/*
* Copyright 2002-2010 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 java.io.IOException;
import java.net.URISyntaxException;
import java.util.LinkedHashSet;
import java.util.Set;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.springframework.beans.factory.BeanDefinitionStoreException;
import org.springframework.beans.factory.config.BeanDefinitionHolder;
import org.springframework.beans.factory.parsing.BeanComponentDefinition;
import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.ResourcePatternUtils;
import org.springframework.util.ResourceUtils;
import org.springframework.util.StringUtils;
import org.springframework.util.SystemPropertyUtils;
/**
* Default implementation of the {@link BeanDefinitionDocumentReader} interface.
* Reads bean definitions according to the "spring-beans" DTD and XSD format
* (Spring's default XML bean definition format).
*
* <p>The structure, elements and attribute names of the required XML document
* are hard-coded in this class. (Of course a transform could be run if necessary
* to produce this format). <code><beans></code> doesn't need to be the root
* element of the XML document: This class will parse all bean definition elements
* in the XML file, not regarding the actual root element.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Rob Harrop
* @author Erik Wiersma
* @since 18.12.2003
*/
public class DefaultBeanDefinitionDocumentReader implements BeanDefinitionDocumentReader {
public static final String BEAN_ELEMENT = BeanDefinitionParserDelegate.BEAN_ELEMENT;
public static final String ALIAS_ELEMENT = "alias";
public static final String NAME_ATTRIBUTE = "name";
public static final String ALIAS_ATTRIBUTE = "alias";
public static final String IMPORT_ELEMENT = "import";
public static final String RESOURCE_ATTRIBUTE = "resource";
protected final Log logger = LogFactory.getLog(getClass());
private XmlReaderContext readerContext;
/**
* Parses bean definitions according to the "spring-beans" DTD.
* <p>Opens a DOM Document; then initializes the default settings
* specified at <code><beans></code> level; then parses
* the contained bean definitions.
*/
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
BeanDefinitionParserDelegate delegate = createHelper(readerContext, root);
preProcessXml(root);
parseBeanDefinitions(root, delegate);
postProcessXml(root);
}
protected BeanDefinitionParserDelegate createHelper(XmlReaderContext readerContext, Element root) {
BeanDefinitionParserDelegate delegate = new BeanDefinitionParserDelegate(readerContext);
delegate.initDefaults(root);
return delegate;
}
/**
* Return the descriptor for the XML resource that this parser works on.
*/
protected final XmlReaderContext getReaderContext() {
return this.readerContext;
}
/**
* Invoke the {@link org.springframework.beans.factory.parsing.SourceExtractor} to pull the
* source metadata from the supplied {@link Element}.
*/
protected Object extractSource(Element ele) {
return this.readerContext.extractSource(ele);
}
/**
* Parse the elements at the root level in the document:
* "import", "alias", "bean".
* @param root the DOM root element of the document
*/
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
if (delegate.isDefaultNamespace(root)) {
NodeList nl = root.getChildNodes();
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element) {
Element ele = (Element) node;
if (delegate.isDefaultNamespace(ele)) {
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
}
/**
* Parse an "import" element and load the bean definitions
* from the given resource into the bean factory.
*/
protected void importBeanDefinitionResource(Element ele) {
String location = ele.getAttribute(RESOURCE_ATTRIBUTE);
if (!StringUtils.hasText(location)) {
getReaderContext().error("Resource location must not be empty", ele);
return;
}
// Resolve system properties: e.g. "${user.dir}"
location = SystemPropertyUtils.resolvePlaceholders(location);
Set<Resource> actualResources = new LinkedHashSet<Resource>(4);
// Discover whether the location is an absolute or relative URI
boolean absoluteLocation = false;
try {
absoluteLocation = ResourcePatternUtils.isUrl(location) || ResourceUtils.toURI(location).isAbsolute();
}
catch (URISyntaxException ex) {
// cannot convert to an URI, considering the location relative
// unless it is the well-known Spring prefix "classpath*:"
}
// Absolute or relative?
if (absoluteLocation) {
try {
int importCount = getReaderContext().getReader().loadBeanDefinitions(location, actualResources);
if (logger.isDebugEnabled()) {
logger.debug("Imported " + importCount + " bean definitions from URL location [" + location + "]");
}
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error(
"Failed to import bean definitions from URL location [" + location + "]", ele, ex);
}
}
else {
// No URL -> considering resource location as relative to the current file.
try {
int importCount;
Resource relativeResource = getReaderContext().getResource().createRelative(location);
if (relativeResource.exists()) {
importCount = getReaderContext().getReader().loadBeanDefinitions(relativeResource);
actualResources.add(relativeResource);
}
else {
String baseLocation = getReaderContext().getResource().getURL().toString();
importCount = getReaderContext().getReader().loadBeanDefinitions(
StringUtils.applyRelativePath(baseLocation, location), actualResources);
}
if (logger.isDebugEnabled()) {
logger.debug("Imported " + importCount + " bean definitions from relative location [" + location + "]");
}
}
catch (IOException ex) {
getReaderContext().error("Failed to resolve current resource location", ele, ex);
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to import bean definitions from relative location [" + location + "]",
ele, ex);
}
}
Resource[] actResArray = actualResources.toArray(new Resource[actualResources.size()]);
getReaderContext().fireImportProcessed(location, actResArray, extractSource(ele));
}
/**
* Process the given alias element, registering the alias with the registry.
*/
protected void processAliasRegistration(Element ele) {
String name = ele.getAttribute(NAME_ATTRIBUTE);
String alias = ele.getAttribute(ALIAS_ATTRIBUTE);
boolean valid = true;
if (!StringUtils.hasText(name)) {
getReaderContext().error("Name must not be empty", ele);
valid = false;
}
if (!StringUtils.hasText(alias)) {
getReaderContext().error("Alias must not be empty", ele);
valid = false;
}
if (valid) {
try {
getReaderContext().getRegistry().registerAlias(name, alias);
}
catch (Exception ex) {
getReaderContext().error("Failed to register alias '" + alias +
"' for bean with name '" + name + "'", ele, ex);
}
getReaderContext().fireAliasRegistered(name, alias, extractSource(ele));
}
}
/**
* Process the given bean element, parsing the bean definition
* and registering it with the registry.
*/
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}
/**
* Allow the XML to be extensible by processing any custom element types first,
* before we start to process the bean definitions. This method is a natural
* extension point for any other custom pre-processing of the XML.
* <p>The default implementation is empty. Subclasses can override this method to
* convert custom elements into standard Spring bean definitions, for example.
* Implementors have access to the parser's bean definition reader and the
* underlying XML resource, through the corresponding accessors.
* @see #getReaderContext()
*/
protected void preProcessXml(Element root) {
}
/**
* Allow the XML to be extensible by processing any custom element types last,
* after we finished processing the bean definitions. This method is a natural
* extension point for any other custom post-processing of the XML.
* <p>The default implementation is empty. Subclasses can override this method to
* convert custom elements into standard Spring bean definitions, for example.
* Implementors have access to the parser's bean definition reader and the
* underlying XML resource, through the corresponding accessors.
* @see #getReaderContext()
*/
protected void postProcessXml(Element root) {
}
}
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