Updating a working Java 11 build environment from Eclipse 2018-12 to 2019-03 introduced several thousand build errors in the format "The package org.w3c.dom is accessible from more than one module: <unnamed>, java.xml". Apparently these errors are all caused by a project importing a package via the traditional classpath that also exists in the JDK's modulepath. The error message is maddeningly vague; it gives no clue where it sees a conflict (i.e. some particular imported jar file). After resolving all obvious conflicts, I made a copy of my gwt-2.8.2 directory and hacked the gwt-dev.jar file to remove the packages that I see referenced in these error messages (netscape.javascript.*, javax.xml.*, org.xml.*, and org.w3c.*):
scrappy:gwt-2.8.2-mod jimdouglas$ zip -d gwt-dev.jar "org/w3c/*" "org/xml/*" "javax/xml/*" "netscape/javascript/*"
scrappy:gwt-2.9.0-mod jimdouglas$ zip -d gwt-dev.jar "org/w3c/*" "org/xml/*" "javax/xml/*" "netscape/javascript/*"
deleting: javax/xml/
deleting: javax/xml/datatype/
deleting: javax/xml/namespace/
deleting: javax/xml/parsers/
deleting: javax/xml/stream/
deleting: javax/xml/stream/events/
deleting: javax/xml/stream/util/
deleting: javax/xml/transform/
deleting: javax/xml/transform/dom/
deleting: javax/xml/transform/sax/
deleting: javax/xml/transform/stax/
deleting: javax/xml/transform/stream/
deleting: javax/xml/validation/
deleting: javax/xml/ws/
deleting: javax/xml/xpath/
deleting: netscape/javascript/
deleting: org/w3c/
deleting: org/w3c/css/
deleting: org/w3c/css/sac/
deleting: org/w3c/css/sac/helpers/
deleting: org/w3c/dom/
deleting: org/w3c/dom/bootstrap/
deleting: org/w3c/dom/css/
deleting: org/w3c/dom/events/
deleting: org/w3c/dom/html/
deleting: org/w3c/dom/ls/
deleting: org/w3c/dom/ranges/
deleting: org/w3c/dom/stylesheets/
deleting: org/w3c/dom/traversal/
deleting: org/w3c/dom/views/
deleting: org/w3c/dom/xpath/
deleting: org/xml/
deleting: org/xml/sax/
deleting: org/xml/sax/ext/
deleting: org/xml/sax/helpers/
deleting: javax/xml/XMLConstants.class
deleting: javax/xml/datatype/DatatypeConfigurationException.class
deleting: javax/xml/datatype/DatatypeConstants$1.class
deleting: javax/xml/datatype/DatatypeConstants$Field.class
deleting: javax/xml/datatype/DatatypeConstants.class
deleting: javax/xml/datatype/DatatypeFactory.class
deleting: javax/xml/datatype/Duration.class
deleting: javax/xml/datatype/FactoryFinder$ConfigurationError.class
deleting: javax/xml/datatype/FactoryFinder.class
deleting: javax/xml/datatype/SecuritySupport$1.class
deleting: javax/xml/datatype/SecuritySupport$2.class
deleting: javax/xml/datatype/SecuritySupport$3.class
deleting: javax/xml/datatype/SecuritySupport$4.class
deleting: javax/xml/datatype/SecuritySupport$5.class
deleting: javax/xml/datatype/SecuritySupport.class
deleting: javax/xml/datatype/XMLGregorianCalendar.class
deleting: javax/xml/namespace/NamespaceContext.class
deleting: javax/xml/namespace/QName$1.class
deleting: javax/xml/namespace/QName.class
deleting: javax/xml/parsers/DocumentBuilder.class
deleting: javax/xml/parsers/DocumentBuilderFactory.class
deleting: javax/xml/parsers/FactoryConfigurationError.class
deleting: javax/xml/parsers/FactoryFinder$ConfigurationError.class
deleting: javax/xml/parsers/FactoryFinder.class
