Our application uses the Excel importer module. I try to import an xlsx file. When calling the StartImportByTemplate Java action for the first time the Java action throws the exception you see below. The second time I call the Java action, the import finishes succesfully without any exceptions. Importing xls files works fine. Can someone explain why the exception occurs only the first time I call the action and how to fix this? com.mendix.core.CoreRuntimeException: com.mendix.core.CoreException: com.mendix.core.CoreException: Document could not be imported, because: DTD factory class com.sun.org.apache.xerces.internal.impl.dv.dtd.DTDDVFactoryImpl does not extend from DTDDVFactory. at ImportExport.MC_GenericImport_ImportRequirement (JavaAction : 'Call 'StartImportByTemplate'') at ImportExport.MC_GenericImport_UploadNew (SubMicroflow : 'Call 'MC_GenericImport_ImportRequirement'') at ImportExport.MB_GenericImport_UploadNew_CatchException (SubMicroflow : 'Call 'MC_GenericImport_UploadNew'') Advanced stacktrace: at com.mendix.modules.microflowengine.MicroflowUtil.processException(SourceFile:158) Caused by: com.mendix.core.CoreRuntimeException: com.mendix.core.CoreException: com.mendix.core.CoreException: Document could not be imported, because: DTD factory class com.sun.org.apache.xerces.internal.impl.dv.dtd.DTDDVFactoryImpl does not extend from DTDDVFactory. at com.mendix.core.component.InternalCore.execute(SourceFile:274) Caused by: com.mendix.core.CoreException: com.mendix.core.CoreException: Document could not be imported, because: DTD factory class com.sun.org.apache.xerces.internal.impl.dv.dtd.DTDDVFactoryImpl does not extend from DTDDVFactory. at com.mendix.core.actionmanagement.ActionManager.executeSync(SourceFile:216) Caused by: com.mendix.core.CoreException: Document could not be imported, because: DTD factory class com.sun.org.apache.xerces.internal.impl.dv.dtd.DTDDVFactoryImpl does not extend from DTDDVFactory. at excelimporter.reader.ExcelImporter.startImport(ExcelImporter.java:133) Caused by: Document could not be imported, because: DTD factory class com.sun.org.apache.xerces.internal.impl.dv.dtd.DTDDVFactoryImpl does not extend from DTDDVFactory. at excelimporter.reader.readers.ExcelReader.importData(ExcelReader.java:420) Caused by: DTD factory class com.sun.org.apache.xerces.internal.impl.dv.dtd.DTDDVFactoryImpl does not extend from DTDDVFactory. at com.sun.org.apache.xerces.internal.impl.dv.DTDDVFactory.getInstance(DTDDVFactory.java:67) at com.sun.org.apache.xerces.internal.impl.dv.DTDDVFactory.getInstance(DTDDVFactory.java:49) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.<init>(XML11Configuration.java:578) at com.sun.org.apache.xerces.internal.parsers.XIncludeAwareParserConfiguration.<init>(XIncludeAwareParserConfiguration.java:130) at com.sun.org.apache.xerces.internal.parsers.XIncludeAwareParserConfiguration.<init>(XIncludeAwareParserConfiguration.java:91) at com.sun.org.apache.xerces.internal.parsers.SAXParser.<init>(SAXParser.java:111) at com.sun.org.apache.xerces.internal.parsers.SAXParser.<init>(SAXParser.java:96) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:526) at java.lang.Class.newInstance(Class.java:374) at org.xml.sax.helpers.NewInstance.newInstance(NewInstance.java:84) at org.xml.sax.helpers.XMLReaderFactory.loadClass(XMLReaderFactory.java:228) at org.xml.sax.helpers.XMLReaderFactory.createXMLReader(XMLReaderFactory.java:191) at excelimporter.reader.readers.ExcelXLSXDataReader.readData(ExcelXLSXDataReader.java:45) at excelimporter.reader.readers.ExcelReader.importData(ExcelReader.java:411) at excelimporter.reader.ExcelImporter.startImport(ExcelImporter.java:123) at excelimporter.actions.StartImportByTemplate.executeAction(StartImportByTemplate.java:54) at excelimporter.actions.StartImportByTemplate.executeAction(StartImportByTemplate.java:25) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:53) at com.mendix.core.actionmanagement.CoreAction.doCall(SourceFile:291) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:276) at com.mendix.core.actionmanagement.ActionManager.executeSync(SourceFile:205) at com.mendix.core.component.InternalCore.execute(SourceFile:262) at com.mendix.hx.execute(SourceFile:42) at com.mendix.ig.a(SourceFile:47) at com.mendix.if.a(SourceFile:193) at com.mendix.if.executeAction(SourceFile:148) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:53) at com.mendix.core.actionmanagement.CoreAction.doCall(SourceFile:291) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:276) at com.mendix.core.actionmanagement.ActionManager.executeSync(SourceFile:205) at com.mendix.core.component.InternalCore.executeSync(SourceFile:235) at com.mendix.modules.microflowengine.actions.SubMicroflowAction.execute(SourceFile:33) at com.mendix.ig.a(SourceFile:47) at com.mendix.if.a(SourceFile:193) at com.mendix.if.executeAction(SourceFile:148) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:53) at com.mendix.core.actionmanagement.CoreAction.doCall(SourceFile:291) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:276) at com.mendix.core.actionmanagement.ActionManager.executeSync(SourceFile:205) at com.mendix.core.component.InternalCore.executeSync(SourceFile:235) at com.mendix.modules.microflowengine.actions.SubMicroflowAction.execute(SourceFile:33) at com.mendix.ig.a(SourceFile:47) at com.mendix.if.a(SourceFile:193) at com.mendix.if.executeAction(SourceFile:148) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:53) at com.mendix.core.actionmanagement.AsyncAction.execute(SourceFile:26) at com.mendix.core.actionmanagement.CoreAction.doCall(SourceFile:291) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:276) at java.util.concurrent.FutureTask.run(FutureTask.java:262) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745)