description>
    <properties>
        <java.version>8</java.version>
        <hutool.version>5.8.3</hutool.version>
        <lombok.version>1.18.24</lombok.version>
        <alibaba-sdk.version>2.0.0</alibaba-sdk.version>
    </properties>

    <packaging>pom</packaging>

    <modules>
        <module>servlet</module>
        <module>spring-interceptor</module>
        <module>spring-aop</module>
        <module>spring-united-reslut</module>
        <module>spring-jdbc</module>
        <module>spring-mybatis</module>
    </modules>

    <dependencyManagement>
        <dependencies>
             <!--钉钉机器人消息-->
            <dependency>
                <groupId>com.aliyun</groupId>
                <artifactId>alibaba-dingtalk-service-sdk</artifactId>
                <version>${alibaba-sdk.version}</version>
            </dependency>

            <dependency>
                <groupId>cn.hutool</groupId>
                <artifactId>hutool-all</artifactId>
                <version>${hutool.version}</version>
            </dependency>

            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>${lombok.version}</version>
            </dependency>

<!--            <dependency>-->
<!--                <groupId>org.springframework.boot</groupId>-->
<!--                <artifactId>spring-boot-starter-web</artifactId>-->
<!--            </dependency>-->

<!--            <dependency>-->
<!--                <groupId>org.springframework.boot</groupId>-->
<!--                <artifactId>spring-boot-starter-test</artifactId>-->
<!--                <scope>test</scope>-->
<!--            </dependency>-->
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

 pom文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.chensir</groupId>
        <artifactId>springboot</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <artifactId>spring-mybatis</artifactId>

    <dependencies>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.4</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
             <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter-test</artifactId>
            <version>2.1.4</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

错误再现

 本人在这入了个坑，刚开始子项目中引入lombok依赖后版本为1.18.12，而父pom文件中版本是1.18.24；结果调用接口时提示说实体类在SpringMvc中转换异常！好家伙，这我也联想不到是lombok的原因啊。所以就一直排查问题（几个小时后）我把实体类中@data去掉后 手动写入@set、@get等方，接口就完全通了！由此开始去看@lombok注解 才发现子项目中引入

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
     <optional>true</optional>
</dependency>

这个注解后，子项目中lombok依赖版本就变成了1.18.12。然后接口就还报那个错误！把依赖注释掉，子项目中lombok依赖版本继承父项目版本为1.18.24，接口可以调通；但是过一会 我把子项目中lombok依赖又加上，发现lombok的版本又不会改变了（1.18.24），刷新maven、重启idea还是不会变！这他娘的让我摸不着头脑！真奇葩啊！

最后我在父pom中使用<dependencyManagement></dependencyManagement>去管理依赖版本，防止父子依赖版本不对而冲突！

dependencyManagement里只是声明依赖，并不自动实现引入，因此子项目需要显示的声明需要用的依赖。如果不在子项目中声明依赖，是不会从父项目中继承下来的；只有在子项目中写了该依赖项，并且没有指定具体版本，才会从父项目中继承该项，并且version和scope都读取自父pom;另外如果子项目中指定了版本号，那么会使用子项目中指定的jar版本。

这个原因就是父pom中引用了

<!--父pom中不要加此依赖，否则依赖clean会报错，原因是父pom中并没指定版本-->
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
            </dependency>

            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>

这两个依赖；并且这俩注解也没指定版本，以至于子pom中找不到版本号；

在clean右键 Run Maven Build时会报全部的子项目中找不到starter-web、starter-test版本号；在父pom中去掉这两个依赖即可！

 

配置文件

spring.datasource.url=jdbc:mysql://localhost:3306/db1?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8&useSSL=true
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

mybatis.mapper-locations = classpath*:mapper/*Mapper.xml

实体类

@Data
public class Users {

    private Long id;

    private String name;

    private Integer age;

    private String sex;

    private String tel;

    // 数据库timestamp类型时间转化java规定格式时间
    @JsonFormat(timezone = "GMT+8",pattern = "yyyy-MM-dd")
    // 接受前端表单传递过来的字符串类型的时间数
    @DateTimeFormat(pattern = "yyyy-MM-dd")
    private Date createTime;

    @JsonFormat(timezone = "GMT+8",pattern = "yyyy-MM-dd")
    @DateTimeFormat(pattern = "yyyy-MM-dd")
    private LocalDateTime updateTime;
}

controller

@RestController
public class UsersController {

    @Resource
    private UsersService usersService;