deleting: javax/xml/parsers/FilePathToURI.class
deleting: javax/xml/parsers/ParserConfigurationException.class
deleting: javax/xml/parsers/SAXParser.class
deleting: javax/xml/parsers/SAXParserFactory.class
deleting: javax/xml/parsers/SecuritySupport$1.class
deleting: javax/xml/parsers/SecuritySupport$2.class
deleting: javax/xml/parsers/SecuritySupport$3.class
deleting: javax/xml/parsers/SecuritySupport$4.class
deleting: javax/xml/parsers/SecuritySupport$5.class
deleting: javax/xml/parsers/SecuritySupport.class
deleting: javax/xml/stream/EventFilter.class
deleting: javax/xml/stream/FactoryConfigurationError.class
deleting: javax/xml/stream/FactoryFinder$ConfigurationError.class
deleting: javax/xml/stream/FactoryFinder.class
deleting: javax/xml/stream/Location.class
deleting: javax/xml/stream/SecuritySupport$1.class
deleting: javax/xml/stream/SecuritySupport$2.class
deleting: javax/xml/stream/SecuritySupport$3.class
deleting: javax/xml/stream/SecuritySupport$4.class
deleting: javax/xml/stream/SecuritySupport$5.class
deleting: javax/xml/stream/SecuritySupport.class
deleting: javax/xml/stream/StreamFilter.class
deleting: javax/xml/stream/XMLEventFactory.class
deleting: javax/xml/stream/XMLEventReader.class
deleting: javax/xml/stream/XMLEventWriter.class
deleting: javax/xml/stream/XMLInputFactory.class
deleting: javax/xml/stream/XMLOutputFactory.class
deleting: javax/xml/stream/XMLReporter.class
deleting: javax/xml/stream/XMLResolver.class
deleting: javax/xml/stream/XMLStreamConstants.class
deleting: javax/xml/stream/XMLStreamException.class
deleting: javax/xml/stream/XMLStreamReader.class
deleting: javax/xml/stream/XMLStreamWriter.class
deleting: javax/xml/stream/events/Attribute.class
deleting: javax/xml/stream/events/Characters.class
deleting: javax/xml/stream/events/Comment.class
deleting: javax/xml/stream/events/DTD.class
deleting: javax/xml/stream/events/EndDocument.class
deleting: javax/xml/stream/events/EndElement.class
deleting: javax/xml/stream/events/EntityDeclaration.class
deleting: javax/xml/stream/events/EntityReference.class
deleting: javax/xml/stream/events/Namespace.class
deleting: javax/xml/stream/events/NotationDeclaration.class
deleting: javax/xml/stream/events/ProcessingInstruction.class
deleting: javax/xml/stream/events/StartDocument.class
deleting: javax/xml/stream/events/StartElement.class
deleting: javax/xml/stream/events/XMLEvent.class
deleting: javax/xml/stream/util/EventReaderDelegate.class
deleting: javax/xml/stream/util/StreamReaderDelegate.class
deleting: javax/xml/stream/util/XMLEventAllocator.class
deleting: javax/xml/stream/util/XMLEventConsumer.class
deleting: javax/xml/transform/ErrorListener.class
deleting: javax/xml/transform/FactoryFinder$ConfigurationError.class
deleting: javax/xml/transform/FactoryFinder.class
deleting: javax/xml/transform/OutputKeys.class
deleting: javax/xml/transform/Result.class
deleting: javax/xml/transform/SecuritySupport$1.class
deleting: javax/xml/transform/SecuritySupport$2.class
deleting: javax/xml/transform/SecuritySupport$3.class
deleting: javax/xml/transform/SecuritySupport$4.class
deleting: javax/xml/transform/SecuritySupport$5.class
deleting: javax/xml/transform/SecuritySupport.class
deleting: javax/xml/transform/Source.class
deleting: javax/xml/transform/SourceLocator.class
