将Java w3c Document转换为XMLStreamReader

Question

我想在我们的代码库中重用一些现有的代码来接受XMLStreamReader我的应用程序将所需的数据作为w3c文档.

以下示例是最小测试用例:

public static void main(String[] args) throws Exception {
    DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = builderFactory.newDocumentBuilder();

    Document doc = builder.newDocument();

    Element rootElement = doc.createElement("Groups");
    doc.appendChild(rootElement);
    Element group = doc.createElement("Group");
    group.setTextContent("Wibble");
    rootElement.appendChild(group);

    DOMSource source = new DOMSource(doc);

    XMLStreamReader reader = XMLInputFactory.newInstance().createXMLStreamReader(source);

    reader.nextTag();
    System.out.println("NextTag:" + reader.getName());
}

预期的输出应该是这样的:NextTag:Groups但是抛出以下内容:

Exception in thread "main" javax.xml.stream.XMLStreamException: java.net.MalformedURLException
    at com.sun.xml.stream.XMLReaderImpl.setInputSource(XMLReaderImpl.java:196)
    at com.sun.xml.stream.XMLReaderImpl.<init>(XMLReaderImpl.java:179)
    at com.sun.xml.stream.ZephyrParserFactory.createXMLStreamReader(ZephyrParserFactory.java:139)
    at Main.main(Main.java:27)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Caused by: java.net.MalformedURLException
    at java.net.URL.<init>(URL.java:601)
    at java.net.URL.<init>(URL.java:464)
    at java.net.URL.<init>(URL.java:413)
    at com.sun.xml.stream.XMLEntityManager.startEntity(XMLEntityManager.java:762)
    at com.sun.xml.stream.XMLEntityManager.startDocumentEntity(XMLEntityManager.java:697)
    at com.sun.xml.stream.XMLDocumentScannerImpl.setInputSource(XMLDocumentScannerImpl.java:300)
    at com.sun.xml.stream.XMLReaderImpl.setInputSource(XMLReaderImpl.java:193)
    ... 8 

目前正在使用Java 6更新22.

更多信息:ZephyrParserFactory #jaxpSourcetoXMLInputSource的源代码似乎表明Source对象是通过应对它SystemId而不是DOMSource的实际内容来转换的.

更新:上面我的orignal测试用例实际上是使用我的项目类路径运行的,它实际上包含了JAXB 2.2.1库,后者又引入了sjsxp 1.0.1.在干净的类路径上运行会产生:

Exception in thread "main" java.lang.UnsupportedOperationException: Cannot create XMLStreamReader or XMLEventReader from a javax.xml.transform.dom.DOMSource
    at com.sun.xml.internal.stream.XMLInputFactoryImpl.jaxpSourcetoXMLInputSource(XMLInputFactoryImpl.java:302)
    at com.sun.xml.internal.stream.XMLInputFactoryImpl.createXMLStreamReader(XMLInputFactoryImpl.java:145)

这符合@Gary Rowe的回答.

Answer 1

这有点复杂，但是任何支持 XQJ API 的 XQuery 实现（例如 Saxon）都将允许您提供 DOM 作为查询“.”的输入，并以 XMLStreamReader 的形式获取结果。尽管涉及很多重型机械，但它应该非常高效。

使用 Saxon，您还可以使用类似的方法来短路 XQuery 方面

Document doc; // the DOM document
XMLStreamReader reader = new PullToStax(PullProvider.makePullProvider(new DocumentWrapper(doc));

但我认为 XQJ 方法更干净。