/*
* 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.servlet.mvc;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.support.WebContentGenerator;
import org.springframework.web.util.WebUtils;
/**
* <p>Convenient superclass for controller implementations, using the Template
* Method design pattern.</p>
*
* <p>As stated in the {@link org.springframework.web.servlet.mvc.Controller Controller}
* interface, a lot of functionality is already provided by certain abstract
* base controllers. The AbstractController is one of the most important
* abstract base controller providing basic features such as the generation
* of caching headers and the enabling or disabling of
* supported methods (GET/POST).</p>
*
* <p><b><a name="workflow">Workflow
* (<a href="Controller.html#workflow">and that defined by interface</a>):</b><br>
* <ol>
* <li>{@link #handleRequest(HttpServletRequest,HttpServletResponse) handleRequest()}
* will be called by the DispatcherServlet</li>
* <li>Inspection of supported methods (ServletException if request method
* is not support)</li>
* <li>If session is required, try to get it (ServletException if not found)</li>
* <li>Set caching headers if needed according to the cacheSeconds property</li>
* <li>Call abstract method {@link #handleRequestInternal(HttpServletRequest,HttpServletResponse) handleRequestInternal()}
* (optionally synchronizing around the call on the HttpSession),
* which should be implemented by extending classes to provide actual
* functionality to return {@link org.springframework.web.servlet.ModelAndView ModelAndView} objects.</li>
* </ol>
* </p>
*
* <p><b><a name="config">Exposed configuration properties</a>
* (<a href="Controller.html#config">and those defined by interface</a>):</b><br>
* <table border="1">
* <tr>
* <td><b>name</b></th>
* <td><b>default</b></td>
* <td><b>description</b></td>
* </tr>
* <tr>
* <td>supportedMethods</td>
* <td>GET,POST</td>
* <td>comma-separated (CSV) list of methods supported by this controller,
* such as GET, POST and PUT</td>
* </tr>
* <tr>
* <td>requireSession</td>
* <td>false</td>
* <td>whether a session should be required for requests to be able to
* be handled by this controller. This ensures that derived controller
* can - without fear of null pointers - call request.getSession() to
* retrieve a session. If no session can be found while processing
* the request, a ServletException will be thrown</td>
* </tr>
* <tr>
* <td>cacheSeconds</td>
* <td>-1</td>
* <td>indicates the amount of seconds to include in the cache header
* for the response following on this request. 0 (zero) will include
* headers for no caching at all, -1 (the default) will not generate
* <i>any headers</i> and any positive number will generate headers
* that state the amount indicated as seconds to cache the content</td>
* </tr>
* <tr>
* <td>synchronizeOnSession</td>
* <td>false</td>
* <td>whether the call to <code>handleRequestInternal</code> should be
* synchronized around the HttpSession, to serialize invocations
* from the same client. No effect if there is no HttpSession.
* </td>
* </tr>
* </table>
*
* @author Rod Johnson
* @author Juergen Hoeller
* @see WebContentInterceptor
*/
public abstract class AbstractController extends WebContentGenerator implements Controller {
private boolean synchronizeOnSession = false;
/**
* Set if controller execution should be synchronized on the session,
* to serialize parallel invocations from the same client.
* <p>More specifically, the execution of the <code>handleRequestInternal</code>
* method will get synchronized if this flag is "true". The best available
* session mutex will be used for the synchronization; ideally, this will
* be a mutex exposed by HttpSessionMutexListener.
* <p>The session mutex is guaranteed to be the same object during
* the entire lifetime of the session, available under the key defined
* by the <code>SESSION_MUTEX_ATTRIBUTE</code> constant. It serves as a
* safe reference to synchronize on for locking on the current session.
* <p>In many cases, the HttpSession reference itself is a safe mutex
* as well, since it will always be the same object reference for the
* same active logical session. However, this is not guaranteed across
* different servlet containers; the only 100% safe way is a session mutex.
* @see org.springframework.web.servlet.mvc.AbstractController#handleRequestInternal
* @see org.springframework.web.util.HttpSessionMutexListener
* @see org.springframework.web.util.WebUtils#getSessionMutex(javax.servlet.http.HttpSession)
*/
public final void setSynchronizeOnSession(boolean synchronizeOnSession) {
this.synchronizeOnSession = synchronizeOnSession;
}
/**
* Return whether controller execution should be synchronized on the session.
*/
public final boolean isSynchronizeOnSession() {
return this.synchronizeOnSession;
}
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response)
throws Exception {
// Delegate to WebContentGenerator for checking and preparing.
checkAndPrepare(request, response, this instanceof LastModified);
// Execute handleRequestInternal in synchronized block if required.
if (this.synchronizeOnSession) {
HttpSession session = request.getSession(false);
if (session != null) {
Object mutex = WebUtils.getSessionMutex(session);
synchronized (mutex) {
return handleRequestInternal(request, response);
}
}
}
return handleRequestInternal(request, response);
}
/**
* Template method. Subclasses must implement this.
* The contract is the same as for <code>handleRequest</code>.
* @see #handleRequest
*/
protected abstract ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response)
throws Exception;
}
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