mybatis源码分析二之DefaultSqlSessionFactory

DefaultSqlSessionFactory

  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
         <!-- 上面指定了数据库配置文件， 配置文件里面也是对应的这四个属性 -->
         <property name="driver" value="${driver}"/>
         <property name="url" value="${url}"/>
         <property name="username" value="${username}"/>
         <property name="password" value="${password}"/>

      </dataSource>
    </environment>
  </environments>

    /**
    核心方法，DefaultSqlSessionFactory其他方法都是调用此方法
    **/
    private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
    Transaction tx = null;
    try {
      //通过Confuguration对象去获取Mybatis相关配置信息, Environment对象包含了数据源和事务的配置(从上面的配置可以看出)
      final Environment environment = configuration.getEnvironment();
      //通过环境配置获取事务工厂，如果没有配置默认是   new ManagedTransactionFactory();
      final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
      tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
      //通过配置创建一个Executor，Executor是对jdbc中Statement的封装
      final Executor executor = configuration.newExecutor(tx, execType);
      //此处也是写死的，创建一个DefaultSqlSession对象
      return new DefaultSqlSession(configuration, executor);
    } catch (Exception e) {
      //可能已经获取了一个连接，所以此处调用close事务
      closeTransaction(tx); // may have fetched a connection so lets call close()
      throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
    } finally {
      ErrorContext.instance().reset();
    }
  }


  private TransactionFactory getTransactionFactoryFromEnvironment(Environment environment) {
    if (environment == null || environment.getTransactionFactory() == null) {
      return managedTransactionFactory;
    }
    return environment.getTransactionFactory();
  }

DefaultSqlSession

非mapper接口方式

1. 代码案例

        @Test