Author: buildbot
Date: Sat Aug  1 21:19:50 2015
New Revision: 960452

Log:
Production update by buildbot for tapestry

Modified:
    websites/production/tapestry/content/cache/main.pageCache
    websites/production/tapestry/content/forms-and-validation.html

Modified: websites/production/tapestry/content/cache/main.pageCache
==============================================================================
Binary files - no diff available.

Modified: websites/production/tapestry/content/forms-and-validation.html
==============================================================================
--- websites/production/tapestry/content/forms-and-validation.html (original)
+++ websites/production/tapestry/content/forms-and-validation.html Sat Aug  1 
21:19:50 2015
@@ -67,7 +67,7 @@
   </div>
 
 <div id="content">
-<div id="ConfluenceContent"><p><strong>Form input and validation</strong> is 
the most effective way&#160;for most web applications to gather significant 
information from the user. Whether it's a search form, a login screen or a 
multi-page registration wizard, forms are how the user really expresses 
themselves to the application.</p><div class="aui-label" style="float:right" 
title="Related Articles">
+<div id="ConfluenceContent"><p><strong>Forms</strong> are the traditional way 
for most web applications to gather significant information from the user. 
Whether it's a search form, a login screen or a multi-page registration wizard, 
Tapestry uses standard HTML forms, with HTTP POST actions by default. In 
addition, AJAX-based form submission is supported using <a shape="rect" 
href="ajax-and-zones.html">Zones</a>.</p><div class="aui-label" 
style="float:right" title="Related Articles">
 
 
 
@@ -106,19 +106,24 @@
                         
                     </div>
     </li></ul>
-</div><p>Tapestry excels at creating forms and validating input. Input 
validation is declarative, meaning you simply tell Tapestry what validations to 
apply to a given field, and it takes care of it on the server and (once 
implemented) on the client as well.</p><p>Finally, Tapestry is able to not only 
present the errors back to the user, but to decorate the fields and the labels 
for the fields, marking them as containing errors (primarily, using CSS 
effects).</p><p><strong>Contents</strong></p><p><style 
type="text/css">/*<![CDATA[*/
-div.rbtoc1437945581375 {padding: 0px;}
-div.rbtoc1437945581375 ul {list-style: disc;margin-left: 0px;}
-div.rbtoc1437945581375 li {margin-left: 0px;padding-left: 0px;}
+</div><p>&#160;</p><p>Tapestry provides support for creating and rendering 
forms, populating their fields, and validating user input. For simple cases, 
input validation is declarative, meaning you simply tell Tapestry what 
validations to apply to a given field, and it takes care of it on the server 
and (optionally) on the client as well. In addition, you can provide event 
handler methods&#160;in your page or component classes to handle more complex 
validation scenarios.</p><p>Finally, Tapestry not only makes it easy to present 
errors messages to the user, but it can also automatically highlight form 
fields when validation fails.</p><p><strong>Contents</strong></p><p><style 
type="text/css">/*<![CDATA[*/
+div.rbtoc1438463978457 {padding: 0px;}
+div.rbtoc1438463978457 ul {list-style: disc;margin-left: 0px;}
+div.rbtoc1438463978457 li {margin-left: 0px;padding-left: 0px;}
 
