/*
* Copyright 2002-2007 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.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.config.ModuleConfig;
import org.springframework.beans.BeansException;
import org.springframework.web.context.WebApplicationContext;
/**
* Proxy for a Spring-managed Struts <code>Action</code> that is defined in
* {@link ContextLoaderPlugIn ContextLoaderPlugIn's}
* {@link WebApplicationContext}.
*
* <p>The proxy is defined in the Struts config file, specifying this
* class as the action class. This class will delegate to a Struts
* <code>Action</code> bean in the <code>ContextLoaderPlugIn</code> context.
*
* <pre class="code"><action path="/login" type="org.springframework.web.struts.DelegatingActionProxy"/></pre>
*
* The name of the <code>Action</code> bean in the
* <code>WebApplicationContext</code> will be determined from the mapping
* path and module prefix. This can be customized by overriding the
* <code>determineActionBeanName</code> method.
*
* <p>Example:
* <ul>
* <li>mapping path "/login" -> bean name "/login"<br>
* <li>mapping path "/login", module prefix "/mymodule" ->
* bean name "/mymodule/login"
* </ul>
*
* <p>A corresponding bean definition in the <code>ContextLoaderPlugin</code>
* context would look as follows; notice that the <code>Action</code> is now
* able to leverage fully Spring's configuration facilities:
*
* <pre class="code">
* <bean name="/login" class="myapp.MyAction">
* <property name="...">...</property>
* </bean></pre>
*
* Note that you can use a single <code>ContextLoaderPlugIn</code> 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
* <code>ContextLoaderPlugIn</code> per Struts module, specifying appropriate
* "contextConfigLocation" parameters. In both cases, the Spring bean name
* has to include the module prefix.
*
* <p>If you want to avoid having to specify <code>DelegatingActionProxy</code>
* as the <code>Action</code> type in your struts-config file (for example to
* be able to generate your Struts config file with XDoclet) consider using the
* {@link DelegatingRequestProcessor DelegatingRequestProcessor}.
* The latter's disadvantage is that it might conflict with the need
* for a different <code>RequestProcessor</code> subclass.
*
* <p>The default implementation delegates to the {@link DelegatingActionUtils}
* class as much as possible, to reuse as much code as possible with
* <code>DelegatingRequestProcessor</code> and
* {@link DelegatingTilesRequestProcessor}.
*
* <p>Note: The idea of delegating to Spring-managed Struts Actions originated in
* Don Brown's <a href="http://struts.sourceforge.net/struts-spring">Spring Struts Plugin</a>.
* <code>ContextLoaderPlugIn</code> and <code>DelegatingActionProxy</code>
* 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
* Spring proper!
*
* @author Juergen Hoeller
* @since 1.0.1
* @see #determineActionBeanName
* @see DelegatingRequestProcessor
* @see DelegatingTilesRequestProcessor
* @see DelegatingActionUtils
* @see ContextLoaderPlugIn
*/
public class DelegatingActionProxy extends Action {
/**
* Pass the execute call on to the Spring-managed delegate <code>Action</code>.
* @see #getDelegateAction
*/
public ActionForward execute(
ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response)
throws Exception {
Action delegateAction = getDelegateAction(mapping);
return delegateAction.execute(mapping, form, request, response);
}
/**
* Return the delegate <code>Action</code> for the given <code>mapping</code>.
* <p>The default implementation determines a bean name from the
* given <code>ActionMapping</code> and looks up the corresponding bean in
* the {@link WebApplicationContext}.
* @param mapping the Struts <code>ActionMapping</code>
* @return the delegate <code>Action</code>
* @throws BeansException if thrown by <code>WebApplicationContext</code> methods
* @see #determineActionBeanName
*/
protected Action getDelegateAction(ActionMapping mapping) throws BeansException {
WebApplicationContext wac = getWebApplicationContext(getServlet(), mapping.getModuleConfig());
String beanName = determineActionBeanName(mapping);
return (Action) wac.getBean(beanName, Action.class);
}
/**
* Fetch ContextLoaderPlugIn's {@link WebApplicationContext} from the
* <code>ServletContext</code>, falling back to the root
* <code>WebApplicationContext</code>.
* <p>This context is supposed to contain the Struts <code>Action</code>
* beans to delegate to.
* @param actionServlet the associated <code>ActionServlet</code>
* @param moduleConfig the associated <code>ModuleConfig</code>
* @return the <code>WebApplicationContext</code>
* @throws IllegalStateException if no <code>WebApplicationContext</code> could be found
* @see DelegatingActionUtils#findRequiredWebApplicationContext
* @see ContextLoaderPlugIn#SERVLET_CONTEXT_PREFIX
*/
protected WebApplicationContext getWebApplicationContext(
ActionServlet actionServlet, ModuleConfig moduleConfig) throws IllegalStateException {
return DelegatingActionUtils.findRequiredWebApplicationContext(actionServlet, moduleConfig);
}
/**
* Determine the name of the <code>Action</code> bean, to be looked up in
* the <code>WebApplicationContext</code>.
* <p>The default implementation takes the
* {@link org.apache.struts.action.ActionMapping#getPath mapping path} and
* prepends the
* {@link org.apache.struts.config.ModuleConfig#getPrefix module prefix},
* if any.
* @param mapping the Struts <code>ActionMapping</code>
* @return the name of the Action bean
* @see DelegatingActionUtils#determineActionBeanName
* @see org.apache.struts.action.ActionMapping#getPath
* @see org.apache.struts.config.ModuleConfig#getPrefix
*/
protected String determineActionBeanName(ActionMapping mapping) {
return DelegatingActionUtils.determineActionBeanName(mapping);
}
}