SpringBoot整合Mybatis（开启驼峰映射、分页）

旧城等待， 2023-10-14 16:26 8阅读 0赞

**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 ###

![d8cf14c50a7e459581f856fb4868d0d6.png][]

### 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>2.2.5.RELEASE</version>
            <relativePath/> 
        </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>
                 
                <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>
    
    
    
    
    
    
    
    
    
    
    
        </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>

![1b4dbb92b4004387baf1071bdc549f5e.png][]

> 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**

<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；

![deab2cafa90243dba6eb61fe3b061e27.png][]

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 ###

![fcec675a20d04a60a27f3d2d1265fd6e.png][]

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）

### 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>
            
            <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

![0a33854b56da481c9614f24e85c6de42.png][]

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

![0031867944fd415f80fafa98f44c7f40.png][]

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>2.2.5.RELEASE</version>
            <relativePath/> 
        </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>
    
               
                <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>
    
    
    
    
    
    
    
    
    
    
    
            </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 ###

### 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！

[d8cf14c50a7e459581f856fb4868d0d6.png]: https://img-blog.csdnimg.cn/d8cf14c50a7e459581f856fb4868d0d6.png
[1b4dbb92b4004387baf1071bdc549f5e.png]: https://img-blog.csdnimg.cn/1b4dbb92b4004387baf1071bdc549f5e.png
[deab2cafa90243dba6eb61fe3b061e27.png]: https://img-blog.csdnimg.cn/deab2cafa90243dba6eb61fe3b061e27.png
[fcec675a20d04a60a27f3d2d1265fd6e.png]: https://img-blog.csdnimg.cn/fcec675a20d04a60a27f3d2d1265fd6e.png
[mybatis]: https://so.csdn.net/so/search?q=mybatis&spm=1001.2101.3001.7020
[0a33854b56da481c9614f24e85c6de42.png]: https://img-blog.csdnimg.cn/0a33854b56da481c9614f24e85c6de42.png
[0031867944fd415f80fafa98f44c7f40.png]: https://img-blog.csdnimg.cn/0031867944fd415f80fafa98f44c7f40.png