“Bad major version” error when using Jasper-Reports on Websphere

[GREATEST]

When I try to fill a JasperReport in my Servlet running on Websphere 6.1 I get an \[code\]UnsupportedClassVersionError: Bad major version at offset=6\[/code\]. I guess that the compiled JasperReport has a different version (java 6?) than the jre on websphere can execute (which would be java 5), but I can not figure out why. Compiling the reports with maven or in the application (in the servlet) both leads to the error. According to the demo which was provided with JasperReports, which also shows how to use it with Java 1.5, I added following config to the jasperreports.properties:\[code\]org.eclipse.jdt.core.compiler.source=1.5org.eclipse.jdt.core.compiler.compliance=1.5org.eclipse.jdt.core.compiler.codegen.TargetPlatform=1.5\[/code\]But the error still exists. The language used in the report is Java, so which compiler is the correct one to use? \[code\]net.sf.jasperreports.engine.design.JRJdtCompiler\[/code\] or \[code\]net.sf.jasperreports.engine.design.JRJavacCompiler\[/code\]? Unfortunately, the documentation does not explain the difference between those two compilers...Edit: so fare I have been using the JRJavacCompiler. With the JRJdtCompiler I get a NullPointer Exception:\[code\] java.lang.NullPointerException at java.lang.Class.isAssignableFrom(Native Method) at net.sf.jasperreports.engine.fill.JRFillTextField.getFormat(JRFillTextField.java:706) at net.sf.jasperreports.engine.fill.JRFillTextField.evaluateText(JRFillTextField.java:394) at net.sf.jasperreports.engine.fill.JRFillTextField.evaluate(JRFillTextField.java:368) at net.sf.jasperreports.engine.fill.JRFillElementContainer.evaluate(JRFillElementContainer.java:258) at net.sf.jasperreports.engine.fill.JRFillBand.evaluate(JRFillBand.java:499) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillColumnBand(JRVerticalFiller.java:2036) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillDetail(JRVerticalFiller.java:760) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReportStart(JRVerticalFiller.java:270) at net.sf.jasperreports.engine.fill.JRVerticalFiller.fillReport(JRVerticalFiller.java:128) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:946) at net.sf.jasperreports.engine.fill.JRBaseFiller.fill(JRBaseFiller.java:864) at net.sf.jasperreports.engine.fill.JRFiller.fillReport(JRFiller.java:84) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:624) at net.sf.jasperreports.engine.JasperFillManager.fillReport(JasperFillManager.java:540) at com.swissre.sod.jone.web.server.FileStreamingServlet.doGet(FileStreamingServlet.java:48)\[/code\]