如何创建可滚动的ResultSet? [英] How to create a scrollable ResultSet?

问题描述

由于我设置了ResultSet.TYPE_SCROLL_INSENSITVE(与Javadocs中的示例相同)，我得到了一个简单的代码来从MSSQL Server 2008中检索记录集，该记录集必须是可滚动的:

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);

不幸的是，当我想获得像rs.last(); int rowCount = rs.getRow();这样的行数时，我仍然得到了堆栈跟踪:

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)

为什么会这样，如何解决(顺便说一句，当我检查ResultSet的类型时，得到1003 ..)?

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

推荐答案

TYPE_SCROLL_INSENSITIVE的组合很可能与CONCUR_UPDATABLE不兼容.根据JDBC规范，如果驱动程序不能为请求的可滚动性和/或并发模式提供服务，则可以自由地将ResultSet降级.另请参见: http://jtds.sourceforge.net/resultSets.html :

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 |静态游标|重型|仅适用于只读并发(可更新的版本已降级). SQL Server会生成一个临时表，因此其他人所做的更改是不可见的.可滚动.

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.

指定CONCUR_UPDATABLE时确认驱动程序将降级.

Which confirms that the driver will downgrade when specifying CONCUR_UPDATABLE.

您可能要考虑使用TYPE_SCROLL_SENSITIVE，或者根本不将滚动性与可升级性结合使用.

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

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