infra.beans.factory.xml.AbstractBeanDefinitionParser Maven / Gradle / Ivy
/*
* Copyright 2017 - 2024 the original author or authors.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see [https://www.gnu.org/licenses/]
*/
package infra.beans.factory.xml;
import org.w3c.dom.Element;
import infra.beans.factory.BeanDefinitionStoreException;
import infra.beans.factory.config.BeanDefinition;
import infra.beans.factory.config.BeanDefinitionHolder;
import infra.beans.factory.parsing.BeanComponentDefinition;
import infra.beans.factory.parsing.ReaderContext;
import infra.beans.factory.support.AbstractBeanDefinition;
import infra.beans.factory.support.BeanDefinitionReaderUtils;
import infra.beans.factory.support.BeanDefinitionRegistry;
import infra.lang.Nullable;
import infra.util.StringUtils;
/**
* Abstract {@link BeanDefinitionParser} implementation providing
* a number of convenience methods and a
* {@link AbstractBeanDefinitionParser#parseInternal template method}
* that subclasses must override to provide the actual parsing logic.
*
* Use this {@link BeanDefinitionParser} implementation when you want
* to parse some arbitrarily complex XML into one or more
* {@link BeanDefinition BeanDefinitions}. If you just want to parse some
* XML into a single {@code BeanDefinition}, you may wish to consider
* the simpler convenience extensions of this class, namely
* {@link AbstractSingleBeanDefinitionParser} and
* {@link AbstractSimpleBeanDefinitionParser}.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Rick Evans
* @author Dave Syer
* @since 4.0
*/
public abstract class AbstractBeanDefinitionParser implements BeanDefinitionParser {
/** Constant for the "id" attribute. */
public static final String ID_ATTRIBUTE = "id";
/** Constant for the "name" attribute. */
public static final String NAME_ATTRIBUTE = "name";
@Override
@Nullable
public final BeanDefinition parse(Element element, ParserContext parserContext) {
AbstractBeanDefinition definition = parseInternal(element, parserContext);
if (definition != null && !parserContext.isNested()) {
try {
String id = resolveId(element, definition, parserContext);
if (StringUtils.isBlank(id)) {
parserContext.getReaderContext().error(
"Id is required for element '" + parserContext.getDelegate().getLocalName(element)
+ "' when used as a top-level tag", element);
}
String[] aliases = null;
if (shouldParseNameAsAliases()) {
String name = element.getAttribute(NAME_ATTRIBUTE);
if (StringUtils.isNotEmpty(name)) {
aliases = StringUtils.trimArrayElements(StringUtils.commaDelimitedListToStringArray(name));
}
}
BeanDefinitionHolder holder = new BeanDefinitionHolder(definition, id, aliases);
registerBeanDefinition(holder, parserContext.getRegistry());
if (shouldFireEvents()) {
BeanComponentDefinition componentDefinition = new BeanComponentDefinition(holder);
postProcessComponentDefinition(componentDefinition);
parserContext.registerComponent(componentDefinition);
}
}
catch (BeanDefinitionStoreException ex) {
String msg = ex.getMessage();
parserContext.getReaderContext().error((msg != null ? msg : ex.toString()), element);
return null;
}
}
return definition;
}
/**
* Resolve the ID for the supplied {@link BeanDefinition}.
*
When using {@link #shouldGenerateId generation}, a name is generated automatically.
* Otherwise, the ID is extracted from the "id" attribute, potentially with a
* {@link #shouldGenerateIdAsFallback() fallback} to a generated id.
*
* @param element the element that the bean definition has been built from
* @param definition the bean definition to be registered
* @param parserContext the object encapsulating the current state of the parsing process;
* provides access to a {@link BeanDefinitionRegistry}
* @return the resolved id
* @throws BeanDefinitionStoreException if no unique name could be generated
* for the given bean definition
*/
protected String resolveId(Element element, AbstractBeanDefinition definition, ParserContext parserContext)
throws BeanDefinitionStoreException {
if (shouldGenerateId()) {
return parserContext.getReaderContext().generateBeanName(definition);
}
else {
String id = element.getAttribute(ID_ATTRIBUTE);
if (StringUtils.isBlank(id) && shouldGenerateIdAsFallback()) {
id = parserContext.getReaderContext().generateBeanName(definition);
}
return id;
}
}
/**
* Register the supplied {@link BeanDefinition bean} with the supplied
* {@link BeanDefinitionRegistry registry}.
