org.apache.axiom.locator.ImplementationFactory Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing,
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* specific language governing permissions and limitations
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package org.apache.axiom.locator;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import javax.xml.namespace.QName;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.apache.axiom.locator.loader.OMMetaFactoryLoader;
import org.apache.axiom.om.OMAbstractFactory;
import org.apache.axiom.om.OMMetaFactory;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;
final class ImplementationFactory {
static final String DESCRIPTOR_RESOURCE = "META-INF/axiom.xml";
private static final String NS = "http://ws.apache.org/axiom/";
private static final QName QNAME_IMPLEMENTATIONS = new QName(NS, "implementations");
private static final QName QNAME_IMPLEMENTATION = new QName(NS, "implementation");
private static final QName QNAME_FEATURE = new QName(NS, "feature");
private static final QName QNAME_EXTENSION_INTERFACE = new QName(NS, "extensionInterface");
private static final Log log = LogFactory.getLog(ImplementationFactory.class);
private ImplementationFactory() {}
static Implementation createDefaultImplementation(Loader loader, String className) {
if (log.isDebugEnabled()) {
log.debug("Creating default implementation for class " + className);
}
OMMetaFactory metaFactory = (OMMetaFactory)load(loader, className);
return metaFactory == null ? null : new Implementation(null, metaFactory,
new Feature[] { new Feature(OMAbstractFactory.FEATURE_DEFAULT, Integer.MAX_VALUE, new Class[0]) });
}
private static Object load(Loader loader, String className) {
Class clazz;
try {
clazz = loader.load(className);
} catch (ClassNotFoundException ex) {
log.error("The class " + className + " could not be loaded", ex);
return null;
}
try {
return clazz.newInstance();
} catch (Exception ex) {
log.error("The class " + className + " could not be instantiated", ex);
return null;
}
}
static List parseDescriptor(Loader loader, URL url) {
if (log.isDebugEnabled()) {
log.debug("Loading " + url);
}
List implementations = new ArrayList();
try {
// Since this code is used to discover Axiom implementations, we have to use DOM here.
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
// Use URL#openStream() (instead of converting the URL to a String and passing it to the
// parser) to avoid situations where the parser can't reconstruct/interpret the URL.
InputStream in = url.openStream();
try {
Element root = dbf.newDocumentBuilder().parse(in).getDocumentElement();
QName rootQName = getQName(root);
if (rootQName.equals(QNAME_IMPLEMENTATIONS)) {
Node child = root.getFirstChild();
while (child != null) {
if (child instanceof Element) {
QName childQName = getQName(child);
if (childQName.equals(QNAME_IMPLEMENTATION)) {
Implementation implementation = parseImplementation(loader, (Element)child);
if (implementation != null) {
implementations.add(implementation);
}
} else {
log.warn("Skipping unexpected element " + childQName + "; only "
+ QNAME_IMPLEMENTATION + " is expected");
}
}
child = child.getNextSibling();
}
} else {
log.error(url + " is not a valid implementation descriptor: unexpected root element "
+ rootQName + "; expected " + QNAME_IMPLEMENTATIONS);
}
} finally {
in.close();
}
} catch (ParserConfigurationException ex) {
// If we get here, something went badly wrong
throw new Error(ex);
} catch (IOException ex) {
log.error("Unable to read " + url, ex);
} catch (SAXException ex) {
log.error("Parser error while reading " + url, ex);
}
if (log.isDebugEnabled()) {
log.debug("Discovered implementations: " + implementations);
}
return implementations;
}
private static Implementation parseImplementation(Loader loader, Element implementation) {
String name = implementation.getAttributeNS(null, "name");
if (name.length() == 0) {
log.error("Encountered " + QNAME_IMPLEMENTATION + " element without name attribute");
return null;
}
String loaderClassName = implementation.getAttributeNS(null, "loader");
if (loaderClassName.length() == 0) {
log.error("Encountered " + QNAME_IMPLEMENTATION + " element without loader attribute");
return null;
}
OMMetaFactory metaFactory = ((OMMetaFactoryLoader)load(loader, loaderClassName)).load(null);
if (metaFactory == null) {
return null;
}
List features = new ArrayList();
Node child = implementation.getFirstChild();
while (child != null) {
if (child instanceof Element) {
QName childQName = getQName(child);
if (childQName.equals(QNAME_FEATURE)) {
Feature feature = parseFeature(loader, (Element)child);
if (feature != null) {
features.add(feature);
}
} else {
log.warn("Skipping unexpected element " + childQName + "; only "
+ QNAME_FEATURE + " is expected");
}
}
child = child.getNextSibling();
}
return new Implementation(name, metaFactory, features.toArray(new Feature[features.size()]));
}
private static Feature parseFeature(Loader loader, Element feature) {
String name = feature.getAttributeNS(null, "name");
if (name.length() == 0) {
log.error("Encountered " + QNAME_FEATURE + " element without name attribute");
return null;
}
String priority = feature.getAttributeNS(null, "priority");
if (priority.length() == 0) {
log.error("Encountered " + QNAME_FEATURE + " element without priority attribute");
return null;
}
List> extensionInterfaces = new ArrayList>();
Node child = feature.getFirstChild();
while (child != null) {
if (child instanceof Element) {
QName childQName = getQName(child);
if (childQName.equals(QNAME_EXTENSION_INTERFACE)) {
String className = ((Element)child).getTextContent();
try {
extensionInterfaces.add(loader.load(className));
} catch (ClassNotFoundException ex) {
log.error("The class " + className + " could not be loaded", ex);
}
} else {
log.warn("Skipping unexpected element " + childQName + "; only "
+ QNAME_EXTENSION_INTERFACE + " is expected");
}
}
child = child.getNextSibling();
}
try {
return new Feature(name, Integer.parseInt(priority), extensionInterfaces.toArray(new Class[extensionInterfaces.size()]));
} catch (NumberFormatException ex) {
log.error("Invalid priority value '" + priority + "'; must be an integer");
return null;
}
}
private static QName getQName(Node node) {
String namespaceURI = node.getNamespaceURI();
return namespaceURI == null ? new QName(node.getLocalName()) : new QName(namespaceURI, node.getLocalName());
}
}
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