-/*]]>*/</style></p><div class="toc-macro rbtoc1437945581375">
+/*]]>*/</style></p><div class="toc-macro rbtoc1438463978457">
 <ul class="toc-indentation"><li>Related Articles</li></ul>
 <ul><li><a shape="rect" href="#FormsandValidation-TheFormComponent">The Form 
Component</a>
-<ul class="toc-indentation"><li><a shape="rect" 
href="#FormsandValidation-FormEvents">Form Events</a></li><li><a shape="rect" 
href="#FormsandValidation-TrackingValidationErrors">Tracking Validation 
Errors</a></li><li><a shape="rect" 
href="#FormsandValidation-StoringDataBetweenRequests">Storing Data Between 
Requests</a></li><li><a shape="rect" 
href="#FormsandValidation-ConfiguringFieldsandLabels">Configuring Fields and 
Labels</a></li><li><a shape="rect" 
href="#FormsandValidation-CentralizingValidationwith@Validate">Centralizing 
Validation with @Validate</a></li><li><a shape="rect" 
href="#FormsandValidation-ServerSideValidation">Server Side 
Validation</a></li><li><a shape="rect" 
href="#FormsandValidation-CustomizingValidationMessages">Customizing Validation 
Messages</a>
+<ul class="toc-indentation"><li><a shape="rect" 
href="#FormsandValidation-FormEvents">Form Events</a></li><li><a shape="rect" 
href="#FormsandValidation-HandlingEvents">Handling Events</a></li><li><a 
shape="rect" href="#FormsandValidation-TrackingValidationErrors">Tracking 
Validation Errors</a></li><li><a shape="rect" 
href="#FormsandValidation-StoringDataBetweenRequests">Storing Data Between 
Requests</a></li><li><a shape="rect" 
href="#FormsandValidation-ConfiguringFieldsandLabels">Configuring Fields and 
Labels</a></li><li><a shape="rect" 
href="#FormsandValidation-CentralizingValidationwith@Validate">Centralizing 
Validation with @Validate</a></li><li><a shape="rect" 
href="#FormsandValidation-ServerSideValidation">Server Side 
Validation</a></li><li><a shape="rect" 
href="#FormsandValidation-CustomizingValidationMessages">Customizing Validation 
Messages</a>
 <ul class="toc-indentation"><li><a shape="rect" 
href="#FormsandValidation-CustomizingValidationMessagesforBeanEditForm">Customizing
 Validation Messages for BeanEditForm</a></li></ul>
 </li><li><a shape="rect" 
href="#FormsandValidation-ConfiguringValidatorContraintsintheMessageCatalog">Configuring
 Validator Contraints in the Message Catalog</a></li><li><a shape="rect" 
href="#FormsandValidation-ValidationMacros">Validation Macros</a></li><li><a 
shape="rect" 
href="#FormsandValidation-OverridingtheTranslatorwithEvents">Overriding the 
Translator with Events</a></li></ul>
-</li></ul></div><h1 id="FormsandValidation-TheFormComponent">The Form 
Component</h1><p>The core of Tapestry's form support is the <a shape="rect" 
class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/Form.html";>Form</a>
 component. The Form component encloses (wraps around) all the other <em>field 
components</em> such as <a shape="rect" class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/TextField.html";>TextField</a>,
 <a shape="rect" class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/TextArea.html";>TextArea</a>,
 <a shape="rect" class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/Checkbox.html";>Checkbox</a>,
 etc.</p><h2 id="FormsandValidation-FormEvents">Form Events</h2><p>The Form 
component emits a number of <a shape="rect" href="component-events.html">
 component events</a>. You'll need to provide event handler methods for some of 
these.</p><p>When rendering, the Form component emits two notifications: first, 
"prepareForRender", then "prepare". These allow the Form's container to setup 
any fields or properties that will be referenced in the form. For example, this 
is a good place to create a temporary entity object to be rendered, or to load 
an entity from a database to be edited.</p><p>When user submits the form on the 
client, a series of steps occur on the server.</p><p>First, the Form emits a 
"prepareForSubmit" notification, then a "prepare" notification. These allow the 
container to ensure that objects are set up and ready to receive information 
from the form submission.</p><p>Next, all the fields inside the form are 
activated to pull values out of the incoming request, validate them and (if 
valid) store the changes.</p><div class="navmenu" style="float:right; 
width:25%; background:#eee; margin:3px; padding:3px">
-<p><em>For Tapestry 4 Users:</em> Tapestry 5 does not use the fragile "form 
rewind" approach from Tapestry 4. Instead, a hidden field generated during the 
render stores the information needed to process the form 
submission.</p></div>After the fields have done their processing, the Form 
emits a "validate" event. This is a chance to perform cross-form validation 
that can't be described declaratively.<p>Note: For compatibility with release 
5.1 and earlier, the Form component also emits a "validateForm" event. (See <a 
shape="rect" class="external-link" 
href="https://issues.apache.org/jira/browse/TAP5-760";>TAP5-760</a>.)</p><p>Next,
 the Form determines if there have been any validation errors. If there have 
been, then the submission is considered a failure, and a "failure" event is 