deleting: javax/xml/transform/Templates.class
deleting: javax/xml/transform/Transformer.class
deleting: javax/xml/transform/TransformerConfigurationException.class
deleting: javax/xml/transform/TransformerException.class
deleting: javax/xml/transform/TransformerFactory.class
deleting: javax/xml/transform/TransformerFactoryConfigurationError.class
deleting: javax/xml/transform/URIResolver.class
deleting: javax/xml/transform/dom/DOMLocator.class
deleting: javax/xml/transform/dom/DOMResult.class
deleting: javax/xml/transform/dom/DOMSource.class
deleting: javax/xml/transform/sax/SAXResult.class
deleting: javax/xml/transform/sax/SAXSource.class
deleting: javax/xml/transform/sax/SAXTransformerFactory.class
deleting: javax/xml/transform/sax/TemplatesHandler.class
deleting: javax/xml/transform/sax/TransformerHandler.class
deleting: javax/xml/transform/stax/StAXResult.class
deleting: javax/xml/transform/stax/StAXSource.class
deleting: javax/xml/transform/stream/FilePathToURI.class
deleting: javax/xml/transform/stream/StreamResult.class
deleting: javax/xml/transform/stream/StreamSource.class
deleting: javax/xml/validation/Schema.class
deleting: javax/xml/validation/SchemaFactory.class
deleting: javax/xml/validation/SchemaFactoryFinder$1.class
deleting: javax/xml/validation/SchemaFactoryFinder$2.class
deleting: javax/xml/validation/SchemaFactoryFinder$SingleIterator.class
deleting: javax/xml/validation/SchemaFactoryFinder.class
deleting: javax/xml/validation/SchemaFactoryLoader.class
deleting: javax/xml/validation/SecuritySupport$1.class
deleting: javax/xml/validation/SecuritySupport$2.class
deleting: javax/xml/validation/SecuritySupport$3.class
deleting: javax/xml/validation/SecuritySupport$4.class
deleting: javax/xml/validation/SecuritySupport$5.class
deleting: javax/xml/validation/SecuritySupport$6.class
deleting: javax/xml/validation/SecuritySupport$7.class
deleting: javax/xml/validation/SecuritySupport$8.class
deleting: javax/xml/validation/SecuritySupport.class
deleting: javax/xml/validation/TypeInfoProvider.class
deleting: javax/xml/validation/Validator.class
deleting: javax/xml/validation/ValidatorHandler.class
deleting: javax/xml/ws/WebServiceRef.class
deleting: javax/xml/ws/WebServiceRefs.class
deleting: javax/xml/xpath/SecuritySupport$1.class
deleting: javax/xml/xpath/SecuritySupport$2.class
deleting: javax/xml/xpath/SecuritySupport$3.class
deleting: javax/xml/xpath/SecuritySupport$4.class
deleting: javax/xml/xpath/SecuritySupport$5.class
deleting: javax/xml/xpath/SecuritySupport$6.class
deleting: javax/xml/xpath/SecuritySupport$7.class
deleting: javax/xml/xpath/SecuritySupport$8.class
deleting: javax/xml/xpath/SecuritySupport.class
deleting: javax/xml/xpath/XPath.class
deleting: javax/xml/xpath/XPathConstants.class
deleting: javax/xml/xpath/XPathException.class
deleting: javax/xml/xpath/XPathExpression.class
deleting: javax/xml/xpath/XPathExpressionException.class
deleting: javax/xml/xpath/XPathFactory.class
deleting: javax/xml/xpath/XPathFactoryConfigurationException.class
deleting: javax/xml/xpath/XPathFactoryFinder$1.class
deleting: javax/xml/xpath/XPathFactoryFinder$2.class
deleting: javax/xml/xpath/XPathFactoryFinder$SingleIterator.class
deleting: javax/xml/xpath/XPathFactoryFinder.class
