/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* 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
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.neethi;
import java.lang.reflect.ParameterizedType;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import javax.xml.namespace.QName;
import org.apache.neethi.builders.AssertionBuilder;
import org.apache.neethi.builders.converters.ConverterRegistry;
import org.apache.neethi.builders.xml.XMLPrimitiveAssertionBuilder;
import org.apache.neethi.util.Service;
/**
* AssertionFactory is used to create an Assertion from an Element. It uses an
* appropriate AssertionBuilder instance to create an Assertion based on the
* QName of the given element. Domain Policy authors could right custom
* AssertionBuilders to build Assertions for domain specific assertions.
*/
public class AssertionBuilderFactoryImpl implements AssertionBuilderFactory {
private Map<QName, AssertionBuilder<?>> registeredBuilders
= new ConcurrentHashMap<QName, AssertionBuilder<?>>();
protected AssertionBuilder defaultBuilder;
protected ConverterRegistry converters = new ConverterRegistry();
protected PolicyBuilder engine;
public AssertionBuilderFactoryImpl(PolicyBuilder eng) {
engine = eng;
for (AssertionBuilder builder : Service.providers(AssertionBuilder.class)) {
QName[] knownElements = builder.getKnownElements();
for (int i = 0; i < knownElements.length; i++) {
registeredBuilders.put(knownElements[i], builder);
}
}
defaultBuilder = new XMLPrimitiveAssertionBuilder();
}
public ConverterRegistry getConverterRegistry() {
return converters;
}
public PolicyBuilder getPolicyEngine() {
return engine;
}
/**
* Touch point for subclasses that would like to dynamically load
* builders when policies are first encountered
*/
protected void loadDynamic() {
}
/**
* Registers an AssertionBuilder with a specified QName.
*
* @param key the QName that the AssertionBuilder understand
* @param builder the AssertionBuilder that can build an Assertion from
* an element of specified type
*/
public void registerBuilder(QName key, AssertionBuilder<?> builder) {
loadDynamic();
registeredBuilders.put(key, builder);
}
public void registerBuilder(AssertionBuilder<?> builder) {
loadDynamic();
for (QName q : builder.getKnownElements()) {
registeredBuilders.put(q, builder);
}
}
/**
* Returns an assertion that is built using the specified element.
*
* @param element the element that the AssertionBuilder can use to build an
* Assertion.
* @return an Assertion that is built using the specified element.
*/
public Assertion build(Object element) {
loadDynamic();
AssertionBuilder builder;
QName qname = converters.findQName(element);
builder = registeredBuilders.get(qname);
if (builder == null) {
builder = handleNoRegisteredBuilder(qname);
}
return invokeBuilder(element, builder);
}
/**
* A subclass may want to log when an unknown assertion is encountered
* or possibly throw an exception or similar. Another option is to
* provide a unique AssertionBuilder specific for that QName.
* @param qname
* @return a AssertionBuilder to use for the element.
*/
protected AssertionBuilder handleNoRegisteredBuilder(QName qname) {
// if we can't locate an appropriate AssertionBuilder, we always use the
// XMLPrimitiveAssertionBuilder
return defaultBuilder;
}
@SuppressWarnings("unchecked")
private Assertion invokeBuilder(Object element, AssertionBuilder builder) {
Class<?> type = findAssertionBuilderTarget(builder.getClass());
return builder.build(converters.convert(element, type), this);
}
private Class<?> findAssertionBuilderTarget(Class<?> c) {
Class interfaces[] = c.getInterfaces();
for (int x = 0; x < interfaces.length; x++) {
if (interfaces[x] == AssertionBuilder.class) {
ParameterizedType pt = (ParameterizedType)c.getGenericInterfaces()[x];
return (Class)pt.getActualTypeArguments()[0];
}
}
if (c.getClass().getSuperclass() != null) {
return findAssertionBuilderTarget(c.getSuperclass());
}
return null;
}
/**
* Returns an AssertionBuilder that build an Assertion from an element of
* qname type.
*
* @param qname the type that the AssertionBuilder understands and builds an
* Assertion from
* @return an AssertionBuilder that understands qname type
*/
public AssertionBuilder<?> getBuilder(QName qname) {
loadDynamic();
return registeredBuilders.get(qname);
}
}