springboot整合mybatis多数据源 并用mapper接口的方式查询数据，sql写在xml中，给出xml配置样例 并给出具体代码

以下是一个简单的 Spring Boot 整合 MyBatis 多数据源的示例，其中使用了 Mapper 接口的方式查询数据，SQL 语句写在 XML 文件中。

首先，在 pom.xml 文件中添加以下依赖：

<dependencies>
    <!-- Spring Boot Starter -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>

    <!-- MyBatis Starter -->
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>2.2.0</version>
    </dependency>

    <!-- MySQL Connector -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.23</version>
    </dependency>
</dependencies>

然后，在 application.properties 文件中配置数据源：

# 主数据源
spring.datasource.primary.url=jdbc:mysql://localhost:3306/primary_db?useSSL=false&serverTimezone=UTC
spring.datasource.primary.username=root
spring.datasource.primary.password=root

# 从数据源
spring.datasource.secondary.url=jdbc:mysql://localhost:3306/secondary_db?useSSL=false&serverTimezone=UTC
spring.datasource.secondary.username=root
spring.datasource.secondary.password=root

接下来，创建两个数据源的配置类：

@Configuration
@MapperScan(basePackages = "com.example.mapper.primary", sqlSessionTemplateRef = "primarySqlSessionTemplate")
public class PrimaryDataSourceConfig {
    @Bean
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource.primary")
    public DataSource primaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    @Primary
    public SqlSessionFactory primarySqlSessionFactory(@Qualifier("primaryDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
        sessionFactoryBean.setDataSource(dataSource);
        sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath*:mapper/primary/*.xml"));
        return sessionFactoryBean.getObject();
    }

    @Bean
    @Primary
    public SqlSessionTemplate primarySqlSessionTemplate(@Qualifier("primarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

@Configuration
@MapperScan(basePackages = "com.example.mapper.secondary", sqlSessionTemplateRef = "secondarySqlSessionTemplate")
public class SecondaryDataSourceConfig {
    @Bean
    @ConfigurationProperties(prefix = "spring.datasource.secondary")
    public DataSource secondaryDataSource() {
        return DataSourceBuilder.create().build();
    }

    @Bean
    public SqlSessionFactory secondarySqlSessionFactory(@Qualifier("secondaryDataSource") DataSource dataSource) throws Exception {
        SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
        sessionFactoryBean.setDataSource(dataSource);
        sessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath*:mapper/secondary/*.xml"));
        return sessionFactoryBean.getObject();
    }

    @Bean
    public SqlSessionTemplate secondarySqlSessionTemplate(@Qualifier("secondarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) {
        return new SqlSessionTemplate(sqlSessionFactory);
    }
}

其中，@MapperScan 注解用于扫描 Mapper 接口，sqlSessionTemplateRef 属性用于指定使用的 SqlSessionTemplate。

最后，创建 Mapper 接口和 XML 文件：

@Mapper
public interface UserMapper {
    @Select("SELECT * FROM user")
    List<User> findAll();
}

@Mapper
public interface OrderMapper {
    @Select("SELECT * FROM `order`")
    List<Order> findAll();
}

<mapper namespace="com.example.mapper.primary.UserMapper">
    <resultMap id="BaseResultMap" type="com.example.entity.User">
        <id column="id" property="id" jdbcType="INTEGER"/>
        <result column="name" property="name" jdbcType="VARCHAR"/>
        <result column="age" property="age" jdbcType="INTEGER"/>
    </resultMap>

    <select id="findAll" resultMap="BaseResultMap">
        SELECT * FROM user
    </select>
</mapper>

<mapper namespace="com.example.mapper.secondary.OrderMapper">
    <resultMap id="BaseResultMap" type="com.example.entity.Order">
        <id column="id" property="id" jdbcType="INTEGER"/>
        <result column="name" property="name" jdbcType="VARCHAR"/>
        <result column="price" property="price" jdbcType="DECIMAL"/>
    </resultMap>

    <select id="findAll" resultMap="BaseResultMap">
        SELECT * FROM `order`
    </select>
</mapper>

这样，就完成了 Spring Boot 整合 MyBatis 多数据源的配置。在需要使用数据源的地方，只需要注入对应的 Mapper 接口即可。

参考资料：

- [Spring Boot 整合 MyBatis 多数据源](https://www.cnblogs.com/zhaozihan/p/10900886.html)