deleting: javax/xml/xpath/XPathFunction.class
deleting: javax/xml/xpath/XPathFunctionException.class
deleting: javax/xml/xpath/XPathFunctionResolver.class
deleting: javax/xml/xpath/XPathVariableResolver.class
deleting: netscape/javascript/JSException.class
deleting: netscape/javascript/JSObject.class
deleting: org/w3c/css/sac/AttributeCondition.class
deleting: org/w3c/css/sac/COPYING.html
deleting: org/w3c/css/sac/CSSException.class
deleting: org/w3c/css/sac/CSSParseException.class
deleting: org/w3c/css/sac/CharacterDataSelector.class
deleting: org/w3c/css/sac/CombinatorCondition.class
deleting: org/w3c/css/sac/Condition.class
deleting: org/w3c/css/sac/ConditionFactory.class
deleting: org/w3c/css/sac/ConditionalSelector.class
deleting: org/w3c/css/sac/ContentCondition.class
deleting: org/w3c/css/sac/DescendantSelector.class
deleting: org/w3c/css/sac/DocumentHandler.class
deleting: org/w3c/css/sac/ElementSelector.class
deleting: org/w3c/css/sac/ErrorHandler.class
deleting: org/w3c/css/sac/InputSource.class
deleting: org/w3c/css/sac/LangCondition.class
deleting: org/w3c/css/sac/LexicalUnit.class
deleting: org/w3c/css/sac/Locator.class
deleting: org/w3c/css/sac/NegativeCondition.class
deleting: org/w3c/css/sac/NegativeSelector.class
deleting: org/w3c/css/sac/Parser.class
deleting: org/w3c/css/sac/PositionalCondition.class
deleting: org/w3c/css/sac/ProcessingInstructionSelector.class
deleting: org/w3c/css/sac/SACMediaList.class
deleting: org/w3c/css/sac/Selector.class
deleting: org/w3c/css/sac/SelectorFactory.class
deleting: org/w3c/css/sac/SelectorList.class
deleting: org/w3c/css/sac/SiblingSelector.class
deleting: org/w3c/css/sac/SimpleSelector.class
deleting: org/w3c/css/sac/helpers/ParserFactory.class
deleting: org/w3c/dom/Attr.class
deleting: org/w3c/dom/CDATASection.class
deleting: org/w3c/dom/CharacterData.class
deleting: org/w3c/dom/Comment.class
deleting: org/w3c/dom/DOMConfiguration.class
deleting: org/w3c/dom/DOMError.class
deleting: org/w3c/dom/DOMErrorHandler.class
deleting: org/w3c/dom/DOMException.class
deleting: org/w3c/dom/DOMImplementation.class
deleting: org/w3c/dom/DOMImplementationList.class
deleting: org/w3c/dom/DOMImplementationSource.class
deleting: org/w3c/dom/DOMLocator.class
deleting: org/w3c/dom/DOMStringList.class
deleting: org/w3c/dom/Document.class
deleting: org/w3c/dom/DocumentFragment.class
deleting: org/w3c/dom/DocumentType.class
deleting: org/w3c/dom/Element.class
deleting: org/w3c/dom/ElementTraversal.class
deleting: org/w3c/dom/Entity.class
deleting: org/w3c/dom/EntityReference.class
deleting: org/w3c/dom/NameList.class
deleting: org/w3c/dom/NamedNodeMap.class
deleting: org/w3c/dom/Node.class
deleting: org/w3c/dom/NodeList.class
deleting: org/w3c/dom/Notation.class
deleting: org/w3c/dom/ProcessingInstruction.class
deleting: org/w3c/dom/Text.class
deleting: org/w3c/dom/TypeInfo.class
deleting: org/w3c/dom/UserDataHandler.class
deleting: org/w3c/dom/bootstrap/DOMImplementationRegistry$1.class
deleting: org/w3c/dom/bootstrap/DOMImplementationRegistry$2.class
deleting: org/w3c/dom/bootstrap/DOMImplementationRegistry$3.class
deleting: org/w3c/dom/bootstrap/DOMImplementationRegistry$4.class
deleting: org/w3c/dom/bootstrap/DOMImplementationRegistry.class
deleting: org/w3c/dom/css/CSS2Properties.class
