22. SpringBoot 集成 Mybatis

1. 引入Mybatis的maven 依赖

<dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>1.3.2</version>
</dependency>

2. MybatisGenerator自动生成Mapper、dao、model

3. MapperDao上标注@Mapper注解

@Mapper
public interface UserMapper {
    int deleteByPrimaryKey(Integer id);

    int insert(User record);

    int insertSelective(User record);

    User selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(User record);

    int updateByPrimaryKey(User record);
}

4. 配置文件中指明mybatis的配置文件位置

UserMapper.xml配置文件方式实现时，需要制定配置文件位置

#MapperDaoInterface若是用注解的方式实现SQL的话就用不着/mapper/*.xml配置
mybatis:
  mapper-locations: classpath:mybatis/mapper/*.xml
  config-location: classpath:mybatis/mybatis-config.xml
  configuration:
    map-underscore-to-camel-case: true #开启驼峰标识 表：user_name  --->  JavaBean：userName

#配置com.example.jdbc.dao包下的mapper接口类的日志级别，配上此日志控制台会打印SQL
logging:
  level:
    com:
      example:
        jdbc:
          dao: debug

注意：2.1.3.RELEASE版本的springboot中，mybatis.configuration 和mybatis.configLocation 配置项不可以一起使用

Caused by: java.lang.IllegalStateException: Property 'configuration' and 'configLocation' can not specified with together
    at org.springframework.util.Assert.state(Assert.java:) ~[spring-core-5.1..RELEASE.jar:5.1..RELEASE]
    at org.mybatis.spring.SqlSessionFactoryBean.afterPropertiesSet(SqlSessionFactoryBean.java:) ~[mybatis-spring-2.0..jar:2.0.]
    at org.mybatis.spring.SqlSessionFactoryBean.getObject(SqlSessionFactoryBean.java:) ~[mybatis-spring-2.0..jar:2.0.]
    at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration.sqlSessionFactory(MybatisAutoConfiguration.java:) ~[mybatis-spring-boot-autoconfigure-2.0..jar:2.0.]
    at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$99dc0108.CGLIB$sqlSessionFactory$(<generated>) ~[mybatis-spring-boot-autoconfigure-2.0..jar:2.0.]
    at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$99dc0108$$FastClassBySpringCGLIB$$677faa16.invoke(<generated>) ~[mybatis-spring-boot-autoconfigure-2.0..jar:2.0.]
    at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:) ~[spring-core-5.1..RELEASE.jar:5.1..RELEASE]
    at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:) ~[spring-context-5.1..RELEASE.jar:5.1..RELEASE]
    at org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration$$EnhancerBySpringCGLIB$$99dc0108.sqlSessionFactory(<generated>) ~[mybatis-spring-boot-autoconfigure-2.0..jar:2.0.]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_181]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:) ~[na:1.8.0_181]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:) ~[na:1.8.0_181]
    at java.lang.reflect.Method.invoke(Method.java:) ~[na:1.8.0_181]
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:) ~[spring-beans-5.1..RELEASE.jar:5.1..RELEASE]
    ...  common frames omitted

5. 不用配置文件，用注解

@Mapper
public interface UserMapper {

    @Delete("delete from user where id = #{id}")
    int deleteByPrimaryKey(Integer id);

    @Insert("insert into user(name,age,sex) values(#{name},#{age},#{sex})")
    int insert(User record);

    int insertSelective(User record);

    @Select("select * from user where id = #{id}")
    User selectByPrimaryKey(Integer id);

    int updateByPrimaryKeySelective(User record);

    @Update("update user set name=#{name}, age=#{age}, sex=#{sex}")
    int updateByPrimaryKey(User record);
}

@MapperScan注解与@Mapper注解选其一用即可

直接在Mapper类上面添加注解@Mapper，这种方式要求每一个mapper类都需要添加此注解，麻烦。

通过使用@MapperScan可以指定要扫描的Mapper类的包的路径,可以解决mapper类没有在Spring Boot主程序的情况

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
@MapperScan("com.example.jdbc.dao")
public class SpringBootJdbcApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootJdbcApplication.class, args);
    }
}

@MapperScan 支持多个包扫描和包名模糊匹配
@MapperScan({"com.kfit.demo","com.kfit.user"}) 
@MapperScan({"com.kfit.*.mapper","org.kfit.*.mapper"})