使用 Commons JXPath 解析 XML 的问题 [英] Issue with XML parsing using Commons JXPath

问题描述

我正在尝试使用 Apache Commons JXPath 解析 XML.但是由于某种原因，它无法在解析 xml 后识别子节点.这是示例代码:

I'm trying to parse a XML using Apache Commons JXPath. But for some reason, its not able to identify the child nodes after the xml is being parsed. Here's the sample code :

private static void processUrl(String seed){
    String test = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><feed xmlns=\"http://www.w3.org/2005/Atom\" xmlns:media=\"http://search.yahoo.com/mrss/\" xmlns:openSearch=\"http://a9.com/-/spec/opensearchrss/1.0/\" xmlns:gd=\"http://schemas.google.com/g/2005\" xmlns:yt=\"http://gdata.youtube.com/schemas/2007\"><id>http://gdata.youtube.com/feeds/api/videos</id><logo>http://www.youtube.com/img/pic_youtubelogo_123x63.gif</logo><link rel=\"alternate\" type=\"text/html\" href=\"http://www.youtube.com\"/><author><name>YouTube</name><uri>http://www.youtube.com/</uri></author><generator version=\"2.1\" uri=\"http://gdata.youtube.com\">YouTube data API</generator><openSearch:totalResults>144</openSearch:totalResults><entry><id>http://gdata.youtube.com/feeds/api/videos/P1lDDu9L5YQ</id><published>2010-09-20T17:41:38.000Z</published><updated>2011-09-18T22:15:38.000Z</updated><category scheme=\"http://schemas.google.com/g/2005#kind\" term=\"http://gdata.youtube.com/schemas/2007#video\"/><link rel=\"alternate\" type=\"text/html\" href=\"http://www.youtube.com/watch?v=P1lDDu9L5YQ&amp;feature=youtube_gdata\"/></entry></feed>";
    Document doc = null;
    try{
        DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
        ByteArrayInputStream bais = new ByteArrayInputStream(test.toString().getBytes("UTF8"));
        doc = builder.parse(bais);
        bais.close();

        JXPathContext ctx = JXPathContext.newContext(doc);
        List entryNodes = ctx.selectNodes("/feed/entry");
        System.out.println("number of threadNodes " + entryNodes.size());
        int totalThreads = 0;
        for (Object each : entryNodes) {
            totalThreads++;
            Node eachEntryNode = (Node) each;
            JXPathContext msgCtx = JXPathContext.newContext(eachEntryNode);
            String title = (String) msgCtx.getValue("title");
        }
    }catch (Exception ex) {
        ex.printStackTrace();
    }
}

我之前使用过 JXPath，从来没有遇到过任何问题.我调试了文档对象，它似乎没有子节点 () for .我能看到的只是根元素.我也尝试过 DOMParser，但没有任何运气.

I've used JXPath earlier and never had any issues. I debugged the document object,it doesn't seemed to have the child node () for . All I'm able to see is the root element. I also tried DOMParser without any luck.

DOMParser parser = new DOMParser();
        Document doc = (Document) parser.parseXML(new ByteArrayInputStream(sb0.toString().getBytes("UTF-8")));

如果有人可以提供有关此用途的指示，我将不胜感激.

I'll appreciate if someone can provide pointers to this isuse.

推荐答案

这个问题与 JXPath 如何处理默认命名空间有关，它紧跟 XPath 1.0 规范.这也解释了为什么在删除默认命名空间 http://www.w3.org/2005/Atom 后它仍然有效.为了让它与默认命名空间一起工作，您可以执行以下操作:

This issue has to do with how JXPath handles default namespaces, which closely follows the XPath 1.0 specification. This also explains why it worked after you removed the default namespace http://www.w3.org/2005/Atom. In order to get it to work with the default namespace you can do the following:

JXPathContext ctx = JXPathContext.newContext(doc.getDocumentElement());
// Register the default namespace, giving it a prefix of your choice
ctx.registerNamespace("myfeed", "http://www.w3.org/2005/Atom");

// Now query for entry elements using the registered prefix
List entryNodes = ctx.selectNodes("myfeed:entry");

有关该问题的更多信息，请参阅以下链接.

For more information on the issue see the following links.

http://markmail.org/message/7iqw4bjrkwerbh46

制作 jxpath命名空间感知

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