code: public static SqlSession getSession() throws IOException {
  		SqlSession session = (SqlSession) THREAD_SESSION.get();  
  	    try {  
  	        if (session == null) {  
  	        	session = getSessionFactory().getSession();
  	        	THREAD_SESSION.set(session);  
  	        }  
  	    } catch (Exception e) {  
  	        throw new IOException(e);  
  	    }  
  	    return session;  
  	}
docs: 获取当前线程的Sql会话
  
  @return Sql会话类
  @throws IOException IO异常处理