emitted. If there have been no validation errors, then a "success" event is 
emitted.</p><p>Finally, the Form emits a "submit" event, for logic that doesn't 
care about success or failure.</p><div class="table-w
 rap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" 
class="confluenceTh"><p>Form Event (in order)</p></th><th colspan="1" 
rowspan="1" class="confluenceTh"><p>Phase</p></th><th colspan="1" rowspan="1" 
class="confluenceTh"><p>When emitted</p></th><th colspan="1" rowspan="1" 
class="confluenceTh"><p>Typical use</p></th></tr><tr><td colspan="1" 
rowspan="1" class="confluenceTd"><p>prepareForRender</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Render</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Before rendering the form</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Load an entity from a database to be 
edited</p></td></tr><tr><td colspan="1" rowspan="1" 
class="confluenceTd"><p>prepare</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Render</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Before rendering the form, but after 
<em>prepareForRender</em></p></td><td colspan="1" rowspan="1" 
class="confluenceTd
 "><p>&#160;</p></td></tr><tr><td colspan="1" rowspan="1" 
class="confluenceTd"><p>prepareForSubmit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Before the submitted form is processed</p></td><td 
colspan="1" rowspan="1" class="confluenceTd"><p>&#160;</p></td></tr><tr><td 
colspan="1" rowspan="1" class="confluenceTd"><p>prepare</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Before the submitted form is processed, but after 
<em>prepareForSubmit</em></p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>&#160;</p></td></tr><tr><td colspan="1" rowspan="1" 
class="confluenceTd"><p>validate</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>After fields have been populated from submitted values 
and validated</p></td><td colspan="1" rowspan="1" class="co
 nfluenceTd"><p>Perform cross-field validation</p></td></tr><tr><td colspan="1" 
rowspan="1" class="confluenceTd"><p>validateForm</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>same as <em>validate</em></p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p><em>deprecated</em></p></td></tr><tr><td 
colspan="1" rowspan="1" class="confluenceTd"><p>failure</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>After one or more validation errors have 
occurred</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>&#160;</p></td></tr><tr><td colspan="1" rowspan="1" 
class="confluenceTd"><p>success</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>When validation has completed <em>without</em> any 
errors</p></td><td colspan="1" rowspan="1" class="confluence
 Td"><p>Save changes to the database</p></td></tr><tr><td colspan="1" 
rowspan="1" class="confluenceTd"><p>submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>After all validation (success or failure) has 
finished</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>&#160;</p></td></tr></tbody></table></div><p>Note that 
the "prepare" event is emitted during both form rendering and form 
submission.</p><h2 id="FormsandValidation-TrackingValidationErrors">Tracking 
Validation Errors</h2><p>Associated with the Form is a <a shape="rect" 
class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/ValidationTracker.html";>ValidationTracker</a>
 that tracks all the provided user input and validation errors for every field 
in the form. The tracker can be provided to the Form via the Form's tracker 
parameter, but this is rarely necessary.</p><p>The Form includes methods 
<code>is
 Valid()</code> and <code>getHasErrors()</code>, which are used to see if the 
Form's validation tracker contains any errors.</p><p>In your own logic, it is 
possible to record your own errors. Form includes two different versions of 
method <code>recordError()</code>, one of which specifies a <a shape="rect" 
class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/Field.html";>Field</a>
 (an interface implemented by all form element components), and one of which is 
for "global" errors, unassociated with any particular field.</p><h2 
id="FormsandValidation-StoringDataBetweenRequests">Storing Data Between 
Requests</h2><p></p><div class="navmenu" style="float:right; width:40%; 
background:white; margin:3px; padding:3px">
+</li></ul></div><h1 id="FormsandValidation-TheFormComponent">The Form 
Component</h1><p>The core of Tapestry's form support is the <a shape="rect" 
class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/Form.html";>Form</a>
 component. The Form component encloses (wraps around) all the other <em>field 
components</em> such as <a shape="rect" class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/TextField.html";>TextField</a>,
 <a shape="rect" class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/TextArea.html";>TextArea</a>,
 <a shape="rect" class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/Checkbox.html";>Checkbox</a>,
 etc.</p><h2 id="FormsandValidation-FormEvents">Form Events</h2><p>The Form 
component emits a number of <a shape="rect" href="component-events.html">
