Decoration Calculation Error on Eclipse (STS)

When I try to open an xml file on STS I get an error.

The contents are as follows:

An internal error occurred during: "Decoration Calculation". org/springframework/tooling/boot/ls/xml/XMLRootElementContentDescriber2$QualifiedElement

When I looked at the log in the metadata, the following error message was output.

!ENTRY org.eclipse.jface 4 2 2020-12-24 20:20:29.699
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.jface".
!STACK 0
java.lang.NoClassDefFoundError: org/springframework/tooling/boot/ls/xml/XMLRootElementContentDescriber2$QualifiedElement
    at org.springframework.tooling.boot.ls.xml.XMLRootElementContentDescriber2.setInitializationData(XMLRootElementContentDescriber2.java:281)
    at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:254)
    at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:63)
    at org.eclipse.core.internal.content.ContentType.getDescriber(ContentType.java:293)
    at org.eclipse.core.internal.content.ContentTypeCatalog.collectMatchingByContents(ContentTypeCatalog.java:235)
    at org.eclipse.core.internal.content.ContentTypeCatalog.internalFindContentTypesFor(ContentTypeCatalog.java:455)
    at org.eclipse.core.internal.content.ContentTypeCatalog.internalFindContentTypesFor(ContentTypeCatalog.java:514)
    at org.eclipse.core.internal.content.ContentTypeCatalog.getDescriptionFor(ContentTypeCatalog.java:398)
    at org.eclipse.core.internal.content.ContentTypeCatalog.getDescriptionFor(ContentTypeCatalog.java:412)
    at org.eclipse.core.internal.content.ContentTypeMatcher.getDescriptionFor(ContentTypeMatcher.java:82)
    at org.eclipse.core.internal.resources.ContentDescriptionManager.readDescription(ContentDescriptionManager.java:455)
    at org.eclipse.core.internal.resources.ContentDescriptionManager.getDescriptionFor(ContentDescriptionManager.java:364)
    at org.eclipse.core.internal.resources.File.getContentDescription(File.java:266)
    at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.isClassFile(EditorUtility.java:656)
    at org.eclipse.jdt.internal.ui.javaeditor.EditorUtility.openInEditor(EditorUtility.java:169)
    at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:287)
    at org.eclipse.jdt.ui.actions.OpenAction.run(OpenAction.java:252)
    at org.eclipse.jdt.ui.actions.SelectionDispatchAction.dispatchRun(SelectionDispatchAction.java:274)
    at org.eclipse.jdt.ui.actions.SelectionDispatchAction.run(SelectionDispatchAction.java:252)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerActionGroup.handleOpen(PackageExplorerActionGroup.java:382)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerPart$4.open(PackageExplorerPart.java:554)
    at org.eclipse.ui.OpenAndLinkWithEditorHelper$InternalListener.open(OpenAndLinkWithEditorHelper.java:48)
    at org.eclipse.jface.viewers.StructuredViewer$2.run(StructuredViewer.java:796)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
    at org.eclipse.ui.internal.JFaceUtil.lambda$0(JFaceUtil.java:47)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:176)
    at org.eclipse.jface.viewers.StructuredViewer.fireOpen(StructuredViewer.java:793)
    at org.eclipse.jface.viewers.StructuredViewer.handleOpen(StructuredViewer.java:1108)
    at org.eclipse.jface.util.OpenStrategy.fireOpenEvent(OpenStrategy.java:275)
    at org.eclipse.jface.util.OpenStrategy.access$2(OpenStrategy.java:270)
    at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:310)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:89)
    at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4131)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1056)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3944)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3547)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1173)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1062)
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:155)
    at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:635)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:338)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:559)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:155)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:203)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:137)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:107)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:400)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:255)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:660)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:597)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1468)

What is the problem? The STS version is 4.3.2.

The solution for me was to remove the javascript label decoration by going to Windows - preferences - General - Apperance - Label Decorations and unchecking the Javascript override function indicator

Another possible solution might be running eclipse with the -clean option :

On Windows:

eclipse.exe -clean

This will clean you plug-ins cache which might resolve your issue