craigmcc 2003/02/04 20:23:20
Modified: doc/faqs newbie.xml
Log:
Add the "how to prepopulate a form bean" answer, illustrated with how its
done in the struts-example webapp.
PR: Bugzilla #16066
Submitted by: Edgar Dollin <edgar at blue-moose.net>
Revision Changes Path
1.12 +82 -2 jakarta-struts/doc/faqs/newbie.xml
Index: newbie.xml
===================================================================
RCS file: /home/cvs/jakarta-struts/doc/faqs/newbie.xml,v
retrieving revision 1.11
retrieving revision 1.12
diff -u -r1.11 -r1.12
--- newbie.xml 5 Feb 2003 04:03:14 -0000 1.11
+++ newbie.xml 5 Feb 2003 04:23:20 -0000 1.12
@@ -106,6 +106,10 @@
for every HTML form?</a>
</li>
+ <li>
+ <a href="#prepopulate">How can I prepopulate a form?</a>
+ </li>
+
</ul>
<p>
@@ -619,6 +623,84 @@
</section>
+<section href="prepopulate"
+ name="How can I prepopulate a form?">
+
+ <p>The simplest way to preopulate a form is to have an <code>Action</code>
+ whose sole purpose is to populate an <code>ActionForm</code> and forward
+ to the servoet or JSP to render that form back to the client. A separate
+ <code>Action</code> would then be use to process the submitted form fields,
+ by declaring an instance of the same form bean name.</p>
+
+ <p>The <em>struts-example</em> example application that is shipped
+ with Struts illustrates this design pattern nicely. Note the following
+ definitions from the <code>struts-config.xml</code> file:</p>
+ <pre>
+ ...
+ <form-beans>
+ ...
+ <-- Registration form bean -->
+ <form-bean name="registrationForm"
+ type="org.apache.struts.webapp.example.RegistrationForm"/>
+ ...
+ </form-beans>
+ ...
+ <action-mappings>
+ ...
+ <-- Edit user registration -->
+ <action path="/editRegistration"
+ type="org.apache.struts.webapp.example.EditRegistrationAction"
+ name="registrationForm"
+ scope="request"
+ validate="false"/>
+ ...
+ <-- Save user registration -->
+ <action path="/saveRegistration"
+ type="org.apache.struts.webapp.example.SaveRegistrationAction"
+ name="registrationForm"
+ input="registration"
+ scope="request"/>
+ ...
+ </action-mappings>
+ </pre>
+
+ <p>Note the following features of this approach:</p>
+ <ul>
+ <li>Both the <code>/editRegistration</code> and
+ <code>/saveRegistration</code> actions use the same form bean.</li>
+ <li>When the <code>/editRegistration</code> action is entered, Struts
+ will have pre-created an empty form bean instance, and passed it to
+ the <code>execute()</code> method. The setup action is free to
+ preconfigure the values that will be displayed when the form is
+ rendered, simply by setting the corresponding form bean properties.
+ </li>
+ <li>When the setup action completes configuring the properties of the
+ form bean, it should return an <code>ActionForm</code> that points
+ at the page which will display this form. If you are using the
+ Struts JSP tag library, the <code>action</code> attribute on your
+ <html:form> tag will be set to <code>/saveRegistration</code>
+ in order for the form to be submitted to the processing action.</li>
+ <li>Note that the setup action (<code>/editRegistration</code>) turns off
+ validation on the form that is being set up. You will normally want
+ to include this attribute in the configuration of your setup actions,
+ because you are not planning to actually process the results -- you
+ simply want to take advantage of the fact that Struts will precreate
+ a form bean instance of the correct class for you.</li>
+ <li>The processing action (<code>/saveRegistration</code>), on the other
+ hand, leaves out the <code>validate</code> attribute, which defaults
+ to <code>true</code>. This tells Struts to perform the validations
+ associated with this form bean before invoking the processing action
+ at all. If any validation errors have occurred, Struts will forward
+ back to your input page (technically, it forwards back to an
+ <code>ActionForward</code> named "registration" in this case, because
+ the example webapp uses the <code>inputForward</code> attribute in the
+ <code><controller></code> element -- see the documentation
+ describing <code>struts-config.xml</code> for more information)
+ instead of calling your processing action.</li>
+ </ul>
+
+</section>
+
<section
href="undocumented"
@@ -630,8 +712,6 @@
<li>Why is ActionForm a base class rather than an interface?</li>
<li>Can I use other beans or hashmaps with ActionForms?</li>
-
- <li>How can I prepopulate a form?</li>
<li>How can I capture binary or formatted values, like dates or telephone
numbers?</li>
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