    @GetMapping("/demo1")
    public List<Users> selectUsersList() {
        List<Users> users = usersService.selectUsersList();
        return users;
    }

    @GetMapping("/demo2")
    public Users selectUsers(){
        Users users = usersService.selectUsers();
        return users;
    }

    @GetMapping("/demo3")
    public Map selectUsersToMap(){
        return usersService.selectUsersToMap();
    }
}

mapper

@Mapper
public interface UsersMapper {

    List<Users> selectUsersList();

    Users selectUsers();

    Map<String,Object> selectUsersToMap();
}

xml

<?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.chensir.mapper.UsersMapper">


    <select id="selectUsersList" resultType="com.chensir.entity.Users">
        select * from users
    </select>
    <select id="selectUsers" resultType="com.chensir.entity.Users">
        select * from users where id = 1
    </select>
    <select id="selectUsersToMap" resultType="java.util.Map">
        select * from users where id = 1
    </select>
</mapper>

结果

查询后发现时间为null！这是因为mybatis需要开启驼峰映射，默认是关闭的（mybatis-plus默认是开启的）；

mybatis开启驼峰映射

 方式一：

在xml中做映射（本人不喜欢这样写法）

<resultMap type="com.chensir.entity.Users" id="resultList">
        <result property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="createTime" column="create_time"/>
 
</resultMap>

方式二：

mybatis-config.xml文件：但是使用SpringBoot后这中方式也不常使用

<?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>
    <settings>
        <!-- 开启驼峰，开启后，只要数据库字段和对象属性名字母相同，无论中间加多少下划线都可以识别 -->
        <setting name="mapUnderscoreToCamelCase" value="true" />
    </settings>
</configuration>

方式三：

在配置文件中配置

mybatis.mapper-locations = classpath*:mapper/*Mapper.xml
#开启驼峰映射
mybatis.configuration.map-underscore-to-camel-case=true

mybatis-plus配置（mybatis-plus默认是开启的）

mybatis-plus:
  configuration:
    #在映射实体或者属性时，将数据库中表名和字段名中的下划线去掉，按照驼峰命名法映射 address_book ---> addressBook
    map-underscore-to-camel-case: true

注意：如果SqlSessionFactory自己手动配置后，无论配置文件中配置的扫描 Mapper.xml还是开启驼峰映射都会失效，这时就需要在cofnig中手动配置并注入，详见方式四；

方式四： 

手动配置SqlSessionFactory并往SqlSessionFactory注入扫描Mapper.xml、驼峰映射等；

手动配置SqlSessionFactory后自动装配就不会使用官方的，启动项目后会先扫描自己注册的！

package com.chensir.config;

import com.github.pagehelper.PageInterceptor;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.boot.autoconfigure.ConfigurationCustomizer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.util.CollectionUtils;

import javax.sql.DataSource;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

@Configuration
@Slf4j
public class MyBatisConfig {

    @Autowired
    private ConfigurationCustomizer configurationCustomizer;
    /**
     * 自己注册SqlSessionFactory 目的是增强功能，添加分页插件
     * @param ds 代表数据源
     * @return
     * @throws Exception
     */
    @Bean
    public SqlSessionFactory sqlSessionFactory(DataSource ds) throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        // 设置数据源
        factoryBean.setDataSource(ds);

        // 把分页插件设置到SqlSessionFactory插件库
        factoryBean.setPlugins(new PageInterceptor());
        // 配置mapper.xml地址
        factoryBean.setMapperLocations(resolveMapperLocations());

        //驼峰映射注册到SqlSessionFactory中
        org.apache.ibatis.session.Configuration configuration = new org.apache.ibatis.session.Configuration();
        configurationCustomizer.customize(configuration);
        factoryBean.setConfiguration(configuration);


        // 返回具体实例对象
        SqlSessionFactory bean = factoryBean.getObject();
        return bean;
    }


    /**
     * 开启驼峰映射
     * @return
     */
    @Bean
    public ConfigurationCustomizer configurationCustomizer(){
        return new ConfigurationCustomizer() {
            @Override
            public void customize(org.apache.ibatis.session.Configuration configuration) {
                configuration.setMapUnderscoreToCamelCase(true);
            }
        };
    }

