husted 02/02/23 17:13:13 Modified: doc newbie.xml Log: Add answer for checkbox question. Revision Changes Path 1.2 +27 -2 jakarta-struts/doc/newbie.xml Index: newbie.xml =================================================================== RCS file: /home/cvs/jakarta-struts/doc/newbie.xml,v retrieving revision 1.1 retrieving revision 1.2 diff -u -r1.1 -r1.2 --- newbie.xml 20 Feb 2002 00:42:49 -0000 1.1 +++ newbie.xml 24 Feb 2002 01:13:13 -0000 1.2 @@ -11,12 +11,12 @@ <p>Here are answers to twenty common questions people ask when using Struts on their first project. <b>For an in-depth, searchable FAQ, visit our friends at <a href="http://www.jguru.com/faq/home.jsp?topic=Struts";>JGuru</a>.</b></p> <ul> - <li><a href="#actionforms">Why is ActionForm a base class rather than an interface?</a></li> + <li>Why is ActionForm a base class rather than an interface?</li> <li>Do I have to have a separate ActionForm bean for every HTML form?</li> <li>Can I use other beans or hashmaps with ActionForms?</li> <li>How can I prepopulate a form?</li> <li>Can I use multiple HTML form elements with the same name?</li> - <li>Why are my checkboxes not being set from ON to OFF?</li> + <li><a href="#actionforms">hy are my checkboxes not being set from ON to OFF?</a></li> <li>How can I capture binary or formatted values, like dates or telephone numbers?</li> <li>Why do my option lists disappear when validation fails?</li> <li>Can't I just create some of my JavaBeans on the JSP using a scriptlet?</li> @@ -40,7 +40,32 @@ http://www.mail-archive.com/struts-user@jakarta.apache.org/msg19338.html<br/> http://www.mail-archive.com/struts-user@jakarta.apache.org/msg20833.html<br/> </p> +</section> +<section href="checkbox" name="Why are my checkboxes not being set from ON to OFF?"> +<p> +A problem with a checkbox is that the browser will only include it in the request +when it is checked. If it is not checked, the HTML specification suggests that it +not be sent (i.e. omitted from the request). If the value of the checkbox is being +persisted, either in a session bean or in the model, a checked box can never +unchecked by a HTML form -- because the form can never send a signal to uncheck +the box. The application must somehow ascertain that since the element was not +sent that the corresponding value is unchecked. +</p> +<p> +The recommended approach for Struts applications is to use the reset method in the +ActionForm to set all properties represented by checkboxes to null or false. The +checked boxes submitted by the form will then set those properties to true. The +omitted properties will remain false. Another solution is to use radio buttons +instead, which always submit a value. +</p> +<p> +It is important to note that the HTML specification recommends this same +behavior whenever a control is not "successful". Any blank element in a HTML +form is not guaranteed to submitted. It is therefor very important to set the +default values for an ActionForm correctly, and to implement the reset method +when the ActionForm might kept in session scope. +</p> </section> </chapter></body></document>
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