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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package javax.faces.application;
20  
21  
22  import org.apache.myfaces.buildtools.maven2.plugin.builder.annotation.JSFWebConfigParam;
23  
24  import java.io.IOException;
25  
26  import javax.faces.component.UIViewRoot;
27  import javax.faces.context.FacesContext;
28  
29  /**
30   * Responsible for storing sufficient information about a component tree so that an identical tree can later be
31   * recreated.
32   * <p>
33   * It is up to the concrete implementation to decide whether to use information from the "view template" that was used
34   * to first create the view, or whether to store sufficient information to enable the view to be restored without any
35   * reference to the original template. However as JSF components have mutable fields that can be set by code, and
36   * affected by user input, at least some state does need to be kept in order to recreate a previously-existing component
37   * tree.
38   * <p>
39   * There are two different options defined by the specification: "client" and "server" state.
40   * <p>
41   * When "client" state is configured, all state information required to create the tree is embedded within the data
42   * rendered to the client. Note that because data received from a remote client must always be treated as "tainted",
43   * care must be taken when using such data. Some StateManager implementations may use encryption to ensure that clients
44   * cannot modify the data, and that the data received on postback is therefore trustworthy.
45   * <p>
46   * When "server" state is configured, the data is saved somewhere "on the back end", and (at most) a token is embedded
47   * in the data rendered to the user.
48   * <p>
49   * This class is usually invoked by a concrete implementation of ViewHandler.
50   * <p>
51   * Note that class ViewHandler isolates JSF components from the details of the request format. This class isolates JSF
52   * components from the details of the response format. Because request and response are usually tightly coupled, the
53   * StateManager and ViewHandler implementations are also usually fairly tightly coupled (ie the ViewHandler/StateManager
54   * implementations come as pairs).
55   * <p>
56   * See also the <a href="http://java.sun.com/javaee/javaserverfaces/1.2/docs/api/index.html">JSF Specification</a>
57   * 
58   * @author Manfred Geiler (latest modification by $Author: bommel $)
59   * @author Stan Silvert
60   * @version $Revision: 1187700 $ $Date: 2011-10-22 12:19:37 +0000 (Sat, 22 Oct 2011) $
61   */
62  public abstract class StateManager
63  {
64      /**
65       * Define the state method to be used. There are two different options defined by the 
66       * specification: "client" and "server" state.
67       * <p>
68       * When "client" state is configured, all state information required to create the tree is embedded within
69       * the data rendered to the client. Note that because data received from a remote client must always be
70       * treated as "tainted", care must be taken when using such data. Some StateManager implementations may
71       * use encryption to ensure that clients cannot modify the data, and that the data received on postback
72       * is therefore trustworthy.
73       * </p>
74       * <p>
75       * When "server" state is configured, the data is saved somewhere "on the back end", and (at most) a
76       * token is embedded in the data rendered to the user.
77       * </p>
78       */
79      @JSFWebConfigParam(defaultValue="server", expectedValues="server,client", since="1.1", group="state", tags="performance",
80          desc="Define the state method to be used. There are two different options defined by the specification: 'client' and 'server' state.")
81      public static final String STATE_SAVING_METHOD_PARAM_NAME = "javax.faces.STATE_SAVING_METHOD";
82      public static final String STATE_SAVING_METHOD_CLIENT = "client";
83      public static final String STATE_SAVING_METHOD_SERVER = "server";
84      
85      /**
86       * Indicate the viewId(s) separated by commas that should be saved and restored fully, without use Partial State Saving (PSS). 
87       */
88      @JSFWebConfigParam(since="2.0", group="state")
89      public static final String FULL_STATE_SAVING_VIEW_IDS_PARAM_NAME = "javax.faces.FULL_STATE_SAVING_VIEW_IDS";
90      
91      /**
92       * Enable or disable partial state saving algorithm.
93       *  
94       * <p>Partial State Saving algorithm allows to reduce the size of the state required to save a view, 
95       * keeping track of the "delta" or differences between the view build by first time and the current 
96       * state of the view.</p>
97       * <p>If the webapp faces-config file version is 2.0 or upper the default value is true, otherwise is false.</p>   
98       */
99      @JSFWebConfigParam(expectedValues="true,false", since="2.0", defaultValue="true (false with 1.2 webapps)", tags="performance", group="state")
100     public static final String PARTIAL_STATE_SAVING_PARAM_NAME = "javax.faces.PARTIAL_STATE_SAVING";
101     private Boolean _savingStateInClient = null;
102 
103     /**
104      * Invokes getTreeStructureToSave and getComponentStateToSave, then return an object that wraps the two resulting
105      * objects. This object can then be passed to method writeState.
106      * <p>
107      * Deprecated; use saveView instead.
108      * 
109      * @deprecated
110      */
111     public StateManager.SerializedView saveSerializedView(FacesContext context)
112     {
113         Object savedView = saveView(context);
114         if (savedView != null && savedView instanceof Object[])
115         {
116             Object[] structureAndState = (Object[]) savedView;
117             if (structureAndState.length == 2)
118             {
119                 return new StateManager.SerializedView(structureAndState[0], structureAndState[1]);
120             }
121         }
122         
123         return null;
124     }
125 
126     /**
127      * Returns an object that is sufficient to recreate the component tree that is the viewroot of the specified
128      * context.
129      * <p>
130      * The return value is suitable for passing to method writeState.
