xml-path/src/main/java/io/restassured/path/xml/config/XmlPathConfig.java
public XmlPathConfig declaredNamespace(String prefix, String namespaceURI) {
        Validate.notEmpty(prefix, "Prefix cannot be empty");
        Validate.notEmpty(namespaceURI, "Namespace URI cannot be empty");
        Map<String, String> updatedNamespaces = new HashMap<String, String>(declaredNamespaces);
        updatedNamespaces.put(prefix, namespaceURI);
        return new XmlPathConfig(jaxbObjectMapperFactory, defaultParserType, defaultDeserializer, charset, features, updatedNamespaces,
                properties, validating, true, allowDocTypeDeclaration);
    }
public XmlPathConfig declaredNamespace(String prefix, String namespaceURI) {
        Validate.notEmpty(prefix, "Prefix cannot be empty");
        Validate.notEmpty(namespaceURI, "Namespace URI cannot be empty");
        Map<String, String> updatedNamespaces = new HashMap<String, String>(declaredNamespaces);
        updatedNamespaces.put(prefix, namespaceURI);
        return new XmlPathConfig(jaxbObjectMapperFactory, defaultParserType, defaultDeserializer, charset, features, updatedNamespaces,
                properties, validating, true, allowDocTypeDeclaration);
    }
Declares a namespace.

@param prefix       The feature name, which is a fully-qualified URI.
@param namespaceURI The requested value of the feature (true or false).
@return A new XmlPathConfig instance
@see org.xml.sax.XMLReader#setFeature(java.lang.String, boolean)