WebRequestInterceptor


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.context.request;
18  
19  import org.springframework.ui.ModelMap;
20  
21  /**
22   * Interface for general web request interception. Allows for being applied
23   * to Servlet request as well as Portlet request environments, through
24   * building on the {@link WebRequest} abstraction.
25   *
26   * <p>This interface assumes MVC-style request processing: A handler gets executed,
27   * exposes a set of model objects, then a view gets rendered based on that model.
28   * Alternatively, a handler may also process the request completely, with no
29   * view to be rendered.
30   *
31   * <p>This interface is deliberatly minimalistic to keep the dependencies of
32   * generic request interceptors as minimal as feasible.
33   *
34   * <p><b>NOTE:</b> While this interceptor is applied to the entire request processing
35   * in a Servlet environment, it is by default only applied to the <i>render</i> phase
36   * in a Portlet environment, preparing and rendering a Portlet view. To apply
37   * WebRequestInterceptors to the <i>action</i> phase as well, set the HandlerMapping's
38   * "applyWebRequestInterceptorsToRenderPhaseOnly" flag to "false". Alternatively,
39   * consider using the Portlet-specific HandlerInterceptor mechanism for such needs.
40   *
41   * @author Juergen Hoeller
42   * @since 2.0
43   * @see ServletWebRequest
44   * @see org.springframework.web.servlet.DispatcherServlet
45   * @see org.springframework.web.servlet.handler.AbstractHandlerMapping#setInterceptors
46   * @see org.springframework.web.servlet.HandlerInterceptor
47   * @see org.springframework.web.portlet.context.PortletWebRequest
48   * @see org.springframework.web.portlet.DispatcherPortlet
49   * @see org.springframework.web.portlet.handler.AbstractHandlerMapping#setInterceptors
50   * @see org.springframework.web.portlet.handler.AbstractHandlerMapping#setApplyWebRequestInterceptorsToRenderPhaseOnly
51   * @see org.springframework.web.portlet.HandlerInterceptor
52   */
53  public interface WebRequestInterceptor {
54  
55      /**
56       * Intercept the execution of a request handler <i>before</i> its invocation.
57       * <p>Allows for preparing context resources (such as a Hibernate Session)
58       * and expose them as request attributes or as thread-local objects.
59       * @param request the current web request
60       * @throws Exception in case of errors
61       */
62      void preHandle(WebRequest request) throws Exception  ;
63  
64      /**
65       * Intercept the execution of a request handler <i>after</i> its successful
66       * invocation, right before view rendering (if any).
67       * <p>Allows for modifying context resources after successful handler
68       * execution (for example, flushing a Hibernate Session).
69       * @param request the current web request
70       * @param model the map of model objects that will be exposed to the view
71       * (may be <code>null</code>). Can be used to analyze the exposed model
72       * and/or to add further model attributes, if desired.
73       * @throws Exception in case of errors
74       */
75      void postHandle(WebRequest request, ModelMap model) throws Exception  ;
76  
77      /**
78       * Callback after completion of request processing, that is, after rendering
79       * the view. Will be called on any outcome of handler execution, thus allows
80       * for proper resource cleanup.
81       * <p>Note: Will only be called if this interceptor's <code>preHandle</code>
82       * method has successfully completed!
83       * @param request the current web request
84       * @param ex exception thrown on handler execution, if any
85       * @throws Exception in case of errors
86       */
87      void afterCompletion(WebRequest request, Exception   ex) throws Exception  ;
88  
89  }
90
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