应用场景：双数据源，就是某些项目会涉及到两个数据源或者两个以上的数据源，这个多数据源的项目一般是数据同步，也就是把数据从另一个系统中，保存到另一个系统，两边的 数据库又不一样，比如一个Mysql、一个Sql Server。但是不管是什么类型的数据库，我们都不管，直接连接就是。
为什么要使用分布式事务：顾名思义，事务就是回滚，比如如果一个在保存数据的时候，在A数据库已经 保存，但是在保存数据在B的过程抛出异常，那么是不是应该全部回滚，把已经 保存了的A、B数据库的数据全部回滚？答案是确定的。下面就解说：
pom.xml主要依赖：
<dependency><groupId>tk.mybatis</groupId><artifactId>mapper-spring-boot-starter</artifactId><version>2.0.0</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-jta-atomikos</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><scope>runtime</scope></dependency><dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId><version>1.1.10</version></dependency>
properties配置文件：
#数据源一
spring.datasource.primary.url=jdbc:mysql://localhost:3306/testspring.datasource.primary.username=rootspring.datasource.primary.password=rootspring.datasource.primary.driver-class-name=com.mysql.jdbc.Driverspring.datasource.primary.xa-data-source-class-name=com.alibaba.druid.pool.xa.DruidXADataSource
#数据源二spring.datasource.secondary.url=jdbc:mysql://localhost:3306/test1spring.datasource.secondary.username=rootspring.datasource.secondary.password=rootspring.datasource.secondary.driver-class-name=com.mysql.jdbc.Driverspring.datasource.secondary.xa-data-source-class-name=com.alibaba.druid.pool.xa.DruidXADataSource
数据源的配置类：DataSourceConfig.class
import com.alibaba.druid.pool.xa.DruidXADataSource;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;@Configuration
public class DataSourceConfig {//这里一定要加主数据源的注解@Primary@Bean(name = "primaryProperty")@ConfigurationProperties(prefix = "spring.datasource.primary")public DruidXADataSource primaryDataSource() {return new DruidXADataSource();}
//这里是第二个数据源@Bean(name = "secondaryProperty")@ConfigurationProperties(prefix = "spring.datasource.secondary")public DruidXADataSource secondaryDataSource() {return new DruidXADataSource();}
}
再分别配置他们的数据源：以便包扫描、事务交给jta-atomikos统一管理
主数据源配置类：
import com.alibaba.druid.pool.xa.DruidXADataSource;
import com.atomikos.jdbc.AtomikosDataSourceBean;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.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;import javax.sql.DataSource;import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import tk.mybatis.spring.annotation.MapperScan;@Configuration
@MapperScan(basePackages = {"com.example.dao.primary"}, sqlSessionTemplateRef = "primarySqlSessionTemplate")
public class PrimaryDBConfig {@Bean(name = "primaryDataSource")public DataSource dataSourceCar(@Qualifier("primaryProperty") DruidXADataSource druidXADataSource) {AtomikosDataSourceBean xaDataSource = new AtomikosDataSourceBean();xaDataSource.setXaDataSource(druidXADataSource);xaDataSource.setUniqueResourceName("primaryDataSource");return xaDataSource;}@Bean(name = "primarySqlSessionFactory")public SqlSessionFactory sqlSessionFactory(@Qualifier("primaryDataSource") DataSource dataSource)throws Exception {SqlSessionFactoryBean bean = new SqlSessionFactoryBean();bean.setDataSource(dataSource);bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/primary/*Mapper.xml"));//扫描指定目录的xmlreturn bean.getObject();}@Bean(name = "primarySqlSessionTemplate")public SqlSessionTemplate sqlSessionTemplate(@Qualifier("primarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {return new SqlSessionTemplate(sqlSessionFactory);}
}
同理，第二个数据源的配置SecondaryDBConfig.java
@Configuration
@MapperScan(basePackages = {"com.example.dao.secondary"}, sqlSessionTemplateRef = "secondarySqlSessionTemplate")
public class SecondaryDBConfig {@Bean(name = "secondaryDataSource")public DataSource dataSourceCar(@Qualifier("secondaryProperty") DruidXADataSource druidXADataSource) {AtomikosDataSourceBean xaDataSource = new AtomikosDataSourceBean();xaDataSource.setXaDataSource(druidXADataSource);xaDataSource.setUniqueResourceName("secondaryDataSource");return xaDataSource;}@Bean(name = "secondarySqlSessionFactory")public SqlSessionFactory sqlSessionFactory(@Qualifier("secondaryDataSource") DataSource dataSource)throws Exception {SqlSessionFactoryBean bean = new SqlSessionFactoryBean();bean.setDataSource(dataSource);bean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/secondary/*Mapper.xml"));//扫描指定目录的xmlreturn bean.getObject();}@Bean(name = "secondarySqlSessionTemplate")public SqlSessionTemplate sqlSessionTemplate(@Qualifier("secondarySqlSessionFactory") SqlSessionFactory sqlSessionFactory) throws Exception {return new SqlSessionTemplate(sqlSessionFactory);}
}
最后我们还需要配置事务管理的配置类：TransactionManagerConfig.java，以便把数据源一，数据源二全部交给jta-atomikos管理，实现分布式事务管理：
import com.atomikos.icatch.jta.UserTransactionImp;
import com.atomikos.icatch.jta.UserTransactionManager;import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.DependsOn;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.jta.JtaTransactionManager;import javax.transaction.TransactionManager;
import javax.transaction.UserTransaction;@Configuration
public class TransactionManagerConfig {@Bean(name = "userTransaction")public UserTransaction userTransaction() throws Throwable {UserTransactionImp userTransactionImp = new UserTransactionImp();userTransactionImp.setTransactionTimeout(10000);return userTransactionImp;}@Bean(name = "atomikosTransactionManager")public TransactionManager atomikosTransactionManager() throws Throwable {UserTransactionManager userTransactionManager = new UserTransactionManager();userTransactionManager.setForceShutdown(false);return userTransactionManager;}@Bean(name = "transactionManager")@DependsOn({ "userTransaction", "atomikosTransactionManager" })public PlatformTransactionManager transactionManager() throws Throwable {return new JtaTransactionManager(userTransaction(),atomikosTransactionManager());}
}
最后我们在service类上加上注解：@Transactional(value = "transactionManager", rollbackFor = Exception.class)
当value = "transactionManager"，则是分布式事务的管理。至此，全部完成。
gitHub完整项目下载地址：https://gitee.com/qhThomas/springboot-mybatis-duria.git
