org.springframework.web.struts.ContextLoaderPlugIn Maven / Gradle / Ivy
/*
* Copyright 2002-2005 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.struts;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.action.PlugIn;
import org.apache.struts.config.ModuleConfig;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.context.ApplicationContextException;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.util.StringUtils;
import org.springframework.web.context.ConfigurableWebApplicationContext;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.context.support.XmlWebApplicationContext;
/**
* Struts 1.1+ PlugIn that loads a Spring application context for the Struts
* ActionServlet. This context will automatically refer to the root
* WebApplicationContext (loaded by ContextLoaderListener/Servlet) as parent.
*
* The default namespace of the WebApplicationContext is the name of the
* Struts ActionServlet, suffixed with "-servlet" (e.g. "action-servlet").
* The default location of the XmlWebApplicationContext configuration file
* is therefore "/WEB-INF/action-servlet.xml".
*
*
* <plug-in className="org.springframework.web.struts.ContextLoaderPlugIn"/>
*
* The location of the context configuration files can be customized
* through the "contextConfigLocation" setting, analogous to the root
* WebApplicationContext and FrameworkServlet contexts.
*
*
* <plug-in className="org.springframework.web.struts.ContextLoaderPlugIn">
* <set-property property="contextConfigLocation" value="/WEB-INF/action-servlet.xml /WEB-INF/myContext.xml"/>
* </plug-in>
*
* Beans defined in the ContextLoaderPlugin context can be accessed
* from conventional Struts Actions, via fetching the WebApplicationContext
* reference from the ServletContext. ActionSupport and DispatchActionSupport
* are pre-built convenience classes that provide easy access to the context.
*
* It is normally preferable to access Spring's root WebApplicationContext
* in such scenarios, though: A shared middle tier should be defined there
* rather than in a ContextLoaderPlugin context, for access by any web component.
* ActionSupport and DispatchActionSupport auto-detect the root context too.
*
*
A special usage of this PlugIn is to define Struts Actions themselves
* as beans, typically wiring them with middle tier components defined in the
* root context. Such Actions will then be delegated to by proxy definitions
* in the Struts configuration, using the DelegatingActionProxy class or
* the DelegatingRequestProcessor.
*
*
Note that you can use a single ContextLoaderPlugIn for all Struts modules.
* That context can in turn be loaded from multiple XML files, for example split
* according to Struts modules. Alternatively, define one ContextLoaderPlugIn per
* Struts module, specifying appropriate "contextConfigLocation" parameters.
*
*
Note: The idea of delegating to Spring-managed Struts Actions originated in
* Don Brown's Spring Struts Plugin.
* ContextLoaderPlugIn and DelegatingActionProxy constitute a clean-room
* implementation of the same idea, essentially superseding the original plugin.
* Many thanks to Don Brown and Matt Raible for the original work, and for the
* agreement to reimplement the idea in standard Spring!
*
* @author Juergen Hoeller
* @since 1.0.1
* @see #SERVLET_CONTEXT_PREFIX
* @see ActionSupport
* @see DispatchActionSupport
* @see DelegatingActionProxy
* @see DelegatingRequestProcessor
* @see DelegatingTilesRequestProcessor
* @see org.springframework.web.context.ContextLoaderListener
* @see org.springframework.web.context.ContextLoaderServlet
* @see org.springframework.web.servlet.FrameworkServlet
*/
public class ContextLoaderPlugIn implements PlugIn {
/**
* Suffix for WebApplicationContext namespaces. If a Struts ActionServlet is
* given the name "action" in a context, the namespace used by this PlugIn will
* resolve to "action-servlet".
*/
public static final String DEFAULT_NAMESPACE_SUFFIX = "-servlet";
/**
* Default context class for ContextLoaderPlugIn.
* @see org.springframework.web.context.support.XmlWebApplicationContext
*/
public static final Class DEFAULT_CONTEXT_CLASS = XmlWebApplicationContext.class;
/**
* Prefix for the ServletContext attribute for the WebApplicationContext.
* The completion is the Struts module name.