*
Subclasses can override this method to control whether or not the supplied
* {@link BeanDefinition bean} is actually even registered, or to
* register even more beans.
*
The default implementation registers the supplied {@link BeanDefinition bean}
* with the supplied {@link BeanDefinitionRegistry registry} only if the {@code isNested}
* parameter is {@code false}, because one typically does not want inner beans
* to be registered as top level beans.
*
* @param definition the bean definition to be registered
* @param registry the registry that the bean is to be registered with
* @see BeanDefinitionReaderUtils#registerBeanDefinition(BeanDefinitionHolder, BeanDefinitionRegistry)
*/
protected void registerBeanDefinition(BeanDefinitionHolder definition, BeanDefinitionRegistry registry) {
BeanDefinitionReaderUtils.registerBeanDefinition(definition, registry);
}
/**
* Central template method to actually parse the supplied {@link Element}
* into one or more {@link BeanDefinition BeanDefinitions}.
*
* @param element the element that is to be parsed into one or more {@link BeanDefinition BeanDefinitions}
* @param parserContext the object encapsulating the current state of the parsing process;
* provides access to a {@link BeanDefinitionRegistry}
* @return the primary {@link BeanDefinition} resulting from the parsing of the supplied {@link Element}
* @see #parse(Element, ParserContext)
* @see #postProcessComponentDefinition(BeanComponentDefinition)
*/
@Nullable
protected abstract AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext);
/**
* Should an ID be generated instead of read from the passed in {@link Element}?
*
Disabled by default; subclasses can override this to enable ID generation.
* Note that this flag is about always generating an ID; the parser
* won't even check for an "id" attribute in this case.
*
* @return whether the parser should always generate an id
*/
protected boolean shouldGenerateId() {
return false;
}
/**
* Should an ID be generated instead if the passed in {@link Element} does not
* specify an "id" attribute explicitly?
*
Disabled by default; subclasses can override this to enable ID generation
* as fallback: The parser will first check for an "id" attribute in this case,
* only falling back to a generated ID if no value was specified.
*
* @return whether the parser should generate an id if no id was specified
*/
protected boolean shouldGenerateIdAsFallback() {
return false;
}
/**
* Determine whether the element's "name" attribute should get parsed as
* bean definition aliases, i.e. alternative bean definition names.
*
The default implementation returns {@code true}.
*
* @return whether the parser should evaluate the "name" attribute as aliases
*/
protected boolean shouldParseNameAsAliases() {
return true;
}
/**
* Determine whether this parser is supposed to fire a
* {@link BeanComponentDefinition}
* event after parsing the bean definition.
*
This implementation returns {@code true} by default; that is,
* an event will be fired when a bean definition has been completely parsed.
* Override this to return {@code false} in order to suppress the event.
*
* @return {@code true} in order to fire a component registration event
* after parsing the bean definition; {@code false} to suppress the event
* @see #postProcessComponentDefinition
* @see ReaderContext#fireComponentRegistered
*/
protected boolean shouldFireEvents() {
return true;
}
/**
* Hook method called after the primary parsing of a
* {@link BeanComponentDefinition} but before the
* {@link BeanComponentDefinition} has been registered with a
* {@link BeanDefinitionRegistry}.
*
Derived classes can override this method to supply any custom logic that
* is to be executed after all the parsing is finished.
*
The default implementation is a no-op.
*
* @param componentDefinition the {@link BeanComponentDefinition} that is to be processed
*/
protected void postProcessComponentDefinition(BeanComponentDefinition componentDefinition) {
}
}