    /**
     * 查找 xxxMapper.xml
     * @return
     */
    public Resource[] resolveMapperLocations() {
        ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();
        List<String> mapperLocations = new ArrayList<>();
        mapperLocations.add("classpath*:mapper/*Mapper.xml");
//        mapperLocations.add("classpath*:com/meiwei/ping/dao/**/*Mapper.xml");
        List<Resource> resources = new ArrayList();
        if (!CollectionUtils.isEmpty(mapperLocations)) {
            for (String mapperLocation : mapperLocations) {
                try {
                    Resource[] mappers = resourceResolver.getResources(mapperLocation);
                    resources.addAll(Arrays.asList(mappers));
                } catch (IOException e) {
                    log.error("Get myBatis resources happened exception", e);
                }
            }
        }

        return resources.toArray(new Resource[resources.size()]);
    }

}

MyBatis结合PageHelper进行分页

使用pagehelper进行分页时起初我并没有自己注入SqlSessionFactory，而是使用官方的；但是在

 users强转page时会报强转错误；于是乎我开始使用PageInfo方式；

 虽然不报错了，结果能分页了，但是页码和条数不生效！ 唉，一波未停一波又起啊！

于是乎，我又开始去手动配置SqlSessionFactory（MyBatisConfig），并且把扫描xxxMapper.xml、驼峰映射注入；详细流程请看下方代码。

父pom文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <!--        <version>3.1.2</version>-->
        <version>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.chensir</groupId>
    <artifactId>springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot</name>
    <description>springboot</description>
    <properties>
        <java.version>8</java.version>
        <hutool.version>5.8.3</hutool.version>
        <lombok.version>1.18.24</lombok.version>
        <alibaba-sdk.version>2.0.0</alibaba-sdk.version>
    </properties>

    <packaging>pom</packaging>

    <modules>
        <module>servlet</module>
        <module>spring-interceptor</module>
        <module>spring-aop</module>
        <module>spring-united-reslut</module>
        <module>spring-jdbc</module>
        <module>spring-mybatis</module>
    </modules>

    <dependencyManagement>
        <dependencies>

           <!--钉钉机器人消息-->
            <dependency>
                <groupId>com.aliyun</groupId>
                <artifactId>alibaba-dingtalk-service-sdk</artifactId>
                <version>${alibaba-sdk.version}</version>
            </dependency>

            <dependency>
                <groupId>cn.hutool</groupId>
                <artifactId>hutool-all</artifactId>
                <version>${hutool.version}</version>
            </dependency>

            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>${lombok.version}</version>
            </dependency>
<!--父pom中不要加此依赖，否则依赖clean会报错，原因是父pom中并没指定版本-->
<!--            <dependency>-->
<!--                <groupId>org.springframework.boot</groupId>-->
<!--                <artifactId>spring-boot-starter-web</artifactId>-->
<!--            </dependency>-->

<!--            <dependency>-->
<!--                <groupId>org.springframework.boot</groupId>-->
<!--                <artifactId>spring-boot-starter-test</artifactId>-->
<!--                <scope>test</scope>-->
<!--            </dependency>-->
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

pom文件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>com.chensir</groupId>
        <artifactId>springboot</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <relativePath>../pom.xml</relativePath>
    </parent>

    <artifactId>spring-mybatis</artifactId>

    <dependencies>
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>5.1.10</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.4</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
             <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter-test</artifactId>
            <version>2.1.4</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

配置文件

spring.datasource.url=jdbc:mysql://localhost/db1?useUnicode=true&characterEncoding=utf8&zeroDateTimeBehavior=convertToNull&useSSL=true&serverTimezone=GMT%2B8&autoReconnect=true&rewriteBatchedStatements=true
spring.datasource.username=root
spring.datasource.password=root
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

MyBatisConfig

package com.chensir.config;

import com.github.pagehelper.PageInterceptor;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.boot.autoconfigure.ConfigurationCustomizer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.util.CollectionUtils;

import javax.sql.DataSource;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

@Configuration
@Slf4j
public class MyBatisConfig {

    @Autowired
    private ConfigurationCustomizer configurationCustomizer;
    /**
     * 自己注册SqlSessionFactory 目的是增强功能，添加分页插件
     * @param ds 代表数据源
     * @return
     * @throws Exception
     */
    @Bean
    public SqlSessionFactory sqlSessionFactory(DataSource ds) throws Exception {
        SqlSessionFactoryBean factoryBean = new SqlSessionFactoryBean();
        // 设置数据源
        factoryBean.setDataSource(ds);

