Intellij Idea constantly gives a JDOMParseException Error

Question

Just a few days ago, I tried to run a class, and I got the following error:

Error:Internal error: (org.jdom.input.JDOMParseException) Error on line 1: Content is not allowed in prolog.
org.jdom.input.JDOMParseException: Error on line 1: Content is not allowed in prolog.
    at org.jdom.input.SAXBuilder.build(SAXBuilder.java:533)
    at org.jdom.input.SAXBuilder.build(SAXBuilder.java:946)
    at com.intellij.openapi.util.JDOMUtil.loadDocument(JDOMUtil.java:364)
    at com.intellij.openapi.util.JDOMUtil.loadDocument(JDOMUtil.java:342)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.tryLoadRootElement(JpsLoaderBase.java:99)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadRootElement(JpsLoaderBase.java:72)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadRootElement(JpsLoaderBase.java:43)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadComponents(JpsLoaderBase.java:55)
    at org.jetbrains.jps.model.serialization.JpsProjectLoader.loadFromDirectory(JpsProjectLoader.java:119)
    at org.jetbrains.jps.model.serialization.JpsProjectLoader.loadProject(JpsProjectLoader.java:98)
    at org.jetbrains.jps.model.serialization.impl.JpsSerializationManagerImpl.loadModel(JpsSerializationManagerImpl.java:41)
    at org.jetbrains.jps.cmdline.JpsModelLoaderImpl.loadModel(JpsModelLoaderImpl.java:45)
    at org.jetbrains.jps.cmdline.BuildRunner.load(BuildRunner.java:78)
    at org.jetbrains.jps.cmdline.BuildSession.runBuild(BuildSession.java:261)
    at org.jetbrains.jps.cmdline.BuildSession.run(BuildSession.java:124)
    at org.jetbrains.jps.cmdline.BuildMain$MyMessageHandler$1.run(BuildMain.java:238)
    at org.jetbrains.jps.service.impl.SharedThreadPoolImpl$1.run(SharedThreadPoolImpl.java:41)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:177)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:441)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:368)
    at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1436)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:999)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:117)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:649)
    at org.jdom.input.SAXBuilder.build(SAXBuilder.java:518)
    ... 21 more
Caused by: org.xml.sax.SAXParseException; lineNumber: 1; columnNumber: 1; Content is not allowed in prolog.
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:203)
    at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.fatalError(ErrorHandlerWrapper.java:177)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:441)
    at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:368)
    at com.sun.org.apache.xerces.internal.impl.XMLScanner.reportFatalError(XMLScanner.java:1436)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:999)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:606)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:117)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:510)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:848)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:777)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1213)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:649)
    at org.jdom.input.SAXBuilder.build(SAXBuilder.java:518)
    at org.jdom.input.SAXBuilder.build(SAXBuilder.java:946)
    at com.intellij.openapi.util.JDOMUtil.loadDocument(JDOMUtil.java:364)
    at com.intellij.openapi.util.JDOMUtil.loadDocument(JDOMUtil.java:342)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.tryLoadRootElement(JpsLoaderBase.java:99)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadRootElement(JpsLoaderBase.java:72)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadRootElement(JpsLoaderBase.java:43)
    at org.jetbrains.jps.model.serialization.JpsLoaderBase.loadComponents(JpsLoaderBase.java:55)
    at org.jetbrains.jps.model.serialization.JpsProjectLoader.loadFromDirectory(JpsProjectLoader.java:119)
    at org.jetbrains.jps.model.serialization.JpsProjectLoader.loadProject(JpsProjectLoader.java:98)
    at org.jetbrains.jps.model.serialization.impl.JpsSerializationManagerImpl.loadModel(JpsSerializationManagerImpl.java:41)
    at org.jetbrains.jps.cmdline.JpsModelLoaderImpl.loadModel(JpsModelLoaderImpl.java:45)
    at org.jetbrains.jps.cmdline.BuildRunner.load(BuildRunner.java:78)
    at org.jetbrains.jps.cmdline.BuildSession.runBuild(BuildSession.java:261)
    at org.jetbrains.jps.cmdline.BuildSession.run(BuildSession.java:124)
    at org.jetbrains.jps.cmdline.BuildMain$MyMessageHandler$1.run(BuildMain.java:238)
    at org.jetbrains.jps.service.impl.SharedThreadPoolImpl$1.run(SharedThreadPoolImpl.java:41)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

This did not happen to me earlier, and I did not change any XML file. I tried to run the other classes, only to get to the same result. I tried everything, including restarting IntelliJ and even uninstalling and installing it, but the error just would not stop.

I have already done a lot of research on this error, but none of them seemed to fit my case. Can anyone help me find out the course of this problem?

NOTE: There is a similar question here: Intellij IDEA crashed, and now throws an error

However, my Intellij IDEA did not crash, it was just not able to run properly.

Possible duplicate of http://stackoverflow.com/questions/25652140/intellij-content-is-not-allowed-in-prolog?rq=1 — Christian Hujer, Jan 01 '15 at 06:59

Christian Hujer · Accepted Answer · 2015-01-01T06:57:20.673

Looking at the described behavior, I think that something changed one of the files in .idea/runConfigurations. Too bad that the error message that you posted does not include the filename of the file that triggers this error. Check the files in .idea/runConfigurations with a text editor, I hope you find the culprit there.

The error message means that the file is not a well-formed XML file. More precisely it means that the file contains something which XML says is "content" at a position where "content" is not allowed: Somewhere at the start of the file before the document element. That start of the file is called prolog in XML.

The XML prolog may contain only the following things:

exactly one XML declaration, which if it appears must be the very first thing (only the byte order mark may precede the XML declaration),
comments, like 
processing instructions like <?xml-stylesheet ... ?>
whitespace (space, newline, tab etc.)
exactly zero or one DOCTYPE declarations.

Anything else in the prolog would break the XML file, it would no longer be XML, giving the errors you've seen.

If you cannot fix this manually, i.e. because file contents are gone or things like that, you can also do the following thing: Remove all files that were created by IntelliJ IDEA and create a new project by importing it from existing sources.

There is a `workspace.xml` file but it is empty. Do I have to do anything to it? — code_unknown, Jan 01 '15 at 06:12
As far as I know, the file `workspace.xml` certainly should not be empty. You could try creating a new project and compare the files with the current project. — Christian Hujer, Jan 01 '15 at 06:55
Actually I just copied it from another project and made a few tweaks. And the program worked. — code_unknown, Jan 01 '15 at 07:17

Intellij Idea constantly gives a JDOMParseException Error

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