?? clientstatetag.jsp
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<%-- Copyright 2002 Sun Microsystems, Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistribution in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. Neither the name of Sun Microsystems, Inc. or the names of contributors may be used to endorse or promote products derived from this software without specific prior written permission. This software is provided "AS IS," without a warranty of any kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. You acknowledge that Software is not designed, licensed or intended for use in the design, construction, operation or maintenance of any nuclear facility.--%><%@ taglib uri="/WEB-INF/waftags.tld" prefix="waf" %><html><font size="+3">Client State Tag</font><br/><br/>This page demonstrates the Client StateTag which will let youcache state witin a HTML page. Thus allowing for the user to return toa page with the same Request Parameters and HttpServletRequest Attributesand possibly more based on the actions that occured when the user left the page.<br/><br/>This tag works along with the ClientStateFlowHandler which is used tore-consititute the date that was saved on the client tier and return topage.<br/><br/><center><image src="images/clientstate.jpg"/></center>The graphic above describes how the client state tag may be used.For example an application needs to do some processing and return to thesame page with the same data. An example is when the user chooses tochange the language of the application. In which case the user will click onone of the flag images. The flag images are actually form submit buttons which contain forms that have data encoded in the form variables. Whenthe user clicks the image and action occurs in which the application localewhich the user prefers to view the pages in is changed. After the actionoccurs the user would like to be returned to the same page from whichthe button was pressed. This may have been during a search, whileviewing the shopping cart, or while viewing product data. In any one of thecases information about where the user is in the application is maintainedin data that is kept in request parameters and request attributes (requestscope data). In order to return to the place where the user was the informationabout where the user was must be stored.<br/><br/>The <b>client state tag</b> is responsible for creating the forms and the hidden form data which has the request attributes which are <b>serializable</b>encoded in Base64 format. A future version of this tag may use plugableserialize/de-serialize for serializing the data. This would allow a userto provide serializers/de-serializers that serialize/de-serialize data in encryptedformat. Currenlty it is not recommended to use this tag with confidential datain that it could be extracted from the page and de-serialized with a little work.<br/><br/>The <b>ClientStateFlowHandler</b> is responsible for de-serializing the datawhich and putting returning the user to the page/screen from which the actionoccured. The ClientStateFlowHandler is also responsible for forwarding theapplication to the screen from which the user departed.<br/><br/>This method of storing state on the client helps developers avoid problems thatare caused by clients navigating using the browers forward and back buttons. Thisis because the state is stored in the page itself and thus the user can return to theexact place in the application from which the user departed to preform an action.<br/><br/>This method of storing state allows an application to scale to a large number ofclients because the state is store on the clients. However this method of storestate requires the clients to be HTML clients and also does require bandwith inthat the state needs to be transferred along with each page request.<br/><br/>Click on the Submit Button to test the tag:<br/><br/><form action="clientstatetag_test.screen" method="POST"> <input type="HIDDEN" name="param1" value="apple"> <input type="HIDDEN" name="param2" value="orange"> <input type="HIDDEN" name="param3" value="pear"> <input type="SUBMIT" name="param1" value="Go to the Test Page"></form></html>?? 快捷鍵說明
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