        // 把分页插件设置到SqlSessionFactory插件库
        factoryBean.setPlugins(new PageInterceptor());
        // 配置mapper.xml地址
        factoryBean.setMapperLocations(resolveMapperLocations());

        //驼峰映射注册到SqlSessionFactory中
        org.apache.ibatis.session.Configuration configuration = new org.apache.ibatis.session.Configuration();
        configurationCustomizer.customize(configuration);
        factoryBean.setConfiguration(configuration);


        // 返回具体实例对象
        SqlSessionFactory bean = factoryBean.getObject();
        return bean;
    }


    /**
     * 开启驼峰映射
     * @return
     */
    @Bean
    public ConfigurationCustomizer configurationCustomizer(){
        return new ConfigurationCustomizer() {
            @Override
            public void customize(org.apache.ibatis.session.Configuration configuration) {
                configuration.setMapUnderscoreToCamelCase(true);
            }
        };
    }

    /**
     * 查找 xxxMapper.xml
     * @return
     */
    public Resource[] resolveMapperLocations() {
        ResourcePatternResolver resourceResolver = new PathMatchingResourcePatternResolver();
        List<String> mapperLocations = new ArrayList<>();
        mapperLocations.add("classpath*:mapper/*Mapper.xml");
//        mapperLocations.add("classpath*:com/meiwei/ping/dao/**/*Mapper.xml");
        List<Resource> resources = new ArrayList();
        if (!CollectionUtils.isEmpty(mapperLocations)) {
            for (String mapperLocation : mapperLocations) {
                try {
                    Resource[] mappers = resourceResolver.getResources(mapperLocation);
                    resources.addAll(Arrays.asList(mappers));
                } catch (IOException e) {
                    log.error("Get myBatis resources happened exception", e);
                }
            }
        }

        return resources.toArray(new Resource[resources.size()]);
    }

}

 controller

有PageInfo和Page两种方式

package com.chensir.controller;

import com.chensir.entity.Users;
import com.chensir.service.UsersService;
import com.github.pagehelper.Page;
import com.github.pagehelper.PageHelper;
import com.github.pagehelper.PageInfo;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@RestController
public class UsersController {

    @Resource
    private UsersService usersService;

    @GetMapping("/demo1")
    public Map selectUsersList(Integer pageNum,Integer pageSize) {

        // 启用分页，查询第一页，每页3条
        PageHelper.startPage(pageNum,pageSize);
        //-------------PageInfo方式---------------
//        PageInfo<Users> usersPageInfo = new PageInfo<>(usersService.selectUsersList());
//        return usersPageInfo;
        //-------------PageInfo方式---------------

        //-------------Page方式---------------
        List<Users> users = usersService.selectUsersList();
        Page page = (Page) users;
        int pages = page.getPages();
        long total = page.getTotal();


        Map<String,Object> pageMap = new HashMap<>();
        pageMap.put("pages",pages);
        pageMap.put("total",total);
        pageMap.put("items",users);
        return pageMap;
        //-------------Page方式---------------

    }

    @GetMapping("/demo2")
    public Users selectUsers(){
        Users users = usersService.selectUsers();
        return users;
    }

    @GetMapping("/demo3")
    public Map selectUsersToMap(){
        return usersService.selectUsersToMap();
    }
}

结果

{
  "total": 5,
  "pages": 2,
  "items": [
    {
      "id": 1,
      "name": "chjnzkcn",
      "age": 18,
      "sex": "男",
      "tel": "123",
      "createTime": "2023-05-11",
      "updateTime": "2023-05-11"
    },
    {
      "id": 2,
      "name": "czvfzsvdv",
      "age": 20,
      "sex": "男",
      "tel": "2315",
      "createTime": "2023-05-11",
      "updateTime": "2023-05-11"
    },
    {
      "id": 3,
      "name": "sczvszv",
      "age": 18,
      "sex": "女",
      "tel": "2112321",
      "createTime": "2023-05-11",
      "updateTime": "2023-05-11"
    }
  ]
}

但是这样的分页不足以满足我们的需要，在我们想要进行分页时需要重复撰写这样的代码，显然很不方便！下篇开始来对分页进行封装！