# Error Java null key argument **URL:** \ **Category:** Ignition\ **Created:** [March 18, 2022, 11:18am UTC](https://forum.inductiveautomation.com/t/error-java-null-key-argument/57354 "2022-03-18T11:18:47Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![taguililla](https://avatars.discourse-cdn.com/v4/letter/t/f9ae1b/32.png) [@taguililla](https://forum.inductiveautomation.com/u/taguililla)\ **Post date:** [March 18, 2022, 11:18am UTC](https://forum.inductiveautomation.com/t/error-java-null-key-argument/57354/1 "2022-03-18T11:18:47Z")
Hello. We have the next error on Report viewer ![imagen](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/6/f657e9b5669a261566df7061be1e031aa1aa21f2.png) 12:14:53.320 [AWT-EventQueue-0] WARN reporting.Preview - Error generating preview java.util.concurrent.ExecutionException: java.lang.IllegalArgumentException: Null ‘key’ argument. at java.base/java.util.concurrent.FutureTask.report(Unknown Source) at java.base/java.util.concurrent.FutureTask.get(Unknown Source) at java.desktop/javax.swing.SwingWorker.get(Unknown Source) at com.inductiveautomation.reporting.designer.workspace.design.PreviewPanel$PreviewGenerator.done(PreviewPanel.java:109) at java.desktop/javax.swing.SwingWorker$5.run(Unknown Source) at java.desktop/javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(Unknown Source) at java.desktop/sun.swing.AccumulativeRunnable.run(Unknown Source) at java.desktop/javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(Unknown Source) at java.desktop/javax.swing.Timer.fireActionPerformed(Unknown Source) at java.desktop/javax.swing.Timer$DoPostEvent.run(Unknown Source) at java.desktop/java.awt.event.InvocationEvent.dispatch(Unknown Source) at java.desktop/java.awt.EventQueue.dispatchEventImpl(Unknown Source) at java.desktop/java.awt.EventQueue$4.run(Unknown Source) at java.desktop/java.awt.EventQueue$4.run(Unknown Source) at java.base/java.security.AccessController.doPrivileged(Native Method) at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) at java.desktop/java.awt.EventQueue.dispatchEvent(Unknown Source) at com.inductiveautomation.snap.swing.RibsEventQueue.dispatchEvent(RibsEventQueue.java:99) at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.desktop/java.awt.EventDispatchThread.pumpEvents(Unknown Source) at java.desktop/java.awt.EventDispatchThread.run(Unknown Source) Caused by: java.lang.IllegalArgumentException: Null ‘key’ argument. at org.jfree.data.DefaultKeyedValues.setValue(DefaultKeyedValues.java:229) at org.jfree.data.DefaultKeyedValues2D.setValue(DefaultKeyedValues2D.java:337) at org.jfree.data.DefaultKeyedValues2D.addValue(DefaultKeyedValues2D.java:303) at org.jfree.data.category.DefaultCategoryDataset.addValue(DefaultCategoryDataset.java:222) at org.jfree.data.category.DefaultCategoryDataset.addValue(DefaultCategoryDataset.java:237) at com.inductiveautomation.rm.shape.j2dshapes.CategoryChart.rpgShape(CategoryChart.java:159) at com.inductiveautomation.rm.shape.RMShape.rpgAll(RMShape.java:2842) at com.inductiveautomation.rm.shape.ReportOwner.rpg(ReportOwner.java:178) at com.inductiveautomation.rm.shape.RMParentShape.rpgChildren(RMParentShape.java:597) at com.inductiveautomation.rm.shape.RMPage.rpgChildren(RMPage.java:696) at com.inductiveautomation.rm.shape.RMParentShape.rpgAll(RMParentShape.java:584) at com.inductiveautomation.rm.shape.RMPage.rpgAll(RMPage.java:659) at com.inductiveautomation.rm.shape.ReportOwner.rpg(ReportOwner.java:178) at com.inductiveautomation.rm.shape.RMDocument.rpgChildren(RMDocument.java:1089) at com.inductiveautomation.rm.shape.RMParentShape.rpgAll(RMParentShape.java:584) at com.inductiveautomation.rm.shape.ReportOwner.rpg(ReportOwner.java:178) at com.inductiveautomation.rm.shape.ReportOwner.generateReport(ReportOwner.java:169) at com.inductiveautomation.rm.shape.RMDocument.generateReport(RMDocument.java:1065) at com.inductiveautomation.rm.shape.RMDocument.generateReport(RMDocument.java:1033) at com.inductiveautomation.reporting.designer.workspace.design.PreviewPanel$PreviewGenerator.doInBackground(PreviewPanel.java:102) at com.inductiveautomation.reporting.designer.workspace.design.PreviewPanel$PreviewGenerator.doInBackground(PreviewPanel.java:84) at java.desktop/javax.swing.SwingWorker$1.call(Unknown Source) at java.base/java.util.concurrent.FutureTask.run(Unknown Source) at java.desktop/javax.swing.SwingWorker.run(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.base/java.lang.Thread.run(Unknown Source) Could you help us? Thank you. Best regards. ---
**Author:** ![Transistor](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/transistor/32/3380_2.png) [@Transistor](https://forum.inductiveautomation.com/u/Transistor)\ **Post date:** [March 18, 2022, 1:18pm UTC](https://forum.inductiveautomation.com/t/error-java-null-key-argument/57354/2 "2022-03-18T13:18:09Z")
I don’t know anything much about reports but it looks like it’s expecting a dictionary with `"key": "value"` and that it’s not getting one. What parameters are you passing to the viewer? ---
**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\ **Post date:** [March 18, 2022, 2:37pm UTC](https://forum.inductiveautomation.com/t/error-java-null-key-argument/57354/3 "2022-03-18T14:37:54Z")
> [@taguililla](#): > > Caused by: java.lang.IllegalArgumentException: Null ‘key’ argument. > at org.jfree.data.DefaultKeyedValues.setValue(DefaultKeyedValues.java:229) > at org.jfree.data.DefaultKeyedValues2D.setValue(DefaultKeyedValues2D.java:337) > at org.jfree.data.DefaultKeyedValues2D.addValue(DefaultKeyedValues2D.java:303) > at org.jfree.data.category.DefaultCategoryDataset.addValue(DefaultCategoryDataset.java:222) > at org.jfree.data.category.DefaultCategoryDataset.addValue(DefaultCategoryDataset.java:237) > at com.inductiveautomation.rm.shape.j2dshapes.CategoryChart.rpgShape(CategoryChart.java:159) Specifically, you've got a null value where it's not expected on a category chart.