deleting: org/w3c/dom/css/CSSCharsetRule.class
deleting: org/w3c/dom/css/CSSFontFaceRule.class
deleting: org/w3c/dom/css/CSSImportRule.class
deleting: org/w3c/dom/css/CSSMediaRule.class
deleting: org/w3c/dom/css/CSSPageRule.class
deleting: org/w3c/dom/css/CSSPrimitiveValue.class
deleting: org/w3c/dom/css/CSSRule.class
deleting: org/w3c/dom/css/CSSRuleList.class
deleting: org/w3c/dom/css/CSSStyleDeclaration.class
deleting: org/w3c/dom/css/CSSStyleRule.class
deleting: org/w3c/dom/css/CSSStyleSheet.class
deleting: org/w3c/dom/css/CSSUnknownRule.class
deleting: org/w3c/dom/css/CSSValue.class
deleting: org/w3c/dom/css/CSSValueList.class
deleting: org/w3c/dom/css/Counter.class
deleting: org/w3c/dom/css/DOMImplementationCSS.class
deleting: org/w3c/dom/css/DocumentCSS.class
deleting: org/w3c/dom/css/ElementCSSInlineStyle.class
deleting: org/w3c/dom/css/RGBColor.class
deleting: org/w3c/dom/css/Rect.class
deleting: org/w3c/dom/css/ViewCSS.class
deleting: org/w3c/dom/events/DocumentEvent.class
deleting: org/w3c/dom/events/Event.class
deleting: org/w3c/dom/events/EventException.class
deleting: org/w3c/dom/events/EventListener.class
deleting: org/w3c/dom/events/EventTarget.class
deleting: org/w3c/dom/events/MouseEvent.class
deleting: org/w3c/dom/events/MutationEvent.class
deleting: org/w3c/dom/events/UIEvent.class
deleting: org/w3c/dom/html/HTMLAnchorElement.class
deleting: org/w3c/dom/html/HTMLAppletElement.class
deleting: org/w3c/dom/html/HTMLAreaElement.class
deleting: org/w3c/dom/html/HTMLBRElement.class
deleting: org/w3c/dom/html/HTMLBaseElement.class
deleting: org/w3c/dom/html/HTMLBaseFontElement.class
deleting: org/w3c/dom/html/HTMLBodyElement.class
deleting: org/w3c/dom/html/HTMLButtonElement.class
deleting: org/w3c/dom/html/HTMLCollection.class
deleting: org/w3c/dom/html/HTMLDListElement.class
deleting: org/w3c/dom/html/HTMLDOMImplementation.class
deleting: org/w3c/dom/html/HTMLDirectoryElement.class
deleting: org/w3c/dom/html/HTMLDivElement.class
deleting: org/w3c/dom/html/HTMLDocument.class
deleting: org/w3c/dom/html/HTMLElement.class
deleting: org/w3c/dom/html/HTMLFieldSetElement.class
deleting: org/w3c/dom/html/HTMLFontElement.class
deleting: org/w3c/dom/html/HTMLFormElement.class
deleting: org/w3c/dom/html/HTMLFrameElement.class
deleting: org/w3c/dom/html/HTMLFrameSetElement.class
deleting: org/w3c/dom/html/HTMLHRElement.class
deleting: org/w3c/dom/html/HTMLHeadElement.class
deleting: org/w3c/dom/html/HTMLHeadingElement.class
deleting: org/w3c/dom/html/HTMLHtmlElement.class
deleting: org/w3c/dom/html/HTMLIFrameElement.class
deleting: org/w3c/dom/html/HTMLImageElement.class
deleting: org/w3c/dom/html/HTMLInputElement.class
deleting: org/w3c/dom/html/HTMLIsIndexElement.class
deleting: org/w3c/dom/html/HTMLLIElement.class
deleting: org/w3c/dom/html/HTMLLabelElement.class
deleting: org/w3c/dom/html/HTMLLegendElement.class
deleting: org/w3c/dom/html/HTMLLinkElement.class
deleting: org/w3c/dom/html/HTMLMapElement.class
deleting: org/w3c/dom/html/HTMLMenuElement.class
deleting: org/w3c/dom/html/HTMLMetaElement.class
deleting: org/w3c/dom/html/HTMLModElement.class
deleting: org/w3c/dom/html/HTMLOListElement.class
deleting: org/w3c/dom/html/HTMLObjectElement.class
deleting: org/w3c/dom/html/HTMLOptGroupElement.class
