java中命名空间xpath的输出

我有下面的代码，在特定字段及其输出方面遇到了一些问题。名称空间已连接，但似乎未在必填字段上输出。这方面的任何信息都会很好

import org.w3c.dom.Document;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPathFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathExpressionException;
import java.io.ByteArrayInputStream;
import java.io.IOException;

public class test
{
 public static void main(String args[])

 {


     String xmlStr =    "<aws:UrlInfoResponse xmlns:aws=\"http://alexa.amazonaws.com/doc/2005-10-05/\">\n" +
                "    <aws:Response xmlns:aws=\"http://awis.amazonaws.com/doc/2005-07-11\">\n" +
                "        <aws:OperationRequest>\n" +
                "            <aws:RequestId>blah</aws:RequestId>\n" +
                "        </aws:OperationRequest>\n" +
                "        <aws:UrlInfoResult>\n" +
                "            <aws:Alexa>\n" +
                "                <aws:TrafficData>\n" +
                "                    <aws:DataUrl type=\"canonical\">harvard.edu/</aws:DataUrl>\n" +
                "                    <aws:Rank>1635</aws:Rank>\n" +
                "                </aws:TrafficData>\n" +
                "            </aws:Alexa>\n" +
                "        </aws:UrlInfoResult>\n" +
                "        <aws:ResponseStatus xmlns:aws=\"http://alexa.amazonaws.com/doc/2005-10-05/\">\n" +
                "            <aws:StatusCode>Success</aws:StatusCode>\n" +
                "        </aws:ResponseStatus>\n" +
                "    </aws:Response>\n" +
                "</aws:UrlInfoResponse>";

                    DocumentBuilderFactory xmlFact = DocumentBuilderFactory.newInstance();

                    xmlFact.setNamespaceAware(true);

        DocumentBuilder builder = null;
        try {
            builder = xmlFact.newDocumentBuilder();
        } catch (ParserConfigurationException e) {
            e.printStackTrace();       }

        Document doc = null;
        try {
            doc = builder.parse(

     new ByteArrayInputStream( xmlStr.getBytes()));
        } catch (SAXException e) {
            e.printStackTrace();     } catch (IOException e) {
            e.printStackTrace();       }






     System.out.println(doc.getDocumentElement().getNamespaceURI());
     System.out.println(xmlFact.isNamespaceAware());

  String xpathStr = "//aws:OperationRequest";

            XPathFactory xpathFact = XPathFactory.newInstance();

            XPath xpath = xpathFact.newXPath();

        String result = null;
        try {
            result = xpath.evaluate(xpathStr, doc);
        } catch (XPathExpressionException e) {
            e.printStackTrace();  //To change body of catch statement use File | Settings | File Templates.
        }

        System.out.println("XPath result is \"" +  result + "\"");


}
}

import org.w3c.dom.Document；
导入org.xml.sax.SAXException；
导入javax.xml.parsers.DocumentBuilderFactory；
导入javax.xml.parsers.DocumentBuilder；
导入javax.xml.parsers.parserConfiguration异常；
导入javax.xml.xpath.XPathFactory；
导入javax.xml.xpath.xpath；
导入javax.xml.xpath.XPathExpressionException；
导入java.io.ByteArrayInputStream；
导入java.io.IOException；
公开课考试
{
公共静态void main（字符串参数[]）
{
字符串xmlStr=“\n”+
“\n”+
“\n”+
“等等\n”+
“\n”+
“\n”+
“\n”+
“\n”+
“harvard.edu/\n”+
“1635\n”+
“\n”+
“\n”+
“\n”+
“\n”+
“成功\n”+
“\n”+
“\n”+
"";
DocumentBuilderFactory xmlFact=DocumentBuilderFactory.newInstance（）；
setNamespaceAware（true）；
DocumentBuilder=null；
试一试{
builder=xmlFact.newDocumentBuilder（）；
}捕获（ParserConfiguration异常e）{
e、 printStackTrace（）；}
单据单据=空；
试一试{
doc=builder.parse(
新的ByteArrayInputStream（xmlStr.getBytes（））；
}捕获（SAXE异常）{
e、 printStackTrace（）；}捕获（IOE异常）{
e、 printStackTrace（）；}
System.out.println（doc.getDocumentElement（）.getNamespaceURI（））；
System.out.println（xmlFact.isNamespaceAware（））；
字符串xpathStr=“//aws:OperationRequest”；
XPathFactory xpathFact=XPathFactory.newInstance（）；
XPath=xpathFact.newXPath（）；
字符串结果=null；
试一试{
result=xpath.evaluate（xpathStr，doc）；
}捕获（XPathExpressionException e）{
e、 printStackTrace（）；//要更改catch语句的主体，请使用文件|设置|文件模板。
}
System.out.println（“XPath结果为\”“+结果+”\”）；
}
}

Xpath中的命名空间匹配不仅仅是匹配前缀的字符串。您必须实际定义NamespaceContext对象并将其与xPath关联。实际上，如果文档和xPath中的前缀相同，这一点都不重要

private NamespaceContext ns = new NamespaceContext() {
public String getNamespaceURI(String prefix) {
if (prefix.equals("ns1") return "http://alexa.amazonaws.com/doc/2005-10-05/";
else return XMLConstants.NULL_NS_URI;
}
public String getPrefix(String namespace) {
throw new UnsupportedOperationException();
}
public Iterator getPrefixes(String namespace) {
throw new UnsupportedOperationException();
}};

XPathFactory xpfactory = XPathFactory.newInstance();
XPath xpath = xpfactory.newXPath();
xpath.setNamespaceContext(ns);

String xpathStr = "//ns1:OperationRequest";
//and so on