*/
public static final String SERVLET_CONTEXT_PREFIX = ContextLoaderPlugIn.class.getName() + ".CONTEXT.";
protected final Log logger = LogFactory.getLog(getClass());
/** Custom WebApplicationContext class */
private Class contextClass = DEFAULT_CONTEXT_CLASS;
/** Namespace for this servlet */
private String namespace;
/** Explicit context config location */
private String contextConfigLocation;
/** The Struts ActionServlet that this PlugIn is registered with */
private ActionServlet actionServlet;
/** The Struts ModuleConfig that this PlugIn is registered with */
private ModuleConfig moduleConfig;
/** WebApplicationContext for the ActionServlet */
private WebApplicationContext webApplicationContext;
/**
* Set a custom context class by name. This class must be of type WebApplicationContext,
* when using the default ContextLoaderPlugIn implementation, the context class
* must also implement ConfigurableWebApplicationContext.
* @see #createWebApplicationContext
*/
public void setContextClassName(String contextClassName) throws ClassNotFoundException {
this.contextClass = Class.forName(contextClassName, true, Thread.currentThread().getContextClassLoader());
}
/**
* Set a custom context class. This class must be of type WebApplicationContext,
* when using the default ContextLoaderPlugIn implementation, the context class
* must also implement ConfigurableWebApplicationContext.
* @see #createWebApplicationContext
*/
public void setContextClass(Class contextClass) {
this.contextClass = contextClass;
}
/**
* Return the custom context class.
*/
public Class getContextClass() {
return contextClass;
}
/**
* Set a custom namespace for the ActionServlet,
* to be used for building a default context config location.
*/
public void setNamespace(String namespace) {
this.namespace = namespace;
}
/**
* Return the namespace for the ActionServlet, falling back to default scheme if
* no custom namespace was set: e.g. "test-servlet" for a servlet named "test".
*/
public String getNamespace() {
if (this.namespace != null) {
return this.namespace;
}
if (this.actionServlet != null) {
return this.actionServlet.getServletName() + DEFAULT_NAMESPACE_SUFFIX;
}
return null;
}
/**
* Set the context config location explicitly, instead of relying on the default
* location built from the namespace. This location string can consist of
* multiple locations separated by any number of commas and spaces.
*/
public void setContextConfigLocation(String contextConfigLocation) {
this.contextConfigLocation = contextConfigLocation;
}
/**
* Return the explicit context config location, if any.
*/
public String getContextConfigLocation() {
return contextConfigLocation;
}
/**
* Create the ActionServlet's WebApplicationContext.
*/
public final void init(ActionServlet actionServlet, ModuleConfig moduleConfig) throws ServletException {
long startTime = System.currentTimeMillis();
if (logger.isInfoEnabled()) {
logger.info("ContextLoaderPlugIn for Struts ActionServlet '" + actionServlet.getServletName() +
", module '" + moduleConfig.getPrefix() + "': initialization started");
}
this.actionServlet = actionServlet;
this.moduleConfig = moduleConfig;
try {
this.webApplicationContext = initWebApplicationContext();
onInit();
}
catch (RuntimeException ex) {
logger.error("Context initialization failed", ex);
throw ex;
}
if (logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
logger.info("ContextLoaderPlugIn for Struts ActionServlet '" + actionServlet.getServletName() +
"', module '" + moduleConfig.getPrefix() + "': initialization completed in " + elapsedTime + " ms");
}
}
/**
* Return the Struts ActionServlet that this PlugIn is associated with.
*/
public final ActionServlet getActionServlet() {
return actionServlet;
}
/**
* Return the name of the ActionServlet that this PlugIn is associated with.
*/
public final String getServletName() {
return this.actionServlet.getServletName();
}
/**
* Return the ServletContext that this PlugIn is associated with.
*/
public final ServletContext getServletContext() {
return this.actionServlet.getServletContext();
}
/**
* Return the Struts ModuleConfig that this PlugIn is associated with.
*/
public final ModuleConfig getModuleConfig() {
return moduleConfig;
}
/**
* Return the prefix of the ModuleConfig that this PlugIn is associated with.
* @see org.apache.struts.config.ModuleConfig#getPrefix
*/
public final String getModulePrefix() {
return this.moduleConfig.getPrefix();
}
/**
* Initialize and publish the WebApplicationContext for the ActionServlet.
* Delegates to createWebApplicationContext for actual creation.
