1.接上面的事物介绍

/*** IAtom support transaction of database.* It can be invoked in Db.tx(IAtom atom) method.* <br>* Example:<br>* Db.tx(new IAtom(){<br>*        public boolean run() throws SQLException {<br>*           int result1 = Db.update("update account set cash = cash - ? where id = ?", 100, 123);<br>*           int result2 = Db.update("update account set cash = cash + ? where id = ?", 100, 456);<br>*          return result1 == 1 && result2 == 1;<br>*         }});*/

2.Db.tx他的原理呢,我这里详细介绍一下,其实非常简单

/*** Execute transaction.* @param transactionLevel the transaction level* @param atom the atom operation* @return true if transaction executing succeed otherwise false*/public  static boolean tx(int transactionLevel, IAtom atom) {Connection conn = DbKit.getThreadLocalConnection();if (conn != null) {   // Nested transaction supporttry {if (conn.getTransactionIsolation() < transactionLevel)conn.setTransactionIsolation(transactionLevel);boolean result = atom.run();if (result)return true;throw new ActiveRecordException("Nested transaction is failure.");  // important:can not return false}catch (SQLException e) {throw new ActiveRecordException(e);}}Boolean autoCommit = null;try {conn = DbKit.getDataSource().getConnection();autoCommit = conn.getAutoCommit();DbKit.setThreadLocalConnection(conn);conn.setTransactionIsolation(transactionLevel);conn.setAutoCommit(false);boolean result = atom.run();if (result)conn.commit();elseconn.rollback();return result;} catch (Exception e) {if (conn != null)try {conn.rollback();} catch (Exception e1) {e1.printStackTrace();}return false; // throw new ActiveRecordException(e);} finally {try {if (conn != null) {if (autoCommit != null)conn.setAutoCommit(autoCommit);conn.close();}} catch (Exception e) {e.printStackTrace();  // can not throw exception here, otherwise the more important exception in previous catch block can not be thrown} finally {DbKit.removeThreadLocalConnection();    // prevent memory leak}}}

3.跟我上一篇博客基本上差不多,下面就是链接
http://my.oschina.net/skyim/blog/140867
boolean result = atom.run(); 这个地方就是调用我们

int result1 = Db.update("update account set cash = cash - ? where id = ?", 100, 123);
int result2 = Db.update("update account set cash = cash + ? where id = ?", 100, 456);

4.如果返回false就回滚,返回true就提交
下一阶段我会开始写扩展ext的源码,尽情期待