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2021
06-28

SpringBoot整合MyBatis超详细教程

1.整合MyBatis操作

前面一篇提到了SpringBoot整合基础的数据源JDBC、Druid操作,实际项目中更常用的还是MyBatis框架,而SpringBoot整合MyBatis进行CRUD也非常方便。

下面从配置模式、注解模式、混合模式三个方面进行说明MyBatis与SpringBoot的整合。

1.1.配置模式

MyBatis配置模式是指使用mybatis配置文件的方式与SpringBoot进行整合,相对应的就有mybatis-config.xml(用于配置驼峰命名,也可以省略这个文件)、XxxMapper.xml文件。

主要步骤为:

  • 导入mybatis官方starter
  • 编写mapper接口。标准@Mapper注解
  • 编写sql映射文件并绑定mapper接口

在application.yaml中指定Mapper配置文件的位置,以及指定全局配置文件的信息 (建议;配置在mybatis.configuration中,可以省略mybatis-config.xml文件)

下面是具体整合配置步骤:

①引入相关依赖pom.xml配置:

pom.xml

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

        <!--整合mybatis-->
        <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.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </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>
    </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>

②编写对应Mapper接口:

@Mapper  //这个注解表示了这个类是一个mybatis的mapper接口类
@Repository
public interface UserMapper {
    //@Select("select * from user")
    List<User> findAllUsers();

    //@Insert("insert into user(id, username, password) values (#{id}, #{username}, #{password})")
    void insert(User user);

    //@Update("update user set username = #{username}, password = #{password} where id = #{id}")
    void update(User user);

    //@Delete("delete from user where id = #{id}")
    void deleteById(Integer id);
}

③在resources下创建对应的mapper文件,对应domain类,数据库表单如下:

User类:

@Data
public class User {
    private Integer id;
    private String username;
    private String password;
}

数据库user表:

UserMapper.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">
<!--namespace表示当前mapper的唯一标识:一般使用domain的全路径名+Mapper来命名-->
<mapper namespace="com.fengye.springboot_mybatis.mapper.UserMapper">
    <!--id:方法表示,一般配置对应的方法;
        resultType:表示该方法有返回,返回需要封装到对应实体的类型-->
    <select id="findAllUsers" resultType="com.fengye.springboot_mybatis.entity.User">
        select * from user
    </select>

    <insert id="insert" parameterType="com.fengye.springboot_mybatis.entity.User">
        insert into user(id, username, password) values (#{id}, #{username}, #{password})
    </insert>

    <update id="update" parameterType="com.fengye.springboot_mybatis.entity.User">
        update user set username = #{username}, password = #{password} where id = #{id}
    </update>

    <delete id="deleteById" parameterType="Integer">
        delete from user where id = #{id}
    </delete>
</mapper>

④对应配置application.yml文件:

application.yml

server:
  port: 8083

spring:
  datasource:
    username: root
    password: admin
    #假如时区报错,增加时区配置serverTimezone=UTC
    url: jdbc:mysql://localhost:3306/mybatis02_0322?serverTimezone=UTC&useUnicode=true&characterEncoding=utf-8
    driver-class-name: com.mysql.cj.jdbc.Driver

mybatis:
  #config-location: classpath:mybatis/mybatis-config.xml  使用了configuration注解则无需再指定mybatis-config.xml文件
  mapper-locations: classpath:mybatis/mapper/*.xml
  configuration:   #指定mybatis全局配置文件中的相关配置项
    map-underscore-to-camel-case: true

1.2.注解模式

注解模式使用

主要步骤:

  • 导入mybatis官方依赖
  • 注解方式编写mapper接口
  • 在application.yaml中指定Mapper配置文件的位置,以及指定全局配置文件的信息

可以看到注解模式比配置模式少了编写Mapper.xml文件,简化了简单SQL语句的xml文件编写。

下面是具体整合步骤:

①创建测试表单city,对应domain类:

建表sql:

