java - Xpath - 评估函数返回 javax.xml.transform.TransformerException

Question

这是我第一次使用 XPath，我正在尝试查询一个非常基本的示例。

    String xml = "<resp><status>good</status><msg>hi</msg></resp>";

    XPathFactory xpathFactory = XPathFactory.newInstance();
    javax.xml.xpath.XPath xpath = xpathFactory.newXPath();

    InputSource source = new InputSource(new StringReader(xml));

    String status = "";
    try {
        status = (String) xpath.evaluate("//resp/status", source,XPathConstants.STRING);
    } catch (Exception e) {
        e.printStackTrace();
    }

    System.out.println("status=" + status);

我收到以下异常:

javax.xml.transform.TransformerException: Unable to evaluate expression using this context at com.sun.org.apache.xpath.internal.XPath.execute(Unknown Source) at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.eval(Unknown Source) at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.evaluate(Unknown Source) at Heandlers.HTTP.x(HTTP.java:74) at Views.Main.main(Main.java:15) Caused by: java.lang.RuntimeException: Unable to evaluate expression using this context at com.sun.org.apache.xpath.internal.axes.NodeSequence.setRoot(Unknown Source) at com.sun.org.apache.xpath.internal.axes.LocPathIterator.execute(Unknown Source) ... 5 more --------- java.lang.RuntimeException: Unable to evaluate expression using this context at com.sun.org.apache.xpath.internal.axes.NodeSequence.setRoot(Unknown Source) at com.sun.org.apache.xpath.internal.axes.LocPathIterator.execute(Unknown Source) at com.sun.org.apache.xpath.internal.XPath.execute(Unknown Source) at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.eval(Unknown Source) at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.evaluate(Unknown Source) at Heandlers.HTTP.x(HTTP.java:74) at Views.Main.main(Main.java:15) --------------- linked to ------------------ javax.xml.xpath.XPathExpressionException: javax.xml.transform.TransformerException: Unable to evaluate expression using this context at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.evaluate(Unknown Source) at Heandlers.HTTP.x(HTTP.java:74) at Views.Main.main(Main.java:15) Caused by: javax.xml.transform.TransformerException: Unable to evaluate expression using this context at com.sun.org.apache.xpath.internal.XPath.execute(Unknown Source) at com.sun.org.apache.xpath.internal.jaxp.XPathImpl.eval(Unknown Source) ... 3 more Caused by: java.lang.RuntimeException: Unable to evaluate expression using this context at com.sun.org.apache.xpath.internal.axes.NodeSequence.setRoot(Unknown Source) at com.sun.org.apache.xpath.internal.axes.LocPathIterator.execute(Unknown Source) ... 5 more status=

有什么建议吗？

Answer 1

听起来您正在使用无效的 InputSource，例如org.w3c.css.sac.InputSource。确保您已导入 org.xml.sax.InputSource。