*
Can be overridden in subclasses. Call getActionServlet
* and/or getModuleConfig to access the Struts configuration
* that this PlugIn is associated with.
* @throws org.springframework.beans.BeansException if the context couldn't be initialized
* @throws IllegalStateException if there is already a context for the Struts ActionServlet
* @see #createWebApplicationContext
* @see #getActionServlet
* @see #getServletName
* @see #getServletContext
* @see #getModuleConfig
* @see #getModulePrefix
*/
protected WebApplicationContext initWebApplicationContext() throws BeansException, IllegalStateException {
getServletContext().log("Initializing WebApplicationContext for Struts ActionServlet '" +
getServletName() + "', module '" + getModulePrefix() + "'");
WebApplicationContext parent = WebApplicationContextUtils.getWebApplicationContext(getServletContext());
WebApplicationContext wac = createWebApplicationContext(parent);
if (logger.isInfoEnabled()) {
logger.info("Using context class '" + wac.getClass().getName() + "' for servlet '" + getServletName() + "'");
}
// Publish the context as a servlet context attribute.
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);
if (logger.isDebugEnabled()) {
logger.debug("Published WebApplicationContext of Struts ActionServlet '" + getServletName() +
"', module '" + getModulePrefix() + "' as ServletContext attribute with name [" + attrName + "]");
}
return wac;
}
/**
* Instantiate the WebApplicationContext for the ActionServlet, either a default
* XmlWebApplicationContext or a custom context class if set. This implementation
* expects custom contexts to implement ConfigurableWebApplicationContext.
* Can be overridden in subclasses.
* @throws org.springframework.beans.BeansException if the context couldn't be initialized
* @see #setContextClass
* @see org.springframework.web.context.support.XmlWebApplicationContext
*/
protected WebApplicationContext createWebApplicationContext(WebApplicationContext parent)
throws BeansException {
if (logger.isDebugEnabled()) {
logger.debug("ContextLoaderPlugIn for Struts ActionServlet '" + getServletName() +
"', module '" + getModulePrefix() + "' will try to create custom WebApplicationContext " +
"context of class '" + getContextClass().getName() + "', using parent context [" + parent + "]");
}
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(getContextClass())) {
throw new ApplicationContextException(
"Fatal initialization error in ContextLoaderPlugIn for Struts ActionServlet '" + getServletName() +
"', module '" + getModulePrefix() + "': custom WebApplicationContext class [" +
getContextClass().getName() + "] is not of type ConfigurableWebApplicationContext");
}
ConfigurableWebApplicationContext wac =
(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(getContextClass());
wac.setParent(parent);
wac.setServletContext(getServletContext());
wac.setNamespace(getNamespace());
if (getContextConfigLocation() != null) {
wac.setConfigLocations(
StringUtils.tokenizeToStringArray(
getContextConfigLocation(), ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS));
}
wac.addBeanFactoryPostProcessor(
new BeanFactoryPostProcessor() {
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
beanFactory.addBeanPostProcessor(new ActionServletAwareProcessor(getActionServlet()));
}
}
);
wac.refresh();
return wac;
}
/**
* Return the ServletContext attribute name for this PlugIn's WebApplicationContext.
* Default implementation returns SERVLET_CONTEXT_PREFIX + module prefix.
* @see #SERVLET_CONTEXT_PREFIX
* @see #getModulePrefix
*/
public String getServletContextAttributeName() {
return SERVLET_CONTEXT_PREFIX + getModulePrefix();
}
/**
* Return this PlugIn's WebApplicationContext.
*/
public final WebApplicationContext getWebApplicationContext() {
return webApplicationContext;
}
/**
* Callback for custom initialization after the context has been set up.
* @throws ServletException if initialization failed
*/
protected void onInit() throws ServletException {
}
/**
* Close the WebApplicationContext of the ActionServlet.
* @see org.springframework.context.ConfigurableApplicationContext#close
*/
public void destroy() {
getServletContext().log("Closing WebApplicationContext of Struts ActionServlet '" +
getServletName() + "', module '" + getModulePrefix() + "'");
if (getWebApplicationContext() instanceof ConfigurableApplicationContext) {
((ConfigurableApplicationContext) getWebApplicationContext()).close();
}
}
}