org.springframework.web.struts.DelegatingActionUtils.java Source code

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/*
 * 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 org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.config.ModuleConfig;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

/**
 * Common methods for letting Struts Actions work with a
 * Spring WebApplicationContext.
 *
 * <p>As everything in Struts is based on concrete inheritance,
 * we have to provide an Action subclass (DelegatingActionProxy) and
 * two RequestProcessor subclasses (DelegatingRequestProcessor and
 * DelegatingTilesRequestProcessor). The only way to share common
 * functionality is a utility class like this one.
 *
 * @author Juergen Hoeller
 * @since 1.0.2
 * @see DelegatingActionProxy
 * @see DelegatingRequestProcessor
 * @see DelegatingTilesRequestProcessor
 */
public abstract class DelegatingActionUtils {

    protected static final Log logger = LogFactory.getLog(DelegatingActionUtils.class);

    /**
     * Fetch ContextLoaderPlugIn's WebApplicationContext from the ServletContext.
     * <p>Checks for a module-specific context first, falling back to the
     * context for the default module else.
     * @param actionServlet the associated ActionServlet
     * @param moduleConfig the associated ModuleConfig (can be <code>null</code>)
     * @return the WebApplicationContext, or <code>null</code> if none
     * @see ContextLoaderPlugIn#SERVLET_CONTEXT_PREFIX
     */
    public static WebApplicationContext getWebApplicationContext(ActionServlet actionServlet,
            ModuleConfig moduleConfig) {

        WebApplicationContext wac = null;
        String modulePrefix = null;

        // Try module-specific attribute.
        if (moduleConfig != null) {
            modulePrefix = moduleConfig.getPrefix();
            wac = (WebApplicationContext) actionServlet.getServletContext()
                    .getAttribute(ContextLoaderPlugIn.SERVLET_CONTEXT_PREFIX + modulePrefix);
        }

        // If not found, try attribute for default module.
        if (wac == null && !"".equals(modulePrefix)) {
            wac = (WebApplicationContext) actionServlet.getServletContext()
                    .getAttribute(ContextLoaderPlugIn.SERVLET_CONTEXT_PREFIX);
        }

        return wac;
    }

    /**
     * Fetch ContextLoaderPlugIn's WebApplicationContext from the ServletContext.
     * <p>Checks for a module-specific context first, falling back to the
     * context for the default module else.
     * @param actionServlet the associated ActionServlet
     * @param moduleConfig the associated ModuleConfig (can be <code>null</code>)
     * @return the WebApplicationContext
     * @throws IllegalStateException if no WebApplicationContext could be found
     * @see ContextLoaderPlugIn#SERVLET_CONTEXT_PREFIX
     */
    public static WebApplicationContext getRequiredWebApplicationContext(ActionServlet actionServlet,
            ModuleConfig moduleConfig) throws IllegalStateException {

        WebApplicationContext wac = getWebApplicationContext(actionServlet, moduleConfig);
        // If no Struts-specific context found, throw an exception.
        if (wac == null) {
            throw new IllegalStateException(
                    "Could not find ContextLoaderPlugIn's WebApplicationContext as ServletContext attribute ["
                            + ContextLoaderPlugIn.SERVLET_CONTEXT_PREFIX + "]: Did you register ["
                            + ContextLoaderPlugIn.class.getName() + "]?");
        }
        return wac;
    }

    /**
     * Find most specific context available: check ContextLoaderPlugIn's
     * WebApplicationContext first, fall back to root WebApplicationContext else.
     * <p>When checking the ContextLoaderPlugIn context: checks for a module-specific
     * context first, falling back to the context for the default module else.
     * @param actionServlet the associated ActionServlet
     * @param moduleConfig the associated ModuleConfig (can be <code>null</code>)
     * @return the WebApplicationContext
     * @throws IllegalStateException if no WebApplicationContext could be found
     * @see #getWebApplicationContext
     * @see org.springframework.web.context.support.WebApplicationContextUtils#getRequiredWebApplicationContext
     */
    public static WebApplicationContext findRequiredWebApplicationContext(ActionServlet actionServlet,
            ModuleConfig moduleConfig) throws IllegalStateException {

        WebApplicationContext wac = getWebApplicationContext(actionServlet, moduleConfig);
        // If no Struts-specific context found, fall back to root context.
        if (wac == null) {
            wac = WebApplicationContextUtils.getRequiredWebApplicationContext(actionServlet.getServletContext());
        }
        return wac;
    }

    /**
     * Default implementation of Action bean determination, taking
     * the mapping path and prepending the module prefix, if any.
     * @param mapping the Struts ActionMapping
     * @return the name of the Action bean
     * @see org.apache.struts.action.ActionMapping#getPath
     * @see org.apache.struts.config.ModuleConfig#getPrefix
     */
    public static String determineActionBeanName(ActionMapping mapping) {
        String prefix = mapping.getModuleConfig().getPrefix();
        String path = mapping.getPath();
        String beanName = prefix + path;
        if (logger.isDebugEnabled()) {
            logger.debug("DelegatingActionProxy with mapping path '" + path + "' and module prefix '" + prefix
                    + "' delegating to Spring bean with name [" + beanName + "]");
        }
        return beanName;
    }

}