/*
* 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 java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionServlet;
import org.apache.struts.action.RequestProcessor;
import org.apache.struts.config.ModuleConfig;
import org.springframework.beans.BeansException;
import org.springframework.web.context.WebApplicationContext;
/**
* Subclass of Struts's default {@link RequestProcessor} that looks up
* Spring-managed Struts {@link Action Actions} defined in
* {@link ContextLoaderPlugIn ContextLoaderPlugIn's} {@link WebApplicationContext}
* (or, as a fallback, in the root <code>WebApplicationContext</code>).
*
* <p>In the Struts config file, you can either specify the original
* <code>Action</code> class (as when generated by XDoclet), or no
* <code>Action</code> class at all. In any case, Struts will delegate to an
* <code>Action</code> bean in the <code>ContextLoaderPlugIn</code> context.
*
* <pre class="code"><action path="/login" type="myapp.MyAction"/></pre>
*
* or
*
* <pre class="code"><action path="/login"/></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
* {@link #determineActionBeanName} 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 also need the Tiles setup functionality of the original
* <code>TilesRequestProcessor</code>, use
* <code>DelegatingTilesRequestProcessor</code>. As there is just a
* single central class to customize in Struts, we have to provide another
* subclass here, covering both the Tiles and the Spring delegation aspect.
*
* <p>If this <code>RequestProcessor</code> conflicts with the need for a
* different <code>RequestProcessor</code> subclass (other than
* <code>TilesRequestProcessor</code>), consider using
* {@link DelegatingActionProxy} as the Struts <code>Action</code> type in
* your struts-config file.
*
* <p>The default implementation delegates to the
* <code>DelegatingActionUtils</code> class as much as possible, to reuse as
* much code as possible despite the need to provide two
* <code>RequestProcessor</code> subclasses. If you need to subclass yet
* another <code>RequestProcessor</code>, take this class as a template,
* delegating to <code>DelegatingActionUtils</code> just like it.
*
* @author Juergen Hoeller
* @since 1.0.2
* @see #determineActionBeanName
* @see DelegatingTilesRequestProcessor
* @see DelegatingActionProxy
* @see DelegatingActionUtils
* @see ContextLoaderPlugIn
*/
public class DelegatingRequestProcessor extends RequestProcessor {
private WebApplicationContext webApplicationContext;
public void init(ActionServlet actionServlet, ModuleConfig moduleConfig) throws ServletException {
super.init(actionServlet, moduleConfig);
if (actionServlet != null) {
this.webApplicationContext = initWebApplicationContext(actionServlet, moduleConfig);
}
}
/**
* 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 initWebApplicationContext(
ActionServlet actionServlet, ModuleConfig moduleConfig) throws IllegalStateException {
return DelegatingActionUtils.findRequiredWebApplicationContext(actionServlet, moduleConfig);
}
/**
* Return the <code>WebApplicationContext</code> that this processor
* delegates to.
*/
protected final WebApplicationContext getWebApplicationContext() {
return this.webApplicationContext;
}
/**
* Override the base class method to return the delegate action.
* @see #getDelegateAction
*/
protected Action processActionCreate(
HttpServletRequest request, HttpServletResponse response, ActionMapping mapping)
throws IOException {
Action action = getDelegateAction(mapping);
if (action != null) {
return action;
}
return super.processActionCreate(request, response, mapping);
}
/**
* Return the delegate <code>Action</code> for the given mapping.
* <p>The default implementation determines a bean name from the
* given <code>ActionMapping</code> and looks up the corresponding
* bean in the <code>WebApplicationContext</code>.
* @param mapping the Struts <code>ActionMapping</code>
* @return the delegate <code>Action</code>, or <code>null</code> if none found
* @throws BeansException if thrown by <code>WebApplicationContext</code> methods
* @see #determineActionBeanName
*/
protected Action getDelegateAction(ActionMapping mapping) throws BeansException {
String beanName = determineActionBeanName(mapping);
if (!getWebApplicationContext().containsBean(beanName)) {
return null;
}
return (Action) getWebApplicationContext().getBean(beanName, Action.class);
}
/**
* 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);
}
}