 component events</a>. You'll want to provide event handler methods for some of 
these.</p><p>When rendering, the Form component emits two events: first, 
"prepareForRender", then "prepare". These allow the Form's container to set up 
any fields or properties that will be referenced in the form. For example, this 
is a good place to create a temporary entity object to be rendered, or to load 
an entity from a database to be edited.</p><p>When user submits the form on the 
client, a series of steps occur on the server.</p><p>First, the Form emits a 
"prepareForSubmit" event, then a "prepare" event. These allow the container to 
ensure that objects are set up and ready to receive information from the form 
submission.</p><p>Next, all the fields inside the form are <em>activated</em> 
to pull values out of the incoming request, validate them and (if valid) store 
the changes.</p><div class="navmenu" style="float:right; width:25%; 
background:#eee; margin:3px; padding:3px">
+<p><em>For Tapestry 4 Users:</em> Tapestry 5 does not use the fragile "form 
rewind" approach from Tapestry 4. Instead, a hidden field generated during the 
render stores the information needed to process the form 
submission.</p></div>&#160;<p>After the fields have done their processing, the 
Form emits a "validate" event. This is your chance to perform any cross-form 
validation that can't be described declaratively.</p><p>Next, the Form 
determines if there have been any validation errors. If there have been, then 
the submission is considered a failure, and a "failure" event is emitted. If 
there have been no validation errors, then a "success" event is 
emitted.</p><p>Finally, the Form emits a "submit" event, for logic that doesn't 
care about success or failure.</p><div class="table-wrap"><table 
class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" 
class="confluenceTh"><p>Form Event (in order)</p></th><th colspan="1" 
rowspan="1" class="confluenceTh"><p>Phase</p></th><th colspan
 ="1" rowspan="1" class="confluenceTh"><p>When emitted (and typical 
use)</p></th><th colspan="1" rowspan="1" class="confluenceTh">Method 
Name</th><th colspan="1" rowspan="1" class="confluenceTh">@OnEvent 
Constant</th></tr><tr><td colspan="1" rowspan="1" 
class="confluenceTd"><p><strong>prepareForRender</strong></p></td><td 
colspan="1" rowspan="1" class="confluenceTd"><p>Render</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Before rendering the form (e.g. load an 
entity from a database to be edited)</p></td><td colspan="1" rowspan="1" 
class="confluenceTd">onPrepareForRender()</td><td colspan="1" rowspan="1" 
class="confluenceTd">EventConstants.PREPARE_FOR_RENDER</td></tr><tr><td 
colspan="1" rowspan="1" 
class="confluenceTd"><p><strong>prepare</strong></p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Render</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Before rendering the form, but after 
<em>prepareForRender</em></p></td><td colspan="1" rowspan="1" c
 lass="confluenceTd">onPrepare()</td><td colspan="1" rowspan="1" 
class="confluenceTd">EventConstants.PREPARE</td></tr><tr><td colspan="1" 
rowspan="1" 
class="confluenceTd"><p><strong>prepareForSubmit</strong></p></td><td 
colspan="1" rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Before the submitted form is 
processed</p></td><td colspan="1" rowspan="1" 
class="confluenceTd">onPrepareForSubmit()</td><td colspan="1" rowspan="1" 
class="confluenceTd">EventConstants.PREPARE_FOR_SUBMIT</td></tr><tr><td 
colspan="1" rowspan="1" 
class="confluenceTd"><p><strong>prepare</strong></p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>Before the submitted form is processed, but after 
<em>prepareForSubmit</em></p></td><td colspan="1" rowspan="1" 
class="confluenceTd">onPrepare()</td><td colspan="1" rowspan="1" 
class="confluenceTd">EventConstants.PREPARE</td></tr><tr><td cols
 pan="1" rowspan="1" 
class="confluenceTd"><p><strong>validate</strong></p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>After fields have been populated from submitted values 
and validated (e.g. perform cross-field validation)</p></td><td colspan="1" 
rowspan="1" class="confluenceTd">onValidate</td><td colspan="1" rowspan="1" 
class="confluenceTd">EventConstants.VALIDATE</td></tr><tr><td colspan="1" 
rowspan="1" class="confluenceTd"><p><strong>validateForm</strong></p></td><td 
colspan="1" rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>same as <em>validate (deprecated &#8211; do 
not use)<br clear="none"></em></p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><em>onValidateForm</em></td><td colspan="1" rowspan="1" 
class="confluenceTd">&#160;</td></tr><tr><td colspan="1" rowspan="1" 
class="confluenceTd"><p><strong>failure</strong></p></td><td colspan=
 "1" rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>After one or more validation errors have 
occurred</p></td><td colspan="1" rowspan="1" 
class="confluenceTd">onFailure()</td><td colspan="1" rowspan="1" 
class="confluenceTd">EventConstants.FAILURE</td></tr><tr><td colspan="1" 
rowspan="1" class="confluenceTd"><p><strong>success</strong></p></td><td 