deleting: org/w3c/dom/html/HTMLOptionElement.class
deleting: org/w3c/dom/html/HTMLParagraphElement.class
deleting: org/w3c/dom/html/HTMLParamElement.class
deleting: org/w3c/dom/html/HTMLPreElement.class
deleting: org/w3c/dom/html/HTMLQuoteElement.class
deleting: org/w3c/dom/html/HTMLScriptElement.class
deleting: org/w3c/dom/html/HTMLSelectElement.class
deleting: org/w3c/dom/html/HTMLStyleElement.class
deleting: org/w3c/dom/html/HTMLTableCaptionElement.class
deleting: org/w3c/dom/html/HTMLTableCellElement.class
deleting: org/w3c/dom/html/HTMLTableColElement.class
deleting: org/w3c/dom/html/HTMLTableElement.class
deleting: org/w3c/dom/html/HTMLTableRowElement.class
deleting: org/w3c/dom/html/HTMLTableSectionElement.class
deleting: org/w3c/dom/html/HTMLTextAreaElement.class
deleting: org/w3c/dom/html/HTMLTitleElement.class
deleting: org/w3c/dom/html/HTMLUListElement.class
deleting: org/w3c/dom/ls/DOMImplementationLS.class
deleting: org/w3c/dom/ls/LSException.class
deleting: org/w3c/dom/ls/LSInput.class
deleting: org/w3c/dom/ls/LSLoadEvent.class
deleting: org/w3c/dom/ls/LSOutput.class
deleting: org/w3c/dom/ls/LSParser.class
deleting: org/w3c/dom/ls/LSParserFilter.class
deleting: org/w3c/dom/ls/LSProgressEvent.class
deleting: org/w3c/dom/ls/LSResourceResolver.class
deleting: org/w3c/dom/ls/LSSerializer.class
deleting: org/w3c/dom/ls/LSSerializerFilter.class
deleting: org/w3c/dom/ranges/DocumentRange.class
deleting: org/w3c/dom/ranges/Range.class
deleting: org/w3c/dom/ranges/RangeException.class
deleting: org/w3c/dom/stylesheets/DocumentStyle.class
deleting: org/w3c/dom/stylesheets/LinkStyle.class
deleting: org/w3c/dom/stylesheets/MediaList.class
deleting: org/w3c/dom/stylesheets/StyleSheet.class
deleting: org/w3c/dom/stylesheets/StyleSheetList.class
deleting: org/w3c/dom/traversal/DocumentTraversal.class
deleting: org/w3c/dom/traversal/NodeFilter.class
deleting: org/w3c/dom/traversal/NodeIterator.class
deleting: org/w3c/dom/traversal/TreeWalker.class
deleting: org/w3c/dom/views/AbstractView.class
deleting: org/w3c/dom/views/DocumentView.class
deleting: org/w3c/dom/xpath/XPathEvaluator.class
deleting: org/w3c/dom/xpath/XPathException.class
deleting: org/w3c/dom/xpath/XPathExpression.class
deleting: org/w3c/dom/xpath/XPathNSResolver.class
deleting: org/w3c/dom/xpath/XPathNamespace.class
deleting: org/w3c/dom/xpath/XPathResult.class
deleting: org/xml/sax/AttributeList.class
deleting: org/xml/sax/Attributes.class
deleting: org/xml/sax/ContentHandler.class
deleting: org/xml/sax/DTDHandler.class
deleting: org/xml/sax/DocumentHandler.class
deleting: org/xml/sax/EntityResolver.class
deleting: org/xml/sax/ErrorHandler.class
deleting: org/xml/sax/HandlerBase.class
deleting: org/xml/sax/InputSource.class
deleting: org/xml/sax/Locator.class
deleting: org/xml/sax/Parser.class
deleting: org/xml/sax/SAXException.class
deleting: org/xml/sax/SAXNotRecognizedException.class
deleting: org/xml/sax/SAXNotSupportedException.class
deleting: org/xml/sax/SAXParseException.class
deleting: org/xml/sax/XMLFilter.class
deleting: org/xml/sax/XMLReader.class
deleting: org/xml/sax/ext/Attributes2.class
deleting: org/xml/sax/ext/Attributes2Impl.class
deleting: org/xml/sax/ext/DeclHandler.class
deleting: org/xml/sax/ext/DefaultHandler2.class
