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java - 使用 XPath 处理 XML 文件生成的路径时出错

转载 作者：数据小太阳 更新时间：2023-10-29 02:16:28 25 4
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我有 XML 文件，我正在尝试使用 XPath 获取其路径的所有值，但它不会为 NameSpaces 生成值，例如:

//rss/channel/item/yweather:forecast/@low

或

//rss/channel/yweather:wind/text()

代码:使用的方法:

public class XmlSource{
    private XPathFactory factory = XPathFactory.newInstance();
    private XPath xpath = factory.newXPath();

    public Map<String, Object> update(String XML) throws ParserConfigurationException, SAXException, IOException, XPathExpressionException, TransformerException{

            XmlSource xml = new XmlSource();
            Map<String, Object> result = new HashMap<String, Object>();

            Document doc = convert(XML); // converting the String to a document (tested and working efficiently)
            xml.doc = doc; 
            xpath.setNamespaceContext(new NamespaceResolver(xml.doc));

            ArrayList<String> paths = xml.getAllPaths(); // to get the listed above paths (tested and working efficiently)  

                for(int i=0; i < paths.size() ; i++){
                result.put(paths.get(i), getValue(paths.get(i), xml.doc));
                }
            return result;

        }
    public String getValue(String path, Document doc) throws TransformerException, IOException, ParserConfigurationException, SAXException {


                this.doc = doc;


            try {

                XPathExpression expr = xpath.compile(path);
                Object result = expr.evaluate(this.doc, XPathConstants.STRING);

                return result.toString();
            } catch (XPathExpressionException ex) {
                return null;
            }
        }

}

NamespaceResolver 类:

import java.util.Iterator;
import javax.xml.XMLConstants;
import javax.xml.namespace.NamespaceContext;
import org.w3c.dom.Document;

public class NamespaceResolver implements NamespaceContext {
    private Document sourceDocument;

    public NamespaceResolver(Document document) {
        sourceDocument = document;
    }

    @Override
    public String getNamespaceURI(String prefix) {
        if (prefix.equals(XMLConstants.DEFAULT_NS_PREFIX)) {
            return sourceDocument.lookupNamespaceURI(null);
        } else {
            return sourceDocument.lookupNamespaceURI(prefix);
        }
    }

    @Override
    public String getPrefix(String namespaceURI) {
        return sourceDocument.lookupPrefix(namespaceURI);
    }

    @Override
    public Iterator<String> getPrefixes(String namespaceURI) {
        return null;
    }
}

抛出的异常:

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
        at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
        at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:30)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
        at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
        at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
    --------------- linked to ------------------
    javax.xml.xpath.XPathExpressionException
        org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
    //rss/channel/item/yweather:condition/@text
    //rss/channel/item/yweather:forecast/@code
    //rss/channel/item/yweather:forecast/@date
    //rss/channel/item/yweather:forecast/@day
    //rss/channel/item/yweather:forecast/@high
    //rss/channel/item/yweather:forecast/@low
    //rss/channel/item/yweather:forecast/@text
    //rss/channel/item/yweather:forecast/@code
    //rss/channel/item/yweather:forecast/@date
    //rss/channel/item/yweather:forecast/@day
    //rss/channel/item/yweather:forecast/@high
    //rss/channel/item/yweather:forecast/@low
    //rss/channel/item/yweather:forecast/@text
    --------------- linked to ------------------
    javax.xml.xpath.XPathExpressionException
    dAccessorImpl.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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
        at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
        at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
        at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
        at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:30)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
        at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
        at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
    Caused by: com.sun.org.apache.xpath.internal.domapi.XPathStylesheetDOM3Exception: Prefix must resolve to a namespace: yweather
        at com.sun.org.apache.xpath.internal.compiler.XPathParser.errorForDOM3(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.Lexer.mapNSTokens(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.Lexer.tokenize(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.Lexer.tokenize(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.XPathParser.initXPath(Unknown Source)
        at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source)
        at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source)
        ... 30 more
    com.sun.org.apache.xpath.internal.domapi.XPathStylesheetDOM3Exception: Prefix must resolve to a namespace: yweather
        at com.sun.org.apache.xpath.internal.compiler.XPathParser.errorForDOM3(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.Lexer.mapNSTokens(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.Lexer.tokenize(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.Lexer.tokenize(Unknown Source)
        at com.sun.org.apache.xpath.internal.compiler.XPathParser.initXPath(Unknown Source)
        at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source)
        at com.sun.org.apache.xpath.internal.XPath.<init>(Unknown Source)
        at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.compile(Unknown Source)
        at com.nc.inotify.dp.xml.impl.XmlSource.getValue(XmlSource.java:180)
        at com.nc.inotify.dp.xml.impl.XmlSource.update(XmlSource.java:284)
        at com.nc.inotify.dp.xml.impl.XmlSourceFactory.getSource(XmlSourceFactory.java:155)
        at com.nc.inotify.dp.xml.junit.TXmlSourceFactory.tesGetSource(TXmlSourceFactory.java:139)
        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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
        at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
        at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
        at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
        at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
        at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:30)
        at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
        at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
        at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
    --------------- linked to ------------------
    javax.xml.xpath.XPathExpressionException
        at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.compile(Unknown Source)
        at com.nc.inotify.dp.xml.impl.XmlSource.getValue(XmlSource.java:180)
        at com.nc.inotify.dp.xml.impl.XmlSource.update(XmlSource.java:284)
        at com.nc.inotify.dp.xml.impl.XmlSourceFactory.getSource(XmlSourceFactory.java:155)
        at com.nc.inotify.dp.xml.junit.TXmlSourceFactory.tesGetSource(TXmlSourceFactory.java:139)
        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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
        at 
    //rss/channel/item/yweather:forecast/text()
    //rss/channel/item/guid/text()
    DONE

最佳答案

我能够通过使用不支持命名空间的 DocumentBuilderFactory 重现您的错误。

假设您的 convert 方法看起来像这样:

DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(inputSource);

那么你可以试试这个:

DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
dbFactory.setNamespaceAware(true);
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(inputSource);

这可以解释为什么 NamespaceResolver 无法获取 namespaceURI。

关于java - 使用 XPath 处理 XML 文件生成的路径时出错，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/16899419/

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