colspan="1" rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>When validation has completed 
<em>without</em> any errors (e.g. save changes to the database)</p></td><td 
colspan="1" rowspan="1" class="confluenceTd">onSuccess()</td><td colspan="1" 
rowspan="1" class="confluenceTd">EventConstants.SUCCESS</td></tr><tr><td 
colspan="1" rowspan="1" 
class="confluenceTd"><p><strong>submit</strong></p></td><td colspan="1" 
rowspan="1" class="confluenceTd"><p>Submit</p></td><td colspan="1" rowspan="1" 
class="confluenceTd"><p>After all validation (s
 uccess or failure) has finished</p></td><td colspan="1" rowspan="1" 
class="confluenceTd">onSubmit()</td><td colspan="1" rowspan="1" 
class="confluenceTd">EventConstants.SUBMIT</td></tr></tbody></table></div><p>Note
 that the "prepare" event is emitted during both form rendering and form 
submission.</p><h2 id="FormsandValidation-HandlingEvents">Handling 
Events</h2><p>Main Article: <a shape="rect" 
href="component-events.html">Component Events</a></p><p>You handle events by 
providing methods in your page or component class, either following the 
on<strong><em>Event</em></strong>From<strong><em>Component</em></strong>() 
naming convention or using the OnEvent annotation. For example:</p><div 
class="code panel pdl" style="border-width: 1px;"><div class="codeHeader 
panelHeader pdl" style="border-bottom-width: 1px;"><b>Event Handler Using 
Naming Convention</b></div><div class="codeContent panelContent pdl">
+<pre class="brush: java; gutter: false; theme: Default" 
style="font-size:12px;">    void onValidateFromPassword() { ...}</pre>
+</div></div><p>or the equivalent using @OnEvent:</p><div class="code panel 
pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" 
style="border-bottom-width: 1px;"><b>Event Handler Using @OnEvent 
Annotation</b></div><div class="codeContent panelContent pdl">
+<pre class="brush: java; gutter: false; theme: Default" 
style="font-size:12px;">    @OnEvent(value=EventConstants.VALIDATE, 
component="password")
+    void verifyThePassword() { ...}</pre>
+</div></div><h2 id="FormsandValidation-TrackingValidationErrors">Tracking 
Validation Errors</h2><p>Associated with the Form is a <a shape="rect" 
class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/ValidationTracker.html";>ValidationTracker</a>
 that tracks all the provided user input and validation errors for every field 
in the form. The tracker can be provided to the Form via the Form's tracker 
parameter, but this is rarely necessary.</p><p>The Form includes methods 
<code>isValid()</code> and <code>getHasErrors()</code>, which are used to see 
if the Form's validation tracker contains any errors.</p><p>In your own logic, 
it is possible to record your own errors. Form includes two different versions 
of method <code>recordError()</code>, one of which specifies a <a shape="rect" 
class="external-link" 
href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/Field.html";>Field</a>
 (an interface implemented by all form element components),
  and one of which is for "global" errors, not associated with any particular 
field. If the error concerns only a single field, you should use the first 
version so that the field will be highlighted.</p><h2 
id="FormsandValidation-StoringDataBetweenRequests">Storing Data Between 
Requests</h2><p></p><div class="navmenu" style="float:right; width:40%; 
background:white; margin:3px; padding:3px">
 <div class="confluence-information-macro 
confluence-information-macro-information"><p class="title">New in Tapestry 
5.4</p><span class="aui-icon aui-icon-small aui-iconfont-info 
confluence-information-macro-icon"></span><div 
class="confluence-information-macro-body">
 <p>Starting in Tapestry 5.4, the default behavior for server-side validation 
failures is to re-render the page within the same request (rather than emitting 
a redirect). This removes the need to use a session-persistent field to store 
the validation tracker when validation failures occur.</p></div></div></div>As 
with other action requests, the result of a form submission (except when using 
<a shape="rect" href="ajax-and-zones.html">Zones</a>) is to send a redirect to 
the client, which results in a second request (to re-render the page). The 
ValidationTracker must be <a shape="rect" 
href="persistent-page-data.html">persisted</a> (generally in the HttpSession) 
across these two requests in order to prevent the loss of validation 
information. Fortunately, the default ValidationTracker provided by the Form 
component is persistent, so you don't normally have to worry about 
it.<p>However, for the same reason, the individual fields updated by the 
components should also be persisted across r
 equests, and this is something you <strong>do</strong> need to do yourself 
&#8211; generally with the @Persist annotation.</p><p>For example, a Login 
page, which collects a user name and a password, might look like:</p><div 
class="code panel pdl" style="border-width: 1px;"><div class="codeContent 
panelContent pdl">
 <pre class="brush: java; gutter: false; theme: Default" 
style="font-size:12px;">package com.example.newapp.pages;


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