SpringBoot + MyBatis使用多数据源

阳光穿透心脏的1/2处 2021-10-14 05:44 441阅读 0赞

## SpringBoot + MyBatis使用多数据源 ##

有时候我们需要在一个项目里面集成一个或者多个数据源。

### 实现的思想 ###

*  使用`mybatis`持久层框架
 *  `mybatis`的运行需要依赖于几个组件
    
     *  `DataSource` 数据源
     *  `DataSourceTransactionManager` 事务管理器
     *  `SqlSessionFactory` SqlSession工厂，负责创建SqlSession
     *  `SqlSessionTemplate` SqlSession，负责执行crud
 *  多数据源，就是使用多个数据源，多个事务管理器，多个SqlSession工厂，就有不同的SqlSession

### Maven ###

> 使用Druid作为数据源

<dependencies>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>mysql</groupId>
    			<artifactId>mysql-connector-java</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.mybatis.spring.boot</groupId>
    			<artifactId>mybatis-spring-boot-starter</artifactId>
    			<version>2.0.0</version>
    		</dependency>
    		<dependency>
    			<groupId>com.alibaba</groupId>
    			<artifactId>druid</artifactId>
    			<version>1.1.14</version>
    		</dependency>
    	</dependencies>

### application.yml ###

> 配置多个数据源，这里仅仅配置了基本必须的属性

logging:
      level:
        root: debug
    
    datasource:
      1:
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/springboot1?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&serverTimezone=GMT%2b8
        username: root
        password: root
      
      2:
        driver-class-name: com.mysql.cj.jdbc.Driver
        url: jdbc:mysql://localhost:3306/springboot2?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&serverTimezone=GMT%2b8
        username: root
        password: root

### 多个数据源的@Configuration 配置 ###

第一个数据源以及持久层需要的组件

package io.springboot.multidatasource.configuration;
    
    import javax.sql.DataSource;
    
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.mybatis.spring.SqlSessionFactoryBean;
    import org.mybatis.spring.SqlSessionTemplate;
    import org.springframework.beans.factory.annotation.Qualifier;
    import org.springframework.boot.context.properties.ConfigurationProperties;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.context.annotation.Primary;
    import org.springframework.jdbc.datasource.DataSourceTransactionManager;
    
    import com.alibaba.druid.pool.DruidDataSource;
    @Configuration
    public class DataSourceConfiguration1 {
    	
    	@Bean(name = "dataSource1")
    	@Primary
    	@ConfigurationProperties(prefix = "datasource.1")
    	public DataSource dataSource() {
    		return new DruidDataSource();
    	}
    	
    	@Bean(name = "dataSourceTransactionManager1")
    	@Primary
    	public DataSourceTransactionManager dataSourceTransactionManager(@Qualifier("dataSource1")DataSource dataSource) {
    		return new DataSourceTransactionManager(dataSource);
    	}
    	
    	@Bean(name = "sqlSessionFactory1")
    	@Primary
    	public SqlSessionFactory sessionFactory(@Qualifier("dataSource1")DataSource dataSource) throws Exception {
    		SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
    		sessionFactoryBean.setDataSource(dataSource);
    		return sessionFactoryBean.getObject();
    	}
    	
    	@Bean("sqlSessionTemplate1")
    	@Primary
    	public SqlSessionTemplate sqlSessionTemplate(@Qualifier("sqlSessionFactory1") SqlSessionFactory sqlSessionFactory) {
    		return new SqlSessionTemplate(sqlSessionFactory);
    	}
    }

第二个数据源以及持久层需要的组件

package io.springboot.multidatasource.configuration;
    
    import javax.sql.DataSource;
    
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.mybatis.spring.SqlSessionFactoryBean;
    import org.mybatis.spring.SqlSessionTemplate;
    import org.springframework.beans.factory.annotation.Qualifier;
    import org.springframework.boot.context.properties.ConfigurationProperties;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.jdbc.datasource.DataSourceTransactionManager;
    
    import com.alibaba.druid.pool.DruidDataSource;
    
    @Configuration
    public class DataSourceConfiguration2 {
    	@Bean(name = "dataSource2")
    	@ConfigurationProperties(prefix = "datasource.2")
    	public DataSource dataSource() {
    		return new DruidDataSource();
    	}
    	
    	@Bean(name = "dataSourceTransactionManager2")
    	public DataSourceTransactionManager dataSourceTransactionManager(@Qualifier("dataSource2")DataSource dataSource) {
    		return new DataSourceTransactionManager(dataSource);
    	}
    	
    	@Bean(name = "sqlSessionFactory2")
    	public SqlSessionFactory sessionFactory(@Qualifier("dataSource2")DataSource dataSource) throws Exception {
    		SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
    		sessionFactoryBean.setDataSource(dataSource);
    		return sessionFactoryBean.getObject();
    	}
    	
    	@Bean("sqlSessionTemplate2")
    	public SqlSessionTemplate sqlSessionTemplate(@Qualifier("sqlSessionFactory2") SqlSessionFactory sqlSessionFactory) {
    		return new SqlSessionTemplate(sqlSessionFactory);
    	}
    }

可以看到，配置1中的bean，比配置2中的bean多了一个 `@Primary` 注解。  
当其他的组件通过@Autowired等方式注入一个类的时候。而IOC中有多个该的实现。那么标注了`@Primary` 注解的Bean会优先注入。详细可以参阅官方文档

[https://docs.spring.io/spring/docs/5.1.5.RELEASE/spring-framework-reference/core.html\#beans-autowired-annotation-primary 12][https_docs.spring.io_spring_docs_5.1.5.RELEASE_spring-framework-reference_core.html_beans-autowired-annotation-primary_12]

### Main ###

package io.springboot.multidatasource;
    
    
    import org.mybatis.spring.annotation.MapperScan;
    import org.mybatis.spring.annotation.MapperScans;
    import org.springframework.boot.SpringApplication;
    import org.springframework.boot.autoconfigure.SpringBootApplication;
    
    @SpringBootApplication
    @MapperScans(value = {
    	@MapperScan(basePackages = "io.springboot.multidatasource.mapper1",
    			sqlSessionFactoryRef = "sqlSessionFactory1",sqlSessionTemplateRef = "sqlSessionTemplate1"),
    	
    	@MapperScan(basePackages = "io.springboot.multidatasource.mapper2",
    			sqlSessionFactoryRef = "sqlSessionFactory2",sqlSessionTemplateRef = "sqlSessionTemplate2"),
    })
    public class MultidatasourceApplication {
    	public static void main(String[] args) {
    		SpringApplication.run(MultidatasourceApplication.class, args);
    	}
    }

重点在于 `@MapperScan`注解。该注解会去扫描指定包下的接口。并且动态的生成实现类。  
通过 `sqlSessionFactoryRe`f 和 `sqlSessionTemplateRef` 指定它们生成代理对象时。使用的SqlSessionFactory 和 SqlSession。（值就是定义在了IOC中的bean名称）。

### 源码 ###

[GitHub 11][GitHub_11]

### [springboot-community/multidatasource][GitHub_11] ###

Contribute to springboot-community/multidatasource development by creating an account on GitHub.

[https_docs.spring.io_spring_docs_5.1.5.RELEASE_spring-framework-reference_core.html_beans-autowired-annotation-primary_12]: https://docs.spring.io/spring/docs/5.1.5.RELEASE/spring-framework-reference/core.html#beans-autowired-annotation-primary
[GitHub_11]: https://github.com/springboot-community/multidatasource