javax.xml，XPath不是从带有名称空间的XML中提取的 [英] javax.xml, XPath is not extracted from XML with namespaces
问题描述
有原始XML
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
<soap:Header>
<context xmlns="urn:zimbra">
<session id="555">555</session>
<change token="333"/>
</context>
</soap:Header>
<soap:Body>
<AuthResponse xmlns="urn:zimbraAccount">
<lifetime>172799999</lifetime>
<session id="555">555</session>
<skin>carbon</skin>
</AuthResponse>
</soap:Body>
</soap:Envelope>
以这种方式解析XML
The XML is parsed in this way
// javax.xml.parsers.*
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(pathToXml);
然后我试图通过XPath提取会话ID
Then I'm trying to extract session id by XPath
// javax.xml.xpath.*;
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
// next xpath does not work with Java and online xpath tester
//XPathExpression expr = xpath.compile("/soap:Envelope/soap:Header/context/session/text()");
// this xpath works with online xpath tester but does not with in Java
XPathExpression expr = xpath.compile("/soap:Envelope/soap:Header/*[name()='context']/*[name()='session']/text()");
String sessionId = (String)expr.evaluate(doc, XPathConstants.STRING);
此处测试
http://www.xpathtester.com/xpath/678ae9388e3ae2fc8406eb8cf14f3119
当XML简化为此
<Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
<Header>
<context>
<session id="555">555</session>
<change token="333"/>
</context>
</Header>
<Body>
<AuthResponse xmlns="urn:zimbraAccount">
<lifetime>172799999</lifetime>
<session id="555">555</session>
<skin>carbon</skin>
</AuthResponse>
</Body>
</Envelope>
此XPath完成其工作
This XPath does its job
XPathExpression expr = xpath.compile("/Envelope/Header/context/session/text()");
如何使用Java从原始XML中提取会话ID？
How to extract session id from "original" XML with Java?
更新：JDK 1.6
UPDATE: JDK 1.6
推荐答案
答案是你需要正确使用名称空间和名称空间前缀：
首先，在使用它之前调用它来识别你的 DocumentBuilderFactory 名称空间：
First, make your DocumentBuilderFactory namespace aware by calling this before you use it:
factory.setNamespaceAware(true);
然后执行此操作以检索所需的值：
Then do this to retrieve the value you want:
XPathFactory xPathfactory = XPathFactory.newInstance();
XPath xpath = xPathfactory.newXPath();
xpath.setNamespaceContext(new NamespaceContext() {
@Override
public String getNamespaceURI(String prefix) {
if (prefix.equals("soap")) {
return "http://www.w3.org/2003/05/soap-envelope";
}
if (prefix.equals("zmb")) {
return "urn:zimbra";
}
return XMLConstants.NULL_NS_URI;
}
@Override
public String getPrefix(String namespaceURI) {
throw new UnsupportedOperationException("Not supported yet.");
}
@Override
public Iterator getPrefixes(String namespaceURI) {
throw new UnsupportedOperationException("Not supported yet.");
}
});
XPathExpression expr =
xpath.compile("/soap:Envelope/soap:Header/zmb:context/zmb:session");
String sessionId = (String)expr.evaluate(doc, XPathConstants.STRING);
您可能需要在文件的开头添加一行来导入NamespaceContext类：
You may need to add a line to the beginning of your file to import the NamespaceContext class:
import javax.xml.namespace.NamespaceContext;
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