XPath 如何以不知道命名空间的方式识别谓词中的属性 [英] XPath how to identify an attribute in a predicate in a namespace-unaware way

问题描述

我有以下 XML 文件:

I have the following XML file:

<foo:a xmlns:foo=\"http://www.foo.com\">
    <foo:b foo:bar=\"zar\">
    </foo:b>
</foo:a>

要获取属性 bar 的 b 节点的值为zar"(都在正确的命名空间中)，我可以使用 XPath 表达式:

To get the b nodes with an attribute bar having the value "zar" (all in the correct namespace), I can use the XPath expression:

/foo:a/foo:b[@foo:bar=\"zar\"]

(foo"正确绑定到http://www.foo.com" - 见代码最后)

(with "foo" properly bound to "http://www.foo.com" - see code at the end)

但是，当我想以不知道命名空间的方式执行相同操作时，虽然我可以通过依赖 local-name() 函数从元素中删除命名空间，但我无法将它们从属性中移除.

However, when I want to do the same in a namespace-unaware way, though I can remove the namespace from the elements by relying on the local-name() function, I am not able to remove them from the attribute.

这是我能想到的最好的:

This is the best I can come up with:

/*[local-name()='a']/*[local-name()='b' and @foo:bar=\"zar\"]

(遗憾的是，其中 foo 用于限定 bar 属性).

(where foo is, regrettably, used to qualify the bar attribute).

如何在完全删除命名空间的情况下编写上述表达式?

How can I write the above expression with namespaces completely removed?

下面的代码已经在 CLASSPATH 上使用和不使用 Saxon-HE-9.4.jar 进行了测试，并产生了正确的结果，但我无法从第二个中获取 'foo' 命名空间前缀XPath 表达式！

Below code has been tested both with and without Saxon-HE-9.4.jar on the CLASSPATH and produces correct results, but I can't get the 'foo' namespace prefix out of the second XPath expression!

import java.io.*;
import java.util.*;
import javax.xml.xpath.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;
import javax.xml.namespace.NamespaceContext;

public class FooMain {

    public static void main(String args[]) throws Exception {

        String xmlSample = "<foo:a xmlns:foo=\"http://www.foo.com\"><foo:b foo:bar=\"zar\"></foo:b></foo:a>";
        XPath xpath = namespaceAwareXpath("foo", "http://www.foo.com");
        {
            System.out.printf("[NS-aware           ] Number of 'b' nodes with foo:bar attribute having the value \"zar\" is: %d\n", 
                              ((NodeList) xpath.compile("/foo:a/foo:b[@foo:bar=\"zar\"]").evaluate(stringToXML(xmlSample, true),
                               XPathConstants.NODESET)).getLength());
        }
        {
            System.out.printf("[NS-aware but using local-name() ] Number of 'b' nodes with foo:bar attribute having the value \"zar\" is: %d\n", 
                              ((NodeList) xpath.compile("/*[local-name()='a']/*[local-name()='b' and @foo:bar=\"zar\"]").evaluate(stringToXML(xmlSample, true),
                               XPathConstants.NODESET)).getLength());
        }
    }


    public static XPath namespaceAwareXpath(final String prefix, final String nsURI) {
        XPathFactory xPathfactory = XPathFactory.newInstance();
        XPath xpath = xPathfactory.newXPath();
        NamespaceContext ctx = new NamespaceContext() {
                @Override
                public String getNamespaceURI(String aPrefix) {
                    if (aPrefix.equals(prefix))
                        return nsURI;
                    else
                        return null;
                }
                @Override
                public Iterator getPrefixes(String val) {
                    throw new UnsupportedOperationException();
                }
                @Override
                public String getPrefix(String uri) {
                    throw new UnsupportedOperationException();
                }
            };
        xpath.setNamespaceContext(ctx);
        return xpath;
    }    

    private static Document stringToXML(String s, boolean nsAware) throws Exception {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        factory.setNamespaceAware(nsAware);
        DocumentBuilder builder = factory.newDocumentBuilder();
        return builder.parse(new ByteArrayInputStream(s.getBytes("UTF-8")));
    }


}

推荐答案

/*[local-name()='a']/*[local-name()='b' and @*[local-name() = 'bar']=\"zar\"]

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