/*
 * 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.struts;

import java.io.File;

import javax.servlet.ServletContext;

import org.apache.struts.action.ActionServlet;
import org.apache.struts.actions.MappingDispatchAction;

import org.springframework.context.support.MessageSourceAccessor;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
import org.springframework.web.util.WebUtils;

/**
 * Convenience class for Spring-aware Struts 1.2 MappingDispatchActions.
 *
 * <p>Provides a reference to the current Spring application context, e.g.
 * for bean lookup or resource loading. Auto-detects a ContextLoaderPlugIn
 * context, falling back to the root WebApplicationContext. For typical
 * usage, i.e. accessing middle tier beans, use a root WebApplicationContext.
 *
 * <p>For classic Struts Actions, DispatchActions or LookupDispatchActions,
 * use the analogous {@link ActionSupport ActionSupport} or
 * {@link DispatchActionSupport DispatchActionSupport} /
 * {@link LookupDispatchActionSupport LookupDispatchActionSupport} class.
 *
 * <p>As an alternative approach, you can wire your Struts Actions themselves
 * as Spring beans, passing references to them via IoC rather than looking
 * up references in a programmatic fashion. Check out
 * {@link DelegatingActionProxy DelegatingActionProxy} and
 * {@link DelegatingRequestProcessor DelegatingRequestProcessor}.
 *
 * @author Juergen Hoeller
 * @since 1.1.3
 * @see ContextLoaderPlugIn#SERVLET_CONTEXT_PREFIX
 * @see WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE
 * @see org.springframework.web.context.ContextLoaderListener
 * @see org.springframework.web.context.ContextLoaderServlet
 * @see ActionSupport
 * @see DispatchActionSupport
 * @see LookupDispatchActionSupport
 * @see DelegatingActionProxy
 * @see DelegatingRequestProcessor
 */
public abstract class MappingDispatchActionSupport extends MappingDispatchAction {

	private WebApplicationContext webApplicationContext;

	private MessageSourceAccessor messageSourceAccessor;

	/**
	 * Initialize the WebApplicationContext for this Action.
	 * Invokes onInit after successful initialization of the context.
	 * @see #initWebApplicationContext
	 * @see #onInit
	 */
	public void setServlet(ActionServlet actionServlet) {
		super.setServlet(actionServlet);
		if (actionServlet != null) {
			this.webApplicationContext = initWebApplicationContext(actionServlet);
			this.messageSourceAccessor = new MessageSourceAccessor(this.webApplicationContext);
			onInit();
		}
		else {
			onDestroy();
		}
	}

	/**
	 * Fetch ContextLoaderPlugIn's WebApplicationContext from the ServletContext,
	 * falling back to the root WebApplicationContext (the usual case).
	 * @param actionServlet the associated ActionServlet
	 * @return the WebApplicationContext
	 * @throws IllegalStateException if no WebApplicationContext could be found
	 * @see ContextLoaderPlugIn#SERVLET_CONTEXT_PREFIX
	 * @see WebApplicationContextUtils#getWebApplicationContext
	 */
	protected WebApplicationContext initWebApplicationContext(ActionServlet actionServlet)
			throws IllegalStateException {
		ServletContext sc = actionServlet.getServletContext();
		WebApplicationContext wac = (WebApplicationContext)
				sc.getAttribute(ContextLoaderPlugIn.SERVLET_CONTEXT_PREFIX);
		if (wac == null) {
			wac = WebApplicationContextUtils.getRequiredWebApplicationContext(sc);
		}
		return wac;
	}

	/**
	 * Return the current Spring WebApplicationContext.
	 */
	protected final WebApplicationContext getWebApplicationContext() {
		return this.webApplicationContext;
	}

	/**
	 * Return a MessageSourceAccessor for the application context
	 * used by this object, for easy message access.
	 */
	protected final MessageSourceAccessor getMessageSourceAccessor() {
		return this.messageSourceAccessor;
	}

	/**
	 * Return the current ServletContext.
	 */
	protected final ServletContext getServletContext() {
		return this.webApplicationContext.getServletContext();
	}

	/**
	 * Return the temporary directory for the current web application,
	 * as provided by the servlet container.
	 * @return the File representing the temporary directory
	 */
	protected final File getTempDir() {
		return WebUtils.getTempDir(getServletContext());
	}

	/**
	 * Callback for custom initialization after the context has been set up.
	 * @see #setServlet
	 */
	protected void onInit() {
	}

	/**
	 * Callback for custom destruction when the ActionServlet shuts down.
	 * @see #setServlet
	 */
	protected void onDestroy() {
	}

}
