Jasper Report iReport - unterschiedliche Datenquellen

#1
Hallo Zusammen,
ich hoffe Ihr könnt mir weiter helfen.
Ich habe ein Report mit einer XML-Datei als Datasource, nun möchte ich mit einem Subreport auf eine Oracle-Datenbank zugreifen um dort an weitere Informationen zu gelangen.

wenn ich ausschließlich mit XML oder Oracle arbeite funktioniert es.
Sprich die Connections sind richtig.

Für die Anbindung hab ich einen Parameter "REPORT_SQL_CONNECTION" erzeugt und den SQL-Connectionstring dort hinterlegt.
Java:
java.sql.DriverManager.getConnection("jdbc:oracle:thin:@Server:1521:Database", "user", "pw")
diesen Parameter "$P{REPORT_SQL_CONNECTION}" hab ich bei Subreport unter "Datenquellen Ausdruck verwenden" hinterlegt.

nun bekomme ich die folgende Fehlermeldung.
Java:
Fehler beim Füllen... Error evaluating expression :     
Source text : $P{REPORT_SQL_CONNECTION}
java.lang.ClassCastException: oracle.jdbc.driver.T4CConnection cannot be cast to net.sf.jasperreports.engine.JRDataSource     
at HRPRT_1491921776866_154485.evaluate3(HRPRT_1491921776866_154485:2137)     
at HRPRT_1491921776866_154485.evaluate2(HRPRT_1491921776866_154485:1988)     
at HRPRT_1491921776866_154485.evaluate1(HRPRT_1491921776866_154485:1458)     
at HRPRT_1491921776866_154485.evaluate(HRPRT_1491921776866_154485:919)     
at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:186)     
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:537)     
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:505)     
at net.sf.jasperreports.engine.fill.JRFillElement.evaluateExpression(JRFillElement.java:813)     
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:337)     
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:257)     
at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275)     
at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113)     
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:895)     
at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:123)     
at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:420)     
at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:256)     
at it.businesslogic.ireport.IReportCompiler.run(IReportCompiler.java:1053)     
at java.lang.Thread.run(Unknown Source) 

NESTED BY :  java.lang.ClassCastException: oracle.jdbc.driver.T4CConnection cannot be cast to net.sf.jasperreports.engine.JRDataSource     
at HRPRT_1491921776866_154485.evaluate3(HRPRT_1491921776866_154485:2137)     
at HRPRT_1491921776866_154485.evaluate2(HRPRT_1491921776866_154485:1988)     
at HRPRT_1491921776866_154485.evaluate1(HRPRT_1491921776866_154485:1458)     
at HRPRT_1491921776866_154485.evaluate(HRPRT_1491921776866_154485:919)     
at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:186)     
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:537)     
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:505)     
at net.sf.jasperreports.engine.fill.JRFillElement.evaluateExpression(JRFillElement.java:813)     
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:337)     
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:257)     
at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275)     
at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113)     
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:895)     
at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:123)     
at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:420)     
at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:256)     
at it.businesslogic.ireport.IReportCompiler.run(IReportCompiler.java:1053)     
at java.lang.Thread.run(Unknown Source) 

NESTED BY :  net.sf.jasperreports.engine.fill.JRExpressionEvalException: Error evaluating expression :      Source text : $P{REPORT_SQL_CONNECTION}     
at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:197)     
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:537)     
at net.sf.jasperreports.engine.fill.JRCalculator.evaluate(JRCalculator.java:505)     
at net.sf.jasperreports.engine.fill.JRFillElement.evaluateExpression(JRFillElement.java:813)     
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluateSubreport(JRFillSubreport.java:337)     
at net.sf.jasperreports.engine.fill.JRFillSubreport.evaluate(JRFillSubreport.java:257)     
at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:275)     
at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:426)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:1380)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:692)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:255)     
at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:113)     
at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:895)     
at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:123)      a
t net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:420)     
at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:256)     
at it.businesslogic.ireport.IReportCompiler.run(IReportCompiler.java:1053)     
at java.lang.Thread.run(Unknown Source)

Caused by: java.lang.ClassCastException: oracle.jdbc.driver.T4CConnection cannot be cast to net.sf.jasperreports.engine.JRDataSource     
at HRPRT_1491921776866_154485.evaluate3(HRPRT_1491921776866_154485:2137)     
at HRPRT_1491921776866_154485.evaluate2(HRPRT_1491921776866_154485:1988)     
at HRPRT_1491921776866_154485.evaluate1(HRPRT_1491921776866_154485:1458)     
at HRPRT_1491921776866_154485.evaluate(HRPRT_1491921776866_154485:919)     
at net.sf.jasperreports.engine.fill.JREvaluator.evaluate(JREvaluator.java:186)      ... 17 more
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