问题描述
今天花了一天时间解决一个问题,好久没有这样钻研解决这样的问题了。
http://topic.csdn.net/t/20050608/16/4068615.html
问题跟这个帖子相同,就是使用proxool+sybase处理事务时,会报错。
先看看以下代码
public static void test2() throws Exception { // Connection conn = getConnectionFromPool(); Connection conn = getConnection(); conn.setAutoCommit(false); Statement stmt = conn.createStatement(); String sql = "select 1"; stmt.executeQuery(sql); conn.commit(); try { conn.setAutoCommit(true); } catch (Exception e) { e.printStackTrace(); } stmt.close(); conn.close(); } public static Connection getConnection() throws Exception { Class.forName("com.sybase.jdbc3.jdbc.SybDriver"); String username = "sa"; String pwd = ""; String url = "jdbc:sybase:Tds:192.168.0.100:5000/test"; return DriverManager.getConnection(url, username, pwd); } static public Connection getConnectionFromPool() throws Exception { Connection connection = null; String alias = "test"; Class.forName("org.logicalcobwebs.proxool.ProxoolDriver"); if (connection == null) { Properties info = new Properties(); info.setProperty("proxool.maximum-connection-count", "20"); info.setProperty("user", "sa"); info.setProperty("password", ""); info.put("proxool.maximum-active-time", "60000"); String driverClass = "com.sybase.jdbc3.jdbc.SybDriver"; String driverUrl = "jdbc:sybase:Tds:192.168.0.100:5000/test"; String url = "proxool." + alias + ":" + driverClass + ":" + driverUrl; connection = DriverManager.getConnection(url, info); System.out.println(connection); } return connection; }
在运行test2()函数时没有出现异常正常,这里是没有使用proxool,用原始的数据库连接方式。
将test2()第一行的注释去掉,将第二行注释掉,运行时就会报错
Exception in thread "main" com.sybase.jdbc3.jdbc.SybSQLException: SET CHAINED command not allowed within multi-statement transaction. at com.sybase.jdbc3.tds.Tds.processEed(Tds.java:2942) at com.sybase.jdbc3.tds.Tds.nextResult(Tds.java:2246) at com.sybase.jdbc3.jdbc.ResultGetter.nextResult(ResultGetter.java:69) at com.sybase.jdbc3.jdbc.SybStatement.nextResult(SybStatement.java:220) at com.sybase.jdbc3.jdbc.SybStatement.nextResult(SybStatement.java:203) at com.sybase.jdbc3.jdbc.SybStatement.updateLoop(SybStatement.java:1804) at com.sybase.jdbc3.jdbc.SybStatement.executeUpdate(SybStatement.java:1787) at com.sybase.jdbc3.jdbc.SybPreparedStatement.executeUpdate(SybPreparedStatement.java:116) at com.sybase.jdbc3.tds.Tds.setOption(Tds.java:1278) at com.sybase.jdbc3.jdbc.SybConnection.setAutoCommit(SybConnection.java:1011) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at org.logicalcobwebs.proxool.WrappedConnection.invoke(WrappedConnection.java:208) at org.logicalcobwebs.proxool.WrappedConnection.intercept(WrappedConnection.java:98) at com.sybase.jdbcx.SybConnection$$EnhancerByProxool$$8df5facc.setAutoCommit(<generated>) at TestConnectionTran.test(TestConnectionTran.java:34) at TestConnectionTran.main(TestConnectionTran.java:13)
问题原因
s_phoenix大侠的解决办法是:
修改的是proxool,因为jconn没有源代码。修改hibernate又不成功,只好修改夹在其中的缓冲池了。
虽然我最后也是这样解决的,但是s_phoenix大侠没有告诉我怎么修改,我还是花了几个小时来调试proxool源代码。
首先说明下,sybase为什么会报这个错误
SET CHAINED command not allowed within multi-statement transaction.
到google,baidu里面随便搜下,就有一堆。简单的一句话:处于事务环境下,调用 set chained 是会发生异常的,这一点手册上也非常明确的指出了。使用sybase的jconn驱动,调用setAutoCommit(false)事务开始,也就是 set chained on,然后执行完相应的操作后commit或者rollback结束事务,这时需要setAutoCommit(true)“完壁归赵”,以便连接池回收。但是在proxool中后面setAutoCommit(true)会报错,以上的错误。这个错误明显是事务没有结束又调用setAutoCommit方法,但是明明事务已经结束了,原因何在?
查看源代码发现了问题,先看源代码org.logicalcobwebs.proxool.WrappedConnection:
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Object result = null; int argCount = args != null ? args.length : 0; Method concreteMethod = method; if (proxyConnection != null && proxyConnection.getConnection() != null) { concreteMethod = InvokerFacade.getConcreteMethod(proxyConnection.getConnection().getClass(), method); } try { if (proxyConnection != null && proxyConnection.isReallyClosed()) { // The user is trying to do something to this connection and it's been closed. ................ if (concreteMethod.getName().equals(IS_CLOSED_METHOD)) { return result; }
这块代码是动态代理执行Connection的所有方式时被调用的方法,可以看出,每次都会调用proxyConnection.isReallyClosed()方法,这个方法里面调用的是Connection.isClose()方法.使用连接池调用test2()函数,可以类比于以下方式:
public static void test1() throws Exception { Connection conn = getConnection(); conn.isClosed(); conn.setAutoCommit(false); conn.isClosed(); conn.commit(); conn.isClosed(); conn.setAutoCommit(true); }
运行test1报错根test2一样.问题就出现在这里.可以猜到conn.isClosed();又开启了一个新的事务,该事务没有结束就conn.setAutoCommit(true);当然会报错.事实上,我通过抓报工具,发现conn.isClosed();会发送命令sp_mda到数据库中,这个过程就可以看作是在数据库中执行以下命令:
set chained on go select 1 go commit go sp_mda 0,3,2 set chained off go
问题 解决
问题原因找到了,怎么解决呢? s_phoenix大侠给了我提示,提前拦截setAutoCommit方法.
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { Object result = null; int argCount = args != null ? args.length : 0; Method concreteMethod = method; if (proxyConnection != null && proxyConnection.getConnection() != null) { concreteMethod = InvokerFacade.getConcreteMethod(proxyConnection .getConnection().getClass(), method); } try { if (concreteMethod.getName().equals("setAutoCommit")) { result = concreteMethod.invoke(proxyConnection.getConnection(), args); return result; } } catch (Exception e) { LOG.error("setAutoCommit error", e); throw e; } try { if (proxyConnection != null && proxyConnection.isReallyClosed()) { // The user is trying to do something to this connection and // it's been closed. if (concreteMethod.getName().equals(IS_CLOSED_METHOD)) { // That's cool. No problem checking as many times as you // like.
简单的测试了下,没有问题.会不会对其他地方产生影响呢?我不知道,可能会发生很奇妙的结果,哈哈...还是得严格测试下.
修改后,还要注意一点,在commit后面要紧跟setAutoCommit(true),如果中间又调用connection其他方法,还是会报错的.