Mybatis事务（三）事务工厂

在前面一篇博客Mybatis事务（一）事务管理方式中我们提到，mybatis及spring提供了三个事务实现类：JdbcTransaction、ManagedTransaction和SpringManagedTransaction三个事务实现类，同时Mybatis也很友好的给我们提供了对应事务类的生成工厂。

TransactionFactory接口：提供的主要接口是newTransaction（），根据数据库连接Connection来创建事务，源码如下：

//事务工厂接口
public interface TransactionFactory {

  /**
   * Sets transaction factory custom properties.
   * @param props
   */
  //配置工厂属性
  void setProperties(Properties props);

  /**
   * Creates a {@link Transaction} out of an existing connection.
   * @param conn Existing database connection
   * @return Transaction
   * @since 3.1.0
   */
  //通过Connection获得事务
  Transaction newTransaction(Connection conn);

  /**
   * Creates a {@link Transaction} out of a datasource.
   * @param dataSource DataSource to take the connection from
   * @param level Desired isolation level
   * @param autoCommit Desired autocommit
   * @return Transaction
   * @since 3.1.0
   */
  //通过数据库，事务等级及事务是否自动提交创建事务
  Transaction newTransaction(DataSource dataSource, TransactionIsolationLevel level, boolean autoCommit);

}

JdbcTransactionFactory：创建JdbcTransaction事务，源码如下：

public class JdbcTransactionFactory implements TransactionFactory {

  @Override
  public void setProperties(Properties props) {
  }

  @Override
  public Transaction newTransaction(Connection conn) {
	//创建JDBC事务
    return new JdbcTransaction(conn);
  }

  @Override
  public Transaction newTransaction(DataSource ds, TransactionIsolationLevel level, boolean autoCommit) {
    return new JdbcTransaction(ds, level, autoCommit);
  }
}

ManagedTransactionFactory：创建ManagedTransaction事务，源码如下：

public class ManagedTransactionFactory implements TransactionFactory {

  private boolean closeConnection = true;

  @Override
  public void setProperties(Properties props) {
    if (props != null) {
      String closeConnectionProperty = props.getProperty("closeConnection");
      if (closeConnectionProperty != null) {
        closeConnection = Boolean.valueOf(closeConnectionProperty);
      }
    }
  }

  @Override
  public Transaction newTransaction(Connection conn) {
	//创建MANAGED事务
    return new ManagedTransaction(conn, closeConnection);
  }

  @Override
  public Transaction newTransaction(DataSource ds, TransactionIsolationLevel level, boolean autoCommit) {
    // Silently ignores autocommit and isolation level, as managed transactions are entirely
    // controlled by an external manager.  It's silently ignored so that
    // code remains portable between managed and unmanaged configurations.
    return new ManagedTransaction(ds, level, closeConnection);
  }
}

SpringManagedTransactionFactory：创建SpringManagedTransaction，源码如下：

public class SpringManagedTransactionFactory implements TransactionFactory {

  /**
   * {@inheritDoc}
   */
  @Override
  public Transaction newTransaction(DataSource dataSource, TransactionIsolationLevel level, boolean autoCommit) {
	//spring 通过DataSource创建事务
    return new SpringManagedTransaction(dataSource);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public Transaction newTransaction(Connection conn) {
	//无法通过connection创建事务
    throw new UnsupportedOperationException("New Spring transactions require a DataSource");
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public void setProperties(Properties props) {
    // not needed in this version
  }

}

Mybatis提供了简单有效的事务生产工厂