MySQLNonTransientConnectionException: No operations allowed after connection closed
2016-10-10 00:00
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MySQLNonTransientConnectionException: No operations allowed after statement closed
之所以会出现这个异常,是因为MySQL在5以后针对超长时间DB连接做了一个处理,那就是如果一个DB连接在无任何操作情况下过了8个小时后,Mysql会自动把这个连接关闭。所以使用连接池的时候虽然连接对象还在但是链接数据库的时候会一直报这个异常。解决方法很简单在Mysql的官方网站上就可以找到。
查看了Mysql的文档,以及Connector/J的文档以及在线说明发现,出现这种异常的原因是:
Mysql服务器默认的“wait_timeout”是8小时,也就是说一个connection空闲超过8个小时,Mysql将自动断开该connection。这就是问题的所在,在C3P0 pools中的connections如果空闲超过8小时,Mysql将其断开,而C3P0并不知道该connection已经失效,如果这时有Client请求connection,C3P0将该失效的Connection提供给Client,将会造成上面的异常。
解决的方法有3种:
增加wait_timeout的时间。
减少Connection pools中connection的lifetime。
测试Connection pools中connection的有效性。
有两个方法,
jdbc:mysql://localhost:3306/makhtutat?autoReconnect=true
不过Mysql并不建议使用这个方法。因为第一个DB操作失败的后,第二DB成功前如果出现了重新连接的效果。这个失败操作将不会处于一个事务以内,第二DB操作如果成功的话,这个事务将被提交。
当然如果出现了重新连接,一些用户变量和临时表的信息也会丢失。
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
int retryCount = 5;
boolean transactionCompleted = false;
do {
try {
conn = getConnection(); // assume getting this from a
// javax.sql.DataSource, or the
// java.sql.DriverManager
conn.setAutoCommit(false);
retryCount = 0;
stmt = conn.createStatement();
String query = "SELECT foo FROM bar ORDER BY baz";
rs = stmt.executeQuery(query);
while (rs.next()) {
}
all.close()
transactionCompleted = true;
} catch (SQLException sqlEx) {
String sqlState = sqlEx.getSQLState();
// 这个08S01就是这个异常的sql状态。单独处理手动重新链接就可以了。
if ("08S01".equals(sqlState) || "40001".equals(sqlState))
{
retryCount--;
} else {
retryCount = 0;
}
} finally {
all close:
}
} while (!transactionCompleted && (retryCount > 0));}
}</span>
之所以会出现这个异常,是因为MySQL在5以后针对超长时间DB连接做了一个处理,那就是如果一个DB连接在无任何操作情况下过了8个小时后,Mysql会自动把这个连接关闭。所以使用连接池的时候虽然连接对象还在但是链接数据库的时候会一直报这个异常。解决方法很简单在Mysql的官方网站上就可以找到。
查看了Mysql的文档,以及Connector/J的文档以及在线说明发现,出现这种异常的原因是:
Mysql服务器默认的“wait_timeout”是8小时,也就是说一个connection空闲超过8个小时,Mysql将自动断开该connection。这就是问题的所在,在C3P0 pools中的connections如果空闲超过8小时,Mysql将其断开,而C3P0并不知道该connection已经失效,如果这时有Client请求connection,C3P0将该失效的Connection提供给Client,将会造成上面的异常。
解决的方法有3种:
增加wait_timeout的时间。
减少Connection pools中connection的lifetime。
测试Connection pools中connection的有效性。
有两个方法,
第一种是在DB连接字符串后面加一个参数。
这样的话,如果当前链接因为超时断掉了,那么驱动程序会自动重新连接数据库。jdbc:mysql://localhost:3306/makhtutat?autoReconnect=true
不过Mysql并不建议使用这个方法。因为第一个DB操作失败的后,第二DB成功前如果出现了重新连接的效果。这个失败操作将不会处于一个事务以内,第二DB操作如果成功的话,这个事务将被提交。
conn.createStatement().execute( "UPDATE checking_account SET balance = balance - 1000.00 WHERE customer='Smith'"); conn.createStatement().execute( "UPDATE savings_account SET balance = balance + 1000.00 WHERE customer='Smith'"); conn.commit();
当然如果出现了重新连接,一些用户变量和临时表的信息也会丢失。
另一种方法是Mysql推荐的,需要程序员手动处理异常。
<span style="font-family:Microsoft YaHei;font-size:12px;">public void doBusinessOp() throws SQLException {Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
int retryCount = 5;
boolean transactionCompleted = false;
do {
try {
conn = getConnection(); // assume getting this from a
// javax.sql.DataSource, or the
// java.sql.DriverManager
conn.setAutoCommit(false);
retryCount = 0;
stmt = conn.createStatement();
String query = "SELECT foo FROM bar ORDER BY baz";
rs = stmt.executeQuery(query);
while (rs.next()) {
}
all.close()
transactionCompleted = true;
} catch (SQLException sqlEx) {
String sqlState = sqlEx.getSQLState();
// 这个08S01就是这个异常的sql状态。单独处理手动重新链接就可以了。
if ("08S01".equals(sqlState) || "40001".equals(sqlState))
{
retryCount--;
} else {
retryCount = 0;
}
} finally {
all close:
}
} while (!transactionCompleted && (retryCount > 0));}
}</span>
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