How to create a scrollable ResultSet?

问题:

I got this simple code to retrieve a recordset from a MSSQL Server 2008 which has to be scrollable due to the fact that I set the ResultSet.TYPE_SCROLL_INSENSITVE, same as the example from the Javadocs:

String qry = "SELECT * from tblPeople";
SQLConnection sql = new SQLConnection();
Statement stmt = sql.getConnection().createStatement(
                                        ResultSet.TYPE_SCROLL_INSENSITIVE,
                                        ResultSet.CONCUR_UPDATABLE);
ResultSet rs = stmt.executeQuery(qry);

Unfortunately I still got this Stack Trace when I want to get the row count like rs.last(); int rowCount = rs.getRow();:

java.sql.SQLException: ResultSet may only be accessed in a forward direction.
    at net.sourceforge.jtds.jdbc.JtdsResultSet.checkScrollable(JtdsResultSet.java:304)
    at net.sourceforge.jtds.jdbc.JtdsResultSet.last(JtdsResultSet.java:551)
    at test.personen.Main.main(Main.java:44)

Why is that and how can I fix it (by the way, when I check the Type of the ResultSet, I get 1003..)?

回答1:

Most likely the combination of TYPE_SCROLL_INSENSITIVE is not compatible with CONCUR_UPDATABLE. According to the JDBC specification, a driver is free to downgrade a ResultSet if it can't service the requested scrollability and/or concurrency mode. See also: http://jtds.sourceforge.net/resultSets.html :

TYPE_SCROLL_INSENSITIVE | Static cursor | Heavy | Only works with read-only concurrency (updatable is downgraded). SQL Server generates a temporary table, so changes made by others are not visible. Scrollable.

Which confirms that the driver will downgrade when specifying CONCUR_UPDATABLE.

You might want to consider using TYPE_SCROLL_SENSITIVE or simply not combine scrollability with updatability.

回答2:

jTDS TYPE_SCROLL_INSENSITIVE only supports the read-only operations.

Change ResultSet.TYPE_SCROLL_INSENSITIVE to ResultSet.TYPE_SCROLL_SENSITIVE

See http://www.anyang-window.com.cn/jtds-on-the-database-connection-resultset-is-read-only/