public Connection getConnection() {
    return DataSourceUtils.getConnection(dataSources.get(getDataSourceName()));
  }
Returns the {@link Connection} associated with the current {@link Thread}.
Can be called only after {@link #bindDataSource(String)} and before {@link #unbindDataSource()}.
Ensures that the same instance is returned all the time.
@throws IllegalStateException Thrown when there is no bound {@link DataSource}.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/txn/jdbc/MultiDataSourceJdbcResource.java