Mybatis source code parsing (b): SqlSession

Mybatis process:

2. Get The SqlSession

• Remove Exceutor (actuator) from the configuration file, call openSessionFromDataSource ()
  
• New types of actuators default: SIMPLE
  
• There are three types of actuators:
  
• note:
  

	executor = (Executor) interceptorChain.pluginAll(executor);

Executor to intercept enhanced design patterns used here was the decorator pattern

• Then return: DefaultSqlSession (configuratioin, Executor, affairs issues)
  Executor execution of CRUD configuratioin

Summary: The process of obtaining the SqlSession

• First SqlSessionFactory call openSession ()

  SqlSession session = sessionFactory.openSession();
  

• Then openSession () call openSessionFromDataSource ()

   @Override
  public SqlSession openSession() {
    return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, false);
  }
  

• Return DefaultSqlSession objects , note DefaultSqlSession include: (the Configuration, Executor, affairs)

  private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
  Transaction tx = null;
  try {
    final Environment environment = configuration.getEnvironment();
    final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
    tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
    //创建一个新的执行器，类型为execType
    final Executor executor = configuration.newExecutor(tx, execType);
    return new DefaultSqlSession(configuration, executor, autoCommit);
  } catch (Exception e) {
    closeTransaction(tx); // may have fetched a connection so lets call close()
    throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
  } finally {
    ErrorContext.instance().reset();
  }
  }