/*
* Copyright 2002-2012 the original author or authors.
*
* Licensed 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.springframework.beans.factory.xml;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
/**
* Base interface used by the {@link DefaultBeanDefinitionDocumentReader}
* for handling custom namespaces in a Spring XML configuration file.
*
* <p>Implementations are expected to return implementations of the
* {@link BeanDefinitionParser} interface for custom top-level tags and
* implementations of the {@link BeanDefinitionDecorator} interface for
* custom nested tags.
*
* <p>The parser will call {@link #parse} when it encounters a custom tag
* directly under the {@code <beans>} tags and {@link #decorate} when
* it encounters a custom tag directly under a {@code <bean>} tag.
*
* <p>Developers writing their own custom element extensions typically will
* not implement this interface directly, but rather make use of the provided
* {@link NamespaceHandlerSupport} class.
*
* @author Rob Harrop
* @author Erik Wiersma
* @since 2.0
* @see DefaultBeanDefinitionDocumentReader
* @see NamespaceHandlerResolver
*/
public interface NamespaceHandler {
/**
* Invoked by the {@link DefaultBeanDefinitionDocumentReader} after
* construction but before any custom elements are parsed.
* @see NamespaceHandlerSupport#registerBeanDefinitionParser(String, BeanDefinitionParser)
*/
void init();
/**
* Parse the specified {@link Element} and register any resulting
* {@link BeanDefinition BeanDefinitions} with the
* {@link org.springframework.beans.factory.support.BeanDefinitionRegistry}
* that is embedded in the supplied {@link ParserContext}.
* <p>Implementations should return the primary {@code BeanDefinition}
* that results from the parse phase if they wish to be used nested
* inside (for example) a {@code <property>} tag.
* <p>Implementations may return {@code null} if they will
* <strong>not</strong> be used in a nested scenario.
* @param element the element that is to be parsed into one or more {@code BeanDefinitions}
* @param parserContext the object encapsulating the current state of the parsing process
* @return the primary {@code BeanDefinition} (can be {@code null} as explained above)
*/
BeanDefinition parse(Element element, ParserContext parserContext);
/**
* Parse the specified {@link Node} and decorate the supplied
* {@link BeanDefinitionHolder}, returning the decorated definition.
* <p>The {@link Node} may be either an {@link org.w3c.dom.Attr} or an
* {@link Element}, depending on whether a custom attribute or element
* is being parsed.
* <p>Implementations may choose to return a completely new definition,
* which will replace the original definition in the resulting
* {@link org.springframework.beans.factory.BeanFactory}.
* <p>The supplied {@link ParserContext} can be used to register any
* additional beans needed to support the main definition.
* @param source the source element or attribute that is to be parsed
* @param definition the current bean definition
* @param parserContext the object encapsulating the current state of the parsing process
* @return the decorated definition (to be registered in the BeanFactory),
* or simply the original bean definition if no decoration is required.
* A {@code null} value is strictly speaking invalid, but will be leniently
* treated like the case where the original bean definition gets returned.
*/
BeanDefinitionHolder decorate(Node source, BeanDefinitionHolder definition, ParserContext parserContext);
}