springboot+mybatis解决多数据源切换事务控制不生效的问题

网上好多的springboot的事务都是瞎扯，根本不起作用，后来通过各种渠道查证，springboot的生命式事务需要重写Transaction。

追溯源代码：

        查看源代码中DataSourceTransactionManager这个类

       当我们配置了事物管理器和拦截Service中的方法后，每次执行Service中方法前会开启一个事务，并且同时会缓存一些东西：DataSource、SqlSessionFactory、Connection等，所以，我们在外面再怎么设置要求切换数据源也没用，因为Conneciton都是从缓存中拿的，所以我们要想能够顺利的切换数据源，实际就是能够动态的根据DatabaseType获取不同的Connection，并且要求不能影响整个事物的特性。

主要是两个类：

1、MultiDataSourceTransaction：

package com.youjia.user.config.ds.transcation;

import com.alibaba.druid.support.logging.Log;
import com.alibaba.druid.support.logging.LogFactory;
import org.apache.ibatis.transaction.Transaction;
import org.springframework.jdbc.CannotGetJdbcConnectionException;
import org.springframework.jdbc.datasource.DataSourceUtils;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import static org.apache.commons.lang3.Validate.notNull;

/**
 * 
多数据源切换，支持事务
 *
 * @author 高仕立
 * @date 2018/2/6 9:09
 * @since
 */
public class MultiDataSourceTransaction implements Transaction{
    private static final Log LOGGER = LogFactory.getLog(MultiDataSourceTransaction.class);

    private final DataSource dataSource;

    private Connection mainConnection;

    private String mainDatabaseIdentification;

    private ConcurrentMap otherConnectionMap;


    private boolean isConnectionTransactional;

    private boolean autoCommit;


    public MultiDataSourceTransaction(DataSource dataSource) {
        notNull(dataSource, "No DataSource specified");
        this.dataSource = dataSource;
        otherConnectionMap = new ConcurrentHashMap<>();
        mainDatabaseIdentification=DataSourceContextHolder.getReadOrWrite();
    }


    /**
     * {@inheritDoc}
     */
    @Override
    public Connection getConnection() throws SQLException {
        String databaseIdentification = DataSourceContextHolder.getReadOrWrite();
        if (databaseIdentification.equals(mainDatabaseIdentification)) {
            if (mainConnection != null) return mainConnection;
            else {
                openMainConnection();
                mainDatabaseIdentification =databaseIdentification;
                return mainConnection;
            }
        } else {
            if (!otherConnectionMap.containsKey(databaseIdentification)) {
                try {
                    Connection conn = dataSource.getConnection();
                    otherConnectionMap.put(databaseIdentification, conn);
                } catch (SQLException ex) {
                    throw new CannotGetJdbcConnectionException("Could not get JDBC Connection", ex);
                }
            }
            return otherConnectionMap.get(databaseIdentification);
        }

    }


    private void openMainConnection() throws SQLException {
        this.mainConnection = DataSourceUtils.getConnection(this.dataSource);
        this.autoCommit = this.mainConnection.getAutoCommit();
        this.isConnectionTransactional = DataSourceUtils.isConnectionTransactional(this.mainConnection, this.dataSource);

        if (LOGGER.isDebugEnabled()) {
            LOGGER.debug(
                    "JDBC Connection ["
                            + this.mainConnection
                            + "] will"
                            + (this.isConnectionTransactional ? " " : " not ")
                            + "be managed by Spring");
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void commit() throws SQLException {
        if (this.mainConnection != null && !this.isConnectionTransactional && !this.autoCommit) {
            if (LOGGER.isDebugEnabled()) {
                LOGGER.debug("Committing JDBC Connection [" + this.mainConnection + "]");
            }
            this.mainConnection.commit();
            for (Connection connection : otherConnectionMap.values()) {
                connection.commit();
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void rollback() throws SQLException {
        if (this.mainConnection != null && !this.isConnectionTransactional && !this.autoCommit) {
            if (LOGGER.isDebugEnabled()) {
                LOGGER.debug("Rolling back JDBC Connection [" + this.mainConnection + "]");
            }
            this.mainConnection.rollback();
            for (Connection connection : otherConnectionMap.values()) {
                connection.rollback();
            }
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void close() throws SQLException {
        DataSourceUtils.releaseConnection(this.mainConnection, this.dataSource);
        for (Connection connection : otherConnectionMap.values()) {
            DataSourceUtils.releaseConnection(connection, this.dataSource);
        }
    }

    @Override
    public Integer getTimeout() throws SQLException {
        return null;
    }
}

2、MultiDataSourceTransactionFactory：

package com.youjia.user.config.ds.transcation;

import org.apache.ibatis.session.TransactionIsolationLevel;
import org.apache.ibatis.transaction.Transaction;
import org.mybatis.spring.transaction.SpringManagedTransactionFactory;

import javax.sql.DataSource;

/**
 * 
支持Service内多数据源切换的Factory
 *
 * @author 高仕立
 * @date 2018/2/6 9:18
 * @since
 */
public class MultiDataSourceTransactionFactory extends SpringManagedTransactionFactory {
    @Override
    public Transaction newTransaction(DataSource dataSource, TransactionIsolationLevel level, boolean autoCommit) {
        return new MultiDataSourceTransaction(dataSource);
    }
}

3、最后在mybatis的配置中加入这个sessionFactory：

/**
     * 配置sqlSessionFactory
     *
     * @return SqlSessionFactory对象
     * @throws Exception
     */
    @Bean(name="sqlSessionFactory")
    public SqlSessionFactory sqlSessionFactorys() throws Exception {
        log.info("--------------------  sqlSessionFactory init ---------------------");
        try {
            SqlSessionFactoryBean sessionFactoryBean = new SqlSessionFactoryBean();
            sessionFactoryBean.setDataSource(roundRobinDataSouceProxy());
            sessionFactoryBean.setTransactionFactory(new MultiDataSourceTransactionFactory());
            // 读取配置 
            sessionFactoryBean.setTypeAliasesPackage("com.youjia.user.model");
            
            //设置mapper.xml文件所在位置 
            Resource[] resources = new PathMatchingResourcePatternResolver().getResources(MAPPER_LOCATION);
            sessionFactoryBean.setMapperLocations(resources);
            return sessionFactoryBean.getObject();
        } catch (IOException e) {
            log.error("mybatis resolver mapper*xml is error",e);
            return null;
        } catch (Exception e) {
            log.error("mybatis sqlSessionFactoryBean create error",e);
            return null;
        }
    }

4、最后在代码中引入

@Transactional(propagation = Propagation.REQUIRED, rollbackFor = Throwable.class)

需要注意的是：

        在spring的文档中说道，spring声明式事务管理默认对非检查型异常和运行时异常进行事务回滚，而对检查型异常（try catch）则不进行回滚操作：

        故而如果异常被try｛｝catch｛｝了，事务就不回滚了，如果想让事务回滚必须再往外抛try｛｝catch｛throw Exception｝。