CREATE TABLE city
(
    id    INT(11) PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(30),
    state VARCHAR(30),
    country VARCHAR(30)
);

City类:

@Data
public class City {
    private Long id;
    private String name;
    private String state;
    private String country;
}

②导入pom.xml与配置模式相同,编写注解式CityMapper接口:

@Mapper
@Repository
public interface CityMapper {
    @Select("select * from city where id = #{id}")
    public City getCityById(Long id);

    /**
     * 使用@Options来增加除Insert语句中其它可选参数,比如插入获取id主键的值
     * @param city
     */
    @Insert("insert into city(name, state, country) values (#{name}, #{state}, #{country})")
    @Options(useGeneratedKeys = true, keyProperty = "id")
    public void insert(City city);

    @Update("update city set name = #{name}, state = #{state}, country = #{country} where id = #{id}")
    public void update(City city);

    @Delete("delete from city where id = #{id}")
    public void deleteById(Long id);
}

③编写Service层、Controller层:

Service相关:

public interface CityService {
    City findCityById(Long id);

    void insert(City city);

    void update(City city);

    void deleteById(Long id);
}


@Service
public class CityServiceImpl implements CityService {
    @Autowired
    private CityMapper cityMapper;

    @Override
    public City findCityById(Long id) {
        return cityMapper.getCityById(id);
    }

    @Override
    public void insert(City city) {
        cityMapper.insert(city);
    }

    @Override
    public void update(City city) {
        cityMapper.update(city);
    }

    @Override
    public void deleteById(Long id) {
        cityMapper.deleteById(id);
    }
}

Controller相关:

@RestController
@RequestMapping("/city/api")
public class CityController {
    @Autowired
    private CityService cityService;

    @RequestMapping("/findCityById/{id}")
    public City findCityById(@PathVariable("id") Long id){
        return cityService.findCityById(id);
    }

    @PostMapping("/insert")
    public String insert(City city){
        cityService.insert(city);
        return "insert ok";
    }

    @PostMapping("/update")
    public String update(City city){
        cityService.update(city);
        return "update ok";
    }

    @GetMapping("/delete/{id}")
    public String delete(@PathVariable("id") Long id){
        cityService.deleteById(id);
        return "delete ok";
    }
}

④对应使用Postman接口进行测试:

简单模拟接口POST/GET请求即可:

1.3.混合模式

在实际项目开发中涉及很多复杂业务及连表查询SQL,可以配合使用注解与配置模式,达到最佳实践的目的。

实际项目操作步骤:

  • 引入mybatis-starter
  • 配置application.yaml中,指定mapper-location位置即可
  • 编写Mapper接口并标注@Mapper注解
  • 简单方法直接注解方式
  • 复杂方法编写mapper.xml进行绑定映射
  • 主启动类上使用@MapperScan("com.fengye.springboot_mybatis.mapper") 简化Mapper接口,包下所有接口就可以不用标注@Mapper注解

具体配置如下:

@SpringBootApplication
//主启动类上标注,在XxxMapper中可以省略@Mapper注解
@MapperScan("com.fengye.springboot_mybatis.mapper")
public class SpringbootMybatisApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringbootMybatisApplication.class, args);
    }

}


@Repository
public interface CityMapper {
    @Select("select * from city where id = #{id}")
    public City getCityById(Long id);

    /**
     * 使用@Options来增加除Insert语句中其它可选参数,比如插入获取id主键的值
     * @param city
     */
    @Insert("insert into city(name, state, country) values (#{name}, #{state}, #{country})")
    @Options(useGeneratedKeys = true, keyProperty = "id")
    public void insert(City city);

    @Update("update city set name = #{name}, state = #{state}, country = #{country} where id = #{id}")
    public void update(City city);

    @Delete("delete from city where id = #{id}")
    public void deleteById(Long id);
}

本博客参考写作文档:

SpringBoot2核心技术与响应式编程

博客涉及代码示例均已上传至github地址:

SpringBootStudy

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