deleting: org/xml/sax/ext/EntityResolver2.class
deleting: org/xml/sax/ext/LexicalHandler.class
deleting: org/xml/sax/ext/Locator2.class
deleting: org/xml/sax/ext/Locator2Impl.class
deleting: org/xml/sax/helpers/AttributeListImpl.class
deleting: org/xml/sax/helpers/AttributesImpl.class
deleting: org/xml/sax/helpers/DefaultHandler.class
deleting: org/xml/sax/helpers/LocatorImpl.class
deleting: org/xml/sax/helpers/NamespaceSupport$Context.class
deleting: org/xml/sax/helpers/NamespaceSupport.class
deleting: org/xml/sax/helpers/NewInstance.class
deleting: org/xml/sax/helpers/ParserAdapter$AttributeListAdapter.class
deleting: org/xml/sax/helpers/ParserAdapter.class
deleting: org/xml/sax/helpers/ParserFactory.class
deleting: org/xml/sax/helpers/SecuritySupport$1.class
deleting: org/xml/sax/helpers/SecuritySupport$2.class
deleting: org/xml/sax/helpers/SecuritySupport$3.class
deleting: org/xml/sax/helpers/SecuritySupport$4.class
deleting: org/xml/sax/helpers/SecuritySupport.class
deleting: org/xml/sax/helpers/XMLFilterImpl.class
deleting: org/xml/sax/helpers/XMLReaderAdapter$AttributesAdapter.class
deleting: org/xml/sax/helpers/XMLReaderAdapter.class
deleting: org/xml/sax/helpers/XMLReaderFactory.class
scrappy:gwt-2.9.0-mod jimdouglas$
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Hi Vassilis,
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--Vassilis Virvilis
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I sincerely appreciate that you're trying to offer advice about this, Thomas, especially in the middle of the night where you are, but it's hard to imagine a non-Eclipse user fully understanding what I'm describing here. Is there nobody who still works on GWT who knows about Eclipse and the GWT Eclipse Plugin? This is a completely vanilla classpath-based, non-modulepath, Eclipse project that we've been updating with new versions of Eclipse, Java, and GWT for a decade. The modulepath conflict is introduced by the JDK itself, with the modularization of the entire JDK starting in Java 9. You can find many other people trying to make sense of this inexplicable error message over the past year or so:I first ran into this brick wall when I tried to update a Java 11 test environment from Eclipse 2018-12 to Eclipse 2019-03. I finally isolated the problem to the fact that GWT bundles several classes that are also distributed as part of the core JDK. The conflict is that GWT is classpath-oriented, and the JDK is now modulepath-oriented, and as of version 2019-03, Eclipse started to enforce the recent rule that a given class cannot appear in both the modulepath and the classpath.
For now, I've hacked around this by stripping the offending classes from GWT to eliminate the conflict. All of the classes that I was forced to elmininate exist in the JDK at least as early as Java 8 (I haven't checked Java 7), so it ought to be possible for the GWT team to simply drop them from gwt-dev.jar, since it can count on them existing in the JDK itself.
I do recognize that your strong preference is that every application should now be based on Maven, but ours isn't; it's a traditional application that just defines the classpath, and rearchitecting our development environment for a few dozen developers just isn't on the table anytime soon.