/*
 * Copyright 2002-2018 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.web.context.support;

import java.io.IOException;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.beans.factory.xml.ResourceEntityResolver;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;

WebApplicationContext implementation which takes its configuration from XML documents, understood by an XmlBeanDefinitionReader. This is essentially the equivalent of GenericXmlApplicationContext for a web environment. 
By default, the configuration will be taken from "/WEB-INF/applicationContext.xml"
for the root context, and "/WEB-INF/test-servlet.xml" for a context with the namespace
"test-servlet" (like for a DispatcherServlet instance with the servlet-name "test").
The config location defaults can be overridden via the "contextConfigLocation" context-param of ContextLoader and servlet init-param of FrameworkServlet. Config locations can either denote concrete files like "/WEB-INF/context.xml" or Ant-style patterns like "/WEB-INF/*-context.xml" (see PathMatcher javadoc for pattern details). 
Note: In case of multiple config locations, later bean definitions will
override ones defined in earlier loaded files. This can be leveraged to
deliberately override certain bean definitions via an extra XML file.
For a WebApplicationContext that reads in a different bean definition format, create an analogous subclass of AbstractRefreshableWebApplicationContext.
Such a context implementation can be specified as "contextClass" context-param
for ContextLoader or "contextClass" init-param for FrameworkServlet.
Author:
Rod Johnson, Juergen Hoeller
See Also:
AbstractRefreshableWebApplicationContext.setNamespace
AbstractRefreshableConfigApplicationContext.setConfigLocations
XmlBeanDefinitionReader
ContextLoader.initWebApplicationContext
initWebApplicationContext.initWebApplicationContext/**
 * {@link org.springframework.web.context.WebApplicationContext} implementation
 * which takes its configuration from XML documents, understood by an
 * {@link org.springframework.beans.factory.xml.XmlBeanDefinitionReader}.
 * This is essentially the equivalent of
 * {@link org.springframework.context.support.GenericXmlApplicationContext}
 * for a web environment.
 *
 * <p>By default, the configuration will be taken from "/WEB-INF/applicationContext.xml"
 * for the root context, and "/WEB-INF/test-servlet.xml" for a context with the namespace
 * "test-servlet" (like for a DispatcherServlet instance with the servlet-name "test").
 *
 * <p>The config location defaults can be overridden via the "contextConfigLocation"
 * context-param of {@link org.springframework.web.context.ContextLoader} and servlet
 * init-param of {@link org.springframework.web.servlet.FrameworkServlet}. Config locations
 * can either denote concrete files like "/WEB-INF/context.xml" or Ant-style patterns
 * like "/WEB-INF/*-context.xml" (see {@link org.springframework.util.PathMatcher}
 * javadoc for pattern details).
 *
 * <p>Note: In case of multiple config locations, later bean definitions will
 * override ones defined in earlier loaded files. This can be leveraged to
 * deliberately override certain bean definitions via an extra XML file.
 *
 * <p><b>For a WebApplicationContext that reads in a different bean definition format,
 * create an analogous subclass of {@link AbstractRefreshableWebApplicationContext}.</b>
 * Such a context implementation can be specified as "contextClass" context-param
 * for ContextLoader or "contextClass" init-param for FrameworkServlet.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see #setNamespace
 * @see #setConfigLocations
 * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
 * @see org.springframework.web.context.ContextLoader#initWebApplicationContext
 * @see org.springframework.web.servlet.FrameworkServlet#initWebApplicationContext
 */
public class XmlWebApplicationContext extends AbstractRefreshableWebApplicationContext {

	
Default config location for the root context. /** Default config location for the root context. */
	public static final String DEFAULT_CONFIG_LOCATION = "/WEB-INF/applicationContext.xml";

	
Default prefix for building a config location for a namespace. /** Default prefix for building a config location for a namespace. */
	public static final String DEFAULT_CONFIG_LOCATION_PREFIX = "/WEB-INF/";

	
Default suffix for building a config location for a namespace. /** Default suffix for building a config location for a namespace. */
	public static final String DEFAULT_CONFIG_LOCATION_SUFFIX = ".xml";


