3、整合MyBatis操作

https://github.com/mybatis
starter
SpringBoot官方的Starter：spring-boot-starter-
第三方的： -spring-boot-starte

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

3.1 配置模式

# 配置mybatis规则
mybatis:
  config-location: classpath:mybatis/mybatis-config.xml  #全局配置文件位置
  mapper-locations: classpath:mybatis/mapper/*.xml  #sql映射文件位置

<?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>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="${driver}"/>
        <property name="url" value="${url}"/>
        <property name="username" value="${username}"/>
        <property name="password" value="${password}"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="org/mybatis/example/BlogMapper.xml"/>
  </mappers>
</configuration>

Mapper接口--->绑定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.atguigu.admin.mapper.AccountMapper">
<!--    public Account getAcct(Long id); -->
    <select id="getAcct" resultType="com.atguigu.admin.bean.Account">
        select * from  account_tbl where  id=#{id}
    </select>
</mapper>

在mapper类表上@@Mapper注解

@Mapper
public interface BookMapper {

    public Admin getAdmin(Long id);
}

也可以在主程序类中用@MapperScan扫描所有Mapper

@MapperScan("com.hao.admin.mapper")
//@ServletComponentScan(basePackages = "com.hao")
@SpringBootApplication
public class Boot05WebAdminApplication {

    public static void main(String[] args) {
        SpringApplication.run(Boot05WebAdminApplication.class, args);
    }

}

配置 private Configuration configuration; mybatis.configuration下面的所有，就是相当于改mybatis全局配置文件中的值

# 配置mybatis规则
mybatis:
#  config-location: classpath:mybatis/mybatis-config.xml
  mapper-locations: classpath:mybatis/mapper/*.xml
  configuration:
    map-underscore-to-camel-case: true

 可以不写全局；配置文件，所有全局配置文件的配置都放在configuration配置项中即可

写了mybatis.configuration后就不能指定全局配置文件mybatis-config.xml，两者只能存在一个

3.2 注解模式

@Mapper
public interface CityMapper {

    @Select("select * from city where id=#{id}")
    public City getById(Long id);

    public void insert(City city);

}

3.3 混合模式

@Mapper
public interface CityMapper {

    @Select("select * from city where id=#{id}")
    public City getById(Long id);

    public void insert(City city);

}

<?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.hao.admin.mapper.CityMapper">

    <insert id="insert" useGeneratedKeys="true" keyProperty="id">
        insert into city(`name`,`state`,`country`) values (#{name},#{state},#{country})
    </insert>
</mapper>

最佳实战：

• 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
• @MapperScan(“com.atguigu.admin.mapper”) 简化，其他的接口就可以不用标注@Mapper注解