mybatis0090-SqlSessionFactory创建SqlSession

文章目录

1. 创建SqlSession2. DefaultSqlSessionFactory的openSessionFromDataSource3. 执行流程

1. 创建SqlSession

SqlSession sqlSession = sqlSessionFactory.openSession();

2. DefaultSqlSessionFactory的openSessionFromDataSource

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); 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(); } }

创建SqlSession的过程，其实是对jdbc的Connection的一次再封装，Connection–>Statement–>Executor–>SqlSeesion Executor有三种类型：SIMPLE 就是普通的执行器；REUSE 执行器会重用预处理语句（prepared statements）； BATCH 执行器将重用语句并执行批量更新。configuration.newExecutor(tx, execType)会根据execType创建出其中一种执行器(默认是ExecutorType.SIMPLE)，如下：

public Executor newExecutor(Transaction transaction, ExecutorType executorType) { executorType = executorType == null ? defaultExecutorType : executorType; executorType = executorType == null ? ExecutorType.SIMPLE : executorType; Executor executor; if (ExecutorType.BATCH == executorType) { executor = new BatchExecutor(this, transaction); } else if (ExecutorType.REUSE == executorType) { executor = new ReuseExecutor(this, transaction); } else { executor = new SimpleExecutor(this, transaction); } if (cacheEnabled) { executor = new CachingExecutor(executor); } executor = (Executor) interceptorChain.pluginAll(executor); return executor; }

最后，将执行器和配置对象封装到SqlSession中返回，所以对于使用mybatis把SqlSession当作Connection来使用即可。

3. 执行流程