ServletForwardingController


1   /*
2    * Copyright 2002-2006 the original author or authors.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.web.servlet.mvc;
18  
19  import javax.servlet.RequestDispatcher  ;
20  import javax.servlet.ServletException  ;
21  import javax.servlet.http.HttpServletRequest  ;
22  import javax.servlet.http.HttpServletResponse  ;
23  
24  import org.springframework.beans.factory.BeanNameAware;
25  import org.springframework.web.servlet.ModelAndView;
26  import org.springframework.web.util.WebUtils;
27  
28  /**
29   * Spring Controller implementation that forwards to a named servlet,
30   * i.e. the "servlet-name" in web.xml rather than a URL path mapping.
31   * A target servlet doesn't even need a "servlet-mapping" in web.xml
32   * in the first place: A "servlet" declaration is sufficient.
33   *
34   * <p>Useful to invoke an existing servlet via Spring's dispatching infrastructure,
35   * for example to apply Spring HandlerInterceptors to its requests. This will work
36   * even in a Servlet 2.2 container that does not support Servlet filters.
37   *
38   * <p>In particular, the main intent of this controller is to allow for applying
39   * Spring's OpenSessionInViewInterceptor or OpenPersistenceManagerInViewInterceptor
40   * to servlets in a Servlet 2.2 container. The specified "servlet-name" will
41   * simply refer to a custom servlet definition in web.xml in such a scenario.
42   * You then need to map "/myservlet" (or whatever path you choose for your servlet)
43   * onto this controller, which will in turn forward to your servlet.
44   *
45   * <p>In a Servlet 2.3 container, when not using Spring's own web MVC framework,
46   * it is recommended to use classic servlet mapping in combination with a filter,
47   * for example Spring's OpenSessionInViewFilter or OpenPersistenceManagerInViewFilter.
48   *
49   * <p><b>Example:</b> web.xml, mapping all "/myservlet" requests to a Spring dispatcher.
50   * Also defines a custom "myServlet", but <i>without</i> servlet mapping.
51   *
52   * <pre>
53   * &lt;servlet&gt;
54   *   &lt;servlet-name&gt;myServlet&lt;/servlet-name&gt;
55   *   &lt;servlet-class&gt;mypackage.TestServlet&lt;/servlet-class&gt;
56   * &lt;/servlet&gt;
57   *
58   * &lt;servlet&gt;
59   *   &lt;servlet-name&gt;myDispatcher&lt;/servlet-name&gt;
60   *   &lt;servlet-class&gt;org.springframework.web.servlet.DispatcherServlet&lt;/servlet-class&gt;
61   * &lt;/servlet&gt;
62   *
63   * &lt;servlet-mapping&gt;
64   *   &lt;servlet-name&gt;myDispatcher&lt;/servlet-name&gt;
65   *   &lt;url-pattern&gt;/myservlet&lt;/url-pattern&gt;
66   * &lt;/servlet-mapping&gt;</pre>
67   *
68   * <b>Example:</b> myDispatcher-servlet.xml, in turn forwarding "/myservlet" to your
69   * servlet (identified by servlet name). All such requests will go through the
70   * configured HandlerInterceptor chain (e.g. an OpenSessionInViewInterceptor).
71   * From the servlet point of view, everything will work as usual.
72   *
73   * <pre>
74   * &lt;bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping"&gt;
75   *   &lt;property name="interceptors"&gt;
76   *     &lt;list&gt;
77   *       &lt;ref bean="openSessionInViewInterceptor"/&gt;
78   *     &lt;/list&gt;
79   *   &lt;/property&gt;
80   *   &lt;property name="mappings"&gt;
81   *     &lt;props&gt;
82   *       &lt;prop key="/myservlet"&gt;myServletForwardingController&lt;/prop&gt;
83   *     &lt;/props&gt;
84   *   &lt;/property&gt;
85   * &lt;/bean&gt;
86   *
87   * &lt;bean id="myServletForwardingController" class="org.springframework.web.servlet.mvc.ServletForwardingController"&gt;
88   *   &lt;property name="servletName"&gt;&lt;value&gt;myServlet&lt;/value&gt;&lt;/property&gt;
89   * &lt;/bean&gt;</pre>
90   *
91   * @author Juergen Hoeller
92   * @since 1.1.1
93   * @see ServletWrappingController
94   * @see org.springframework.orm.hibernate.support.OpenSessionInViewInterceptor
95   * @see org.springframework.orm.hibernate.support.OpenSessionInViewFilter
96   * @see org.springframework.orm.jdo.support.OpenPersistenceManagerInViewInterceptor
97   * @see org.springframework.orm.jdo.support.OpenPersistenceManagerInViewFilter
98   */
99  public class ServletForwardingController extends AbstractController implements BeanNameAware {
100 
101     private String   servletName;
102 
103     private String   beanName;
104     
105 
106     /**
107      * Set the name of the servlet to forward to,
108      * i.e. the "servlet-name" of the target servlet in web.xml.
109      * <p>Default is the bean name of this controller.
110      */
111     public void setServletName(String   servletName) {
112         this.servletName = servletName;
113     }
114 
115     public void setBeanName(String   name) {
116         this.beanName = name;
117         if (this.servletName == null) {
118             this.servletName = name;
119         }
120     }
121 
122 
123     protected ModelAndView handleRequestInternal(HttpServletRequest   request, HttpServletResponse   response)
124             throws Exception   {
125 
126         RequestDispatcher   rd = getServletContext().getNamedDispatcher(this.servletName);
127         if (rd == null) {
128             throw new ServletException  ("No servlet with name '" + this.servletName + "' defined in web.xml");
129         }
130         // If already included, include again, else forward.
131         if (useInclude(request, response)) {
132             rd.include(request, response);
133             if (logger.isDebugEnabled()) {
134                 logger.debug("Included servlet [" + this.servletName +
135                         "] in ServletForwardingController '" + this.beanName + "'");
136             }
137         }
138         else {
139             rd.forward(request, response);
140             if (logger.isDebugEnabled()) {
141                 logger.debug("Forwarded to servlet [" + this.servletName +
142                         "] in ServletForwardingController '" + this.beanName + "'");
143             }
144         }
145         return null;
146     }
147 
148     /**
149      * Determine whether to use RequestDispatcher's <code>include</code> or
150      * <code>forward</code> method.
151      * <p>Performs a check whether an include URI attribute is found in the request,
152      * indicating an include request, and whether the response has already been committed.
153      * In both cases, an include will be performed, as a forward is not possible anymore.
154      * @param request current HTTP request
155      * @param response current HTTP response
156      * @return <code>true</code> for include, <code>false</code> for forward
157      * @see javax.servlet.RequestDispatcher#forward
158      * @see javax.servlet.RequestDispatcher#include
159      * @see javax.servlet.ServletResponse#isCommitted
160      * @see org.springframework.web.util.WebUtils#isIncludeRequest
161      */
162     protected boolean useInclude(HttpServletRequest   request, HttpServletResponse   response) {
163         return (WebUtils.isIncludeRequest(request) || response.isCommitted());
164     }
165 
166 }
167
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