[OmniFaces utilities 2.1] Convenience method to return a node list matching given XPath expression

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[OmniFaces utilities] The getNodeList() method return a node list matching given XPath expression.

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Method:

Usage:

Before reading this post, please read about Xml#createDocument().

This example was practically "ripped up" from OmniFaces 2.1, WebXml class, which is used to parses the /WEB-INF/web.xml and all /META-INF/web-fragment files found in the classpath and offers methods to obtain information from them which is not available by the standard Servlet API.

import org.omnifaces.util.Xml;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import javax.xml.xpath.XPath;

import javax.xml.xpath.XPathFactory;

...

private static final String WEB_XML = "/WEB-INF/web.xml";

// the following elements will be resolved

private static final String XPATH_WELCOME_FILE = "welcome-file-list/welcome-file";

private static final String XPATH_EXCEPTION_TYPE = "error-page/exception-type";

private static final String XPATH_SECURITY_CONSTRAINT = "security-constraint";

...

ServletContext servletContext = (ServletContext) Faces.getExternalContext().getContext();

List<URL> urls = new ArrayList<>();

urls.add(servletContext.getResource(WEB_XML));

      

try {

    Document document = Xml.createDocument(urls);

   

    // DOM root available in memory

    Element root = document.getDocumentElement();

    // XPath

    XPath xpath = XPathFactory.newInstance().newXPath();

   

    // resolve XPATH_WELCOME_FILE

    NodeList welcomeFileList = getNodeList(root, xpath, XPATH_WELCOME_FILE);

    // resolve XPATH_EXCEPTION_TYPE

    NodeList exceptionTypes = getNodeList(root, xpath, XPATH_EXCEPTION_TYPE);

  

    // resolve XPATH_SECURITY_CONSTRAINT

    NodeList constraints = getNodeList(root, xpath, XPATH_SECURITY_CONSTRAINT);

} catch (...) {

    // ...

}

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