	
Loads the bean definitions via an XmlBeanDefinitionReader.
See Also:
XmlBeanDefinitionReader
initBeanDefinitionReader
loadBeanDefinitions/**
	 * Loads the bean definitions via an XmlBeanDefinitionReader.
	 * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader
	 * @see #initBeanDefinitionReader
	 * @see #loadBeanDefinitions
	 */
	@Override
	protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
		// Create a new XmlBeanDefinitionReader for the given BeanFactory.
		XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

		// Configure the bean definition reader with this context's
		// resource loading environment.
		beanDefinitionReader.setEnvironment(getEnvironment());
		beanDefinitionReader.setResourceLoader(this);
		beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

		// Allow a subclass to provide custom initialization of the reader,
		// then proceed with actually loading the bean definitions.
		initBeanDefinitionReader(beanDefinitionReader);
		loadBeanDefinitions(beanDefinitionReader);
	}

	
Initialize the bean definition reader used for loading the bean
definitions of this context. Default implementation is empty.
Can be overridden in subclasses, e.g. for turning off XML validation
or using a different XmlBeanDefinitionParser implementation.
Params:
beanDefinitionReader – the bean definition reader used by this context
See Also:
XmlBeanDefinitionReader.setValidationMode
XmlBeanDefinitionReader.setDocumentReaderClass/**
	 * Initialize the bean definition reader used for loading the bean
	 * definitions of this context. Default implementation is empty.
	 * <p>Can be overridden in subclasses, e.g. for turning off XML validation
	 * or using a different XmlBeanDefinitionParser implementation.
	 * @param beanDefinitionReader the bean definition reader used by this context
	 * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader#setValidationMode
	 * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader#setDocumentReaderClass
	 */
	protected void initBeanDefinitionReader(XmlBeanDefinitionReader beanDefinitionReader) {
	}

	
Load the bean definitions with the given XmlBeanDefinitionReader.
The lifecycle of the bean factory is handled by the refreshBeanFactory method;
therefore this method is just supposed to load and/or register bean definitions.
Delegates to a ResourcePatternResolver for resolving location patterns
into Resource instances.
Throws:
IOException – if the required XML document isn't found
See Also:
AbstractRefreshableApplicationContext.refreshBeanFactory
AbstractRefreshableWebApplicationContext.getConfigLocations
AbstractApplicationContext.getResources
AbstractRefreshableWebApplicationContext.getResourcePatternResolver/**
	 * Load the bean definitions with the given XmlBeanDefinitionReader.
	 * <p>The lifecycle of the bean factory is handled by the refreshBeanFactory method;
	 * therefore this method is just supposed to load and/or register bean definitions.
	 * <p>Delegates to a ResourcePatternResolver for resolving location patterns
	 * into Resource instances.
	 * @throws IOException if the required XML document isn't found
	 * @see #refreshBeanFactory
	 * @see #getConfigLocations
	 * @see #getResources
	 * @see #getResourcePatternResolver
	 */
	protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws IOException {
		String[] configLocations = getConfigLocations();
		if (configLocations != null) {
			for (String configLocation : configLocations) {
				reader.loadBeanDefinitions(configLocation);
			}
		}
	}

	
The default location for the root context is "/WEB-INF/applicationContext.xml",
and "/WEB-INF/test-servlet.xml" for a context with the namespace "test-servlet"
(like for a DispatcherServlet instance with the servlet-name "test").
/**
	 * The default location for the root context is "/WEB-INF/applicationContext.xml",
	 * and "/WEB-INF/test-servlet.xml" for a context with the namespace "test-servlet"
	 * (like for a DispatcherServlet instance with the servlet-name "test").
	 */
	@Override
	protected String[] getDefaultConfigLocations() {
		if (getNamespace() != null) {
			return new String[] {DEFAULT_CONFIG_LOCATION_PREFIX + getNamespace() + DEFAULT_CONFIG_LOCATION_SUFFIX};
		}
		else {
			return new String[] {DEFAULT_CONFIG_LOCATION};
		}
	}

}