131      * 
132      * @since 1.2
133      */
134     public Object saveView(FacesContext context)
135     {
136         StateManager.SerializedView serializedView = saveSerializedView(context);
137         if (serializedView == null)
138             return null;
139 
140         Object[] structureAndState = new Object[2];
141         structureAndState[0] = serializedView.getStructure();
142         structureAndState[1] = serializedView.getState();
143 
144         return structureAndState;
145     }
146 
147     /**
148      * Return data that is sufficient to recreate the component tree that is the viewroot of the specified context, but
149      * without restoring the state in the components.
150      * <p>
151      * Using this data, a tree of components which has the same "shape" as the original component tree can be recreated.
152      * However the component instances themselves will have only their default values, ie their member fields will not
153      * have been set to the original values.
154      * <p>
155      * Deprecated; use saveView instead.
156      * 
157      * @deprecated
158      */
159     protected Object getTreeStructureToSave(FacesContext context)
160     {
161         return null;
162     }
163 
164     /**
165      * Return data that can be applied to a component tree created using the "getTreeStructureToSave" method.
166      * <p>
167      * Deprecated; use saveView instead.
168      * 
169      * @deprecated
170      */
171     protected Object getComponentStateToSave(FacesContext context)
172     {
173         return null;
174     }
175 
176     /**
177      * Associate the provided state object with the current response being generated.
178      * <p>
179      * When client-side state is enabled, it is expected that method writes the data contained in the state parameter to
180      * the response somehow.
181      * <p>
182      * When server-side state is enabled, at most a "token" is expected to be written.
183      * <p>
184      * Deprecated; use writeState(FacesContext, Object) instead. This method was abstract in JSF1.1, but is now an empty
185      * non-abstract method so that old classes that implement this method continue to work, while new classes can just
186      * override the new writeState method rather than this one.
187      * 
188      * @throws IOException
189      *             never
190      * 
191      * @deprecated
192      */
193     public void writeState(FacesContext context, StateManager.SerializedView state)
194         throws IOException
195     {
196         if (state != null)
197         {
198             writeState(context, new Object[]{state.getStructure(), state.getState()});
199         }
200     }
201 
202     /**
203      * Associate the provided state object with the current response being generated.
204      * <p>
205      * When client-side state is enabled, it is expected that method writes the data contained in the state parameter to
206      * the response somehow.
207      * <p>
208      * When server-side state is enabled, at most a "token" is expected to be written.
209      * <p>
210      * This method should be overridden by subclasses. It is not abstract because a default implementation is provided
211      * that forwards to the old writeState method; this allows subclasses of StateManager written using the JSF1.1 API
212      * to continue to work.
213      * <p>
214      * 
215      * @since 1.2
216      */
217     public void writeState(FacesContext context, Object state) throws IOException
218     {
219         if (!(state instanceof Object[]))
220             return;
221         Object[] structureAndState = (Object[]) state;
222         if (structureAndState.length < 2)
223             return;
224 
225         writeState(context, new StateManager.SerializedView(structureAndState[0], structureAndState[1]));
226     }
227     
228     /**
229      * TODO: This method should be called from somewhere when ajax response is created to update the state saving param
230      * on client. The place where this method is called is an implementation detail, so there is no references about
231      * from where in the spec javadoc. 
232      * 
233      * @since 2.0
234      * @param context
235      * @return
236      */
237     public String getViewState(FacesContext context)
238     {
239         return context.getRenderKit().getResponseStateManager().getViewState(context, saveView(context));
240     }
241 
242     public abstract UIViewRoot restoreView(FacesContext context, String viewId, String renderKitId);
243 
244     /**
245      * @deprecated
246      */
247     protected UIViewRoot restoreTreeStructure(FacesContext context, String viewId, String renderKitId)
248     {
249         return null;
250     }
251 
252     /**
253      * @deprecated
254      */
255     protected void restoreComponentState(FacesContext context, UIViewRoot viewRoot, String renderKitId)
256     {
257         // default impl does nothing as per JSF 1.2 javadoc
258     }
259 
260     public boolean isSavingStateInClient(FacesContext context)
261     {
262         if (context == null)
263             throw new NullPointerException("context");
264         if (_savingStateInClient != null)
265             return _savingStateInClient.booleanValue();
266         String stateSavingMethod = context.getExternalContext().getInitParameter(STATE_SAVING_METHOD_PARAM_NAME);
267         if (stateSavingMethod == null)
268         {
269             _savingStateInClient = Boolean.FALSE; // Specs 10.1.3: default server saving
270             context.getExternalContext().log("No state saving method defined, assuming default server state saving");
271         }
272         else if (stateSavingMethod.equals(STATE_SAVING_METHOD_CLIENT))
273         {
274             _savingStateInClient = Boolean.TRUE;
275         }
276         else if (stateSavingMethod.equals(STATE_SAVING_METHOD_SERVER))
277         {
278             _savingStateInClient = Boolean.FALSE;
279         }
280         else
281         {
282             _savingStateInClient = Boolean.FALSE; // Specs 10.1.3: default server saving
283             context.getExternalContext().log(
284                 "Illegal state saving method '" + stateSavingMethod + "', default server state saving will be used");
285         }
286         return _savingStateInClient.booleanValue();
287     }
288 
289     /**
290      * @deprecated
291      */
292     public class SerializedView
293     {
294         private Object _structure;
295         private Object _state;
296 
297         /**
298          * @deprecated
299          */
300         public SerializedView(Object structure, Object state)
301         {
302             _structure = structure;
303             _state = state;
304         }
305 
306         /**
307          * @deprecated
308          */
309         public Object getStructure()
310         {
311             return _structure;
312         }
313 
314         /**
315          * @deprecated
316          */
317         public Object getState()
318         {
319             return _state;
320         }
321     }
322 }