JDBC Microsoft SQL timeout not fired

Question

I am using sqljdbc4.jar for connection from my application to SQL Server via wifi. The connection works fine and queries too, but sometimes the wifi falls and I need to react - try to reconnect and then inform the user about a connection fail.

The issue is, even when I set query timeout, the execution hangs in case of disconnection and no SqlTimeoutException is fired.

The connection (username and psw deleted):

SQLconnection = DriverManager.getConnection("jdbc:sqlserver://%address%;user=%UserName%;password=%password%;database=%db_name%");

SQLSelectStatement = SQLconnection.createStatement();
SQLSelectStatement.setQueryTimeout(2);

Execution of query:

String sql = "%my query%";
ResultSet rs;
try {
    rs = SQLSelectStatement.executeQuery(sql);
} catch (SQLException sqle) {
    ConnectSQL(); //try to connect again
    rs = SQLSelectStatement.executeQuery(sql);
}

If the method throws a SQLException , I'll inform the user and continue. But the exception is never thrown, even in the case of connection lost.

What can I do to resolve this? I tried setting lock-timeout and logintimeout in connection string based on MSDN , method SQLconnection.setNetworkTimeout fires error too (if I understand it right, it is not implemented in microsoft driver).

The last solution I can think of is to implement some kind of timeout on my own, which will stop the query thread after a certain time. But I don't wont to reinvent the wheel.

Answer 1

Based on my googling and reading, setQueryTimeout is useful only for limitting of query execution time, not for detecting of connection error.

I have found this great article describing timeouts in JDBC drivers. All I needed was to hit socketTimeout which is not supported in MS JDBC driver.

I switched to jTDS driver and rewrited my code a bit. Now it works as I expected.

//initialize SQL connection
    try {
        Class.forName("net.sourceforge.jtds.jdbc.Driver");
    } catch (ClassNotFoundException ex) {
        Cls_log.LogError(ex);
    }

private void ConnectSQL() {
    try {
        String url = "jdbc:jtds:sqlserver://<ip_address>/<db_name>;instance=<SQLserver_name>;loginTimeout=5;socketTimeout=2";
        SQLconnection = DriverManager.getConnection(url, <userName>, <password>);
        SQLSelectStatement = SQLconnection.createStatement();
    } catch (SQLException ex) {
        Cls_log.LogError(ex);
    }
}

Executing my query

String sql = "%my query%";
ResultSet rs;
try {
    rs = SQLSelectStatement.executeQuery(sql);
} catch (SQLException sqle) {
    ConnectSQL(); //try to connect again
    rs = SQLSelectStatement.executeQuery(sql);
}

If this throws SQLException, I inform user and offer workaround.

Answer 2

此外，最新的Microsoft驱动程序也支持它： https : //github.com/Microsoft/mssql-jdbc/pull/85/files