org.springframework.web.context.ContextLoader Maven / Gradle / Ivy
/*
* Copyright 2002-2004 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;
import javax.servlet.ServletContext;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextException;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.util.StringUtils;
import org.springframework.web.context.support.XmlWebApplicationContext;
/**
* Performs the actual initialization work for the root application context.
* Called by ContextLoaderListener and ContextLoaderServlet.
*
* Regards a "contextClass" parameter at the web.xml context-param level,
* falling back to the default context class (XmlWebApplicationContext) if not found.
* With the default ContextLoader, a context class needs to implement
* ConfigurableWebApplicationContext.
*
*
Passes a "contextConfigLocation" context-param to the context instance,
* parsing it into potentially multiple file paths which can be separated by any
* number of commas and spaces, like "applicationContext1.xml, applicationContext2.xml".
* If not explicitly specified, the context implementation is supposed to use a
* default location (with XmlWebApplicationContext: "/WEB-INF/applicationContext.xml").
*
*
Note: In case of multiple config locations, later bean definitions will
* override ones defined in earlier loaded files, at least when using one of
* Spring's default ApplicationContext implementations. This can be leveraged
* to deliberately override certain bean definitions via an extra XML file.
*
* @author Juergen Hoeller
* @author Colin Sampaleanu
* @since 17.02.2003
* @see ContextLoaderListener
* @see ContextLoaderServlet
* @see ConfigurableWebApplicationContext
* @see org.springframework.web.context.support.XmlWebApplicationContext
*/
public class ContextLoader {
/**
* Config param for the root WebApplicationContext implementation class to use:
* "contextClass"
*/
public static final String CONTEXT_CLASS_PARAM = "contextClass";
/**
* Default context class for ContextLoader.
* @see org.springframework.web.context.support.XmlWebApplicationContext
*/
public static final Class DEFAULT_CONTEXT_CLASS = XmlWebApplicationContext.class;
/**
* Name of servlet context parameter that can specify the config location
* for the root context, falling back to the implementation's default else.
* @see org.springframework.web.context.support.XmlWebApplicationContext#DEFAULT_CONFIG_LOCATION
*/
public static final String CONFIG_LOCATION_PARAM = "contextConfigLocation";
private final Log logger = LogFactory.getLog(ContextLoader.class);
/**
* Initialize Spring's web application context for the given servlet context,
* regarding the "contextClass" and "contextConfigLocation" context-params.
* @param servletContext current servlet context
* @return the new WebApplicationContext
* @throws BeansException if the context couldn't be initialized
* @see #CONTEXT_CLASS_PARAM
* @see #CONFIG_LOCATION_PARAM
*/
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) throws BeansException {
servletContext.log("Loading root WebApplicationContext");
try {
ApplicationContext parent = loadParentContext(servletContext);
WebApplicationContext wac = createWebApplicationContext(servletContext, parent);
logger.info("Using context class [" + wac.getClass().getName() + "] for root WebApplicationContext");
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, wac);
if (logger.isInfoEnabled()) {
logger.info("Published root WebApplicationContext [" + wac +
"] as ServletContext attribute with name [" +
WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
}
return wac;
}
catch (RuntimeException ex) {
logger.error("Context initialization failed", ex);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
throw ex;
}
catch (Error err) {
logger.error("Context initialization failed", err);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
throw err;
}
}
/**
* Instantiate the root WebApplicationContext for this loader, either a default
* XmlWebApplicationContext or a custom context class if specified.
* This implementation expects custom contexts to implement ConfigurableWebApplicationContext.
* Can be overridden in subclasses.
* @throws BeansException if the context couldn't be initialized
* @see #CONTEXT_CLASS_PARAM
* @see #DEFAULT_CONTEXT_CLASS
* @see ConfigurableWebApplicationContext
* @see org.springframework.web.context.support.XmlWebApplicationContext
*/
protected WebApplicationContext createWebApplicationContext(ServletContext servletContext, ApplicationContext parent)
throws BeansException {
String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);
Class contextClass = DEFAULT_CONTEXT_CLASS;
if (contextClassName != null) {
try {
contextClass = Class.forName(contextClassName, true, Thread.currentThread().getContextClassLoader());
}
catch (ClassNotFoundException ex) {
throw new ApplicationContextException("Failed to load context class [" + contextClassName + "]", ex);
}
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
throw new ApplicationContextException(
"Custom context class [" + contextClassName + "] is not of type ConfigurableWebApplicationContext");
}
}
ConfigurableWebApplicationContext wac =
(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
wac.setParent(parent);
wac.setServletContext(servletContext);
String configLocation = servletContext.getInitParameter(CONFIG_LOCATION_PARAM);
if (configLocation != null) {
wac.setConfigLocations(
StringUtils.tokenizeToStringArray(
configLocation, ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS, true, true));
}
wac.refresh();
return wac;
}
/**
* Template method which may be overridden by a subclass to load or obtain
* an ApplicationContext instance which will be used as the parent context
* of the root WebApplicationContext if it is not null.
* @param servletContext
* @return the parent application context, or null if none
* @throws BeansException if the context couldn't be initialized
*/
protected ApplicationContext loadParentContext(ServletContext servletContext) throws BeansException {
return null;
}
/**
* Close Spring's web application context for the given servlet context.
* @param servletContext current servlet context
*/
public void closeWebApplicationContext(ServletContext servletContext) throws ApplicationContextException {
servletContext.log("Closing root WebApplicationContext");
Object wac = servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
if (wac instanceof ConfigurableApplicationContext) {
((ConfigurableApplicationContext) wac).close();
}
}
}