RequestAttributes


1   /*
2    * Copyright 2002-2007 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  /**
20   * Abstraction for accessing attribute objects associated with a request.
21   * Supports access to request-scoped attributes as well as to session-scoped
22   * attributes, with the optional notion of a "global session".
23   *
24   * <p>Can be implemented for any kind of request/session mechanism,
25   * in particular for servlet requests and portlet requests.
26   *
27   * @author Juergen Hoeller
28   * @since 2.0
29   * @see ServletRequestAttributes
30   * @see org.springframework.web.portlet.context.PortletRequestAttributes
31   */
32  public interface RequestAttributes {
33  
34      /**
35       * Constant that indicates request scope.
36       */
37      int SCOPE_REQUEST = 0;
38  
39      /**
40       * Constant that indicates session scope.
41       * <p>This preferably refers to a locally isolated session, if such
42       * a distinction is available (for example, in a Portlet environment).
43       * Else, it simply refers to the common session.
44       */
45      int SCOPE_SESSION = 1;
46  
47      /**
48       * Constant that indicates global session scope.
49       * <p>This explicitly refers to a globally shared session, if such
50       * a distinction is available (for example, in a Portlet environment).
51       * Else, it simply refers to the common session.
52       */
53      int SCOPE_GLOBAL_SESSION = 2;
54  
55  
56      /**
57       * Return the value for the scoped attribute of the given name, if any.
58       * @param name the name of the attribute
59       * @param scope the scope identifier
60       * @return the current attribute value, or <code>null</code> if not found
61       */
62      Object   getAttribute(String   name, int scope);
63  
64      /**
65       * Set the value for the scoped attribute of the given name,
66       * replacing an existing value (if any).
67       * @param name the name of the attribute
68       * @param scope the scope identifier
69       * @param value the value for the attribute
70       */
71      void setAttribute(String   name, Object   value, int scope);
72  
73      /**
74       * Remove the scoped attribute of the given name, if it exists.
75       * <p>Note that an implementation should also remove a registered destruction
76       * callback for the specified attribute, if any. It does, however, <i>not</i>
77       * need to <i>execute</i> a registered destruction callback in this case,
78       * since the object will be destroyed by the caller (if appropriate).
79       * @param name the name of the attribute
80       * @param scope the scope identifier
81       */
82      void removeAttribute(String   name, int scope);
83  
84      /**
85       * Register a callback to be executed on destruction of the
86       * specified attribute in the given scope.
87       * <p>Implementations should do their best to execute the callback
88       * at the appropriate time: that is, at request completion or session
89       * termination, respectively. If such a callback is not supported by the
90       * underlying runtime environment, the callback <i>must be ignored</i>
91       * and a corresponding warning should be logged.
92       * <p>Note that 'destruction' usually corresponds to destruction of the
93       * entire scope, not to the individual attribute having been explicitly
94       * removed by the application. If an attribute gets removed via this
95       * facade's {@link #removeAttribute(String, int)} method, any registered
96       * destruction callback should be disabled as well, assuming that the
97       * removed object will be reused or manually destroyed.
98       * @param name the name of the attribute to register the callback for
99       * @param callback the destruction callback to be executed
100      * @param scope the scope identifier
101      */
102     void registerDestructionCallback(String   name, Runnable   callback, int scope);
103 
104     /**
105      * Return an id for the current underlying session.
106      * @return the session id as String (never <code>null</code>
107      */
108     String   getSessionId();
109 
110     /**
111      * Expose the best available mutex for the underlying session:
112      * that is, an object to synchronize on for the underlying session.
113      * @return the session mutex to use (never <code>null</code>
114      */
115     Object   getSessionMutex();
116 
117 }
118
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