Mybaits源码分析八之sqlSessiion的openSession方法

1  //通过sqlSessionFactory创建SqlSession
2     public static SqlSession getSession(){
3         return sqlSessionFactory.openSession();
4     }

1   @Override
2   public SqlSession openSession(boolean autoCommit) {
3     return openSessionFromDataSource(configuration.getDefaultExecutorType(), null, autoCommit);
4   }

 1   private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
 2     Transaction tx = null;
 3     try {
 4      //获取environment对象，就是mybatis配置中的environment子节点下的配置内容
 5       final Environment environment = configuration.getEnvironment();
 6      //构建事务工厂
 7       final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment);
 8     //创建事务实例
 9       tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);
10     //创建一个执行器
11       final Executor executor = configuration.newExecutor(tx, execType);
12      //返回默认的sqlSession
13       return new DefaultSqlSession(configuration, executor, autoCommit);
14     } catch (Exception e) {
15       closeTransaction(tx); // may have fetched a connection so lets call close()
16       throw ExceptionFactory.wrapException("Error opening session.  Cause: " + e, e);
17     } finally {
18       ErrorContext.instance().reset();
19     }
20   }

 1 public Executor newExecutor(Transaction transaction, ExecutorType executorType) {
 2     //获取默认的执行器类型，默认为SIMPLE
 3     executorType = executorType == null ? defaultExecutorType : executorType;
 4     executorType = executorType == null ? ExecutorType.SIMPLE : executorType;
 5     Executor executor;
 6    //执行器类型为三种BATCH 批量执行已经预编译的sql，REUSE 重复执行sql，SIMPLE只执行一次
 7     if (ExecutorType.BATCH == executorType) {
 8       executor = new BatchExecutor(this, transaction);
 9     } else if (ExecutorType.REUSE == executorType) {
10       executor = new ReuseExecutor(this, transaction);
11     } else {
12       executor = new SimpleExecutor(this, transaction);
13     }
14     //判断是否开启缓存，默认是开启的
15     if (cacheEnabled) {
16       executor = new CachingExecutor(executor);
17     }
18     executor = (Executor) interceptorChain.pluginAll(executor);
19     return executor;
20   }