Java xtext如何获取根AST元素

我正在使用xtext来构建我的dsl，我添加了一个弹出操作，现在我需要的是当执行该操作以加载AST并转换它时，我尝试使用以下coe 加载根Ast元素的步骤

/*Environment configuration*/
StandaloneSetup standalone = new StandaloneSetup();
standalone.setPlatformUri(workingPath);
Injector injector = new MyDslStandaloneSetup().createInjectorAndDoEMFRegistration();
XtextResourceSet resourceSet = injector.getInstance(XtextResourceSet.class);
resourceSet.addLoadOption(XtextResource.OPTION_RESOLVE_ALL, Boolean.TRUE);

/*File parsing*/

Resource resource = resourceSet.createResource(URI.createURI(uriPrefix + fileName));
InputStream in = new FileInputStream(workingPath + fileName);
resource.load(in, resourceSet.getLoadOptions());

if(resource.getContents().size() == 0) {
    System.out.println("The file is empty: no folder has been generated");
    return null;
}
Prog model = (Prog) resource.getContents().get(0);
return model;

但不要工作，并提出这个例外：

!MESSAGE Invalid property category path: ValidationPropertiesPage (bundle: org.eclipse.wst.xml.ui, propertyPage: org.eclipse.wst.xml.ui.propertyPage.project.validation)
org.eclipse.emf.ecore.resource.Resource$IOWrappedException: Content is not allowed in prolog.
    at org.eclipse.emf.ecore.xmi.impl.XMLLoadImpl.load(XMLLoadImpl.java:195)
    at org.eclipse.emf.ecore.xmi.impl.XMLResourceImpl.doLoad(XMLResourceImpl.java:240)
    at org.eclipse.emf.ecore.resource.impl.ResourceImpl.load(ResourceImpl.java:1505)
    at org.xtext.example.mydsl.ui.popup.actions.RunClass.getProg(RunClass.java:203)
    at org.xtext.example.mydsl.ui.popup.actions.RunClass.run(RunClass.java:88)
    at org.eclipse.ui.internal.PluginAction.runWithEvent(PluginAction.java:251)
    at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
    at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501)
    at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1276)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3554)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3179)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1022)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:916)
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:86)
    at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:585)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:540)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1414)
Caused by: org.xml.sax.SAXParseExceptionpublicId: platform:/resource/prova/a.myDsl; systemId: platform:/resource/prova/a.myDsl; lineNumber: 4; columnNumber: 1; Content is not allowed in prolog.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:198)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:177)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:391)
    at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1404)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:1014)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:625)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:488)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:819)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:748)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:123)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1208)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:525)
    at javax.xml.parsers.SAXParser.parse(SAXParser.java:392)
    at org.eclipse.emf.ecore.xmi.impl.XMLLoadImpl.load(XMLLoadImpl.java:175)
    ... 34 more

---

如何加载ASt？？？

错误消息如下：

org.xml.sax.SAXParseException publicId: 
platform:/resource/prova/a.myDsl; systemId: platform:/resource/prova/a.myDsl; 
lineNumber: 4; columnNumber: 1; Content is not allowed in prolog

这意味着框架试图将您的DSL作为XML加载，但这是行不通的。这些错误的常见原因是没有注册文件扩展名

myDsl

使用此调用会发生这种情况：

org.eclipse.xtext.resource.IResourceServiceProvider.Registry.INSTANCE.getExtensionToFactoryMap().put("myDsl", ...);

确保为您的DSL调用此方法

另外，在编写Eclipse插件时，不能使用独立安装程序。这样做会破坏许多全局变量并导致虚假错误。对于Eclipse插件，DSL激活器将用于在UI包中搜索

*activator.java

在中有一个应该调用的方法

getInjector（）