Birt数据源的有关问题

Birt数据源的问题.
普通的报表本人已经测试过能正确在WEB中显示.但考虑报表比较多,发布后会修改数据库连接参数,因此要求能统一修改连接参数,所以用了Library文件,并在其中定了数据源.但显示报表时总是提示:2008-4-15 23:37:31 org.eclipse.birt.data.engine.odaconsumer.ConnectionManager openConnection
严重: Cannot open connection.
org.eclipse.birt.report.data.oda.jdbc.JDBCException: Missing properties in Connection.open(Properties).
at org.eclipse.birt.report.data.oda.jdbc.Connection.open(Connection.java:112)
at org.eclipse.datatools.connectivity.oda.consumer.helper.OdaConnection.open(OdaConnection.java:235)
at org.eclipse.birt.data.engine.odaconsumer.ConnectionManager.openConnection(ConnectionManager.java:145)
at org.eclipse.birt.data.engine.executor.DataSource.newConnection(DataSource.java:134)

at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
2008-4-15 23:37:31 org.eclipse.birt.report.engine.data.dte.DataGenerationEngine doExecuteQuery
严重: Cannot open the connection for the driver: org.eclipse.birt.report.data.oda.jdbc
Missing properties in Connection.open(Properties).
2008-4-15 23:37:31 org.eclipse.birt.report.engine.data.dte.DataPresentationEngine doExecuteQuery
严重: Can't load the report query
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不管我是否使用JNDI数据源还是普通的JDBC数据源,都是一样的结果.
按网上有些文章中提到在Data source对象的beforeOpen事件中写代码,结果还是上面一样的错误.
不知有何解决思路.