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Apache Struts 2 Documentation
Form Tags
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Please make sure you have read the Tag Syntax document and understand how tag attribute syntax works.

Within the form tags, there are two classes of tags: the form tag itself, and all other tags, which make up the individual form elements. The behavior of the form tag is different than the elements enclosed within it.

## Form Tag Themes

As explained in Themes and Templates, the HTML Tags (which includes Form Tags) are all driven by templates. Templates are grouped together to create themes. The framework bundles three themes in the distribution.

simple | Sometimes too simple
xhtml | Extends simple | (default)
ajax | Extends xhtml

The predefined themes can be used "as is" or customized.

xhtml layout

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The xhtml theme renders out a two-column table. If a different layout is needed, do not write your own HTML. Create a new theme or utilize the simple theme.

### Simple theme caveats

The downside of using the simple theme is that it doesn't support as many of the attributes that the other themes do. For example, the `label` attribute does nothing in the simple theme, and the automatic display of error messages is not supported.

## Common Attributes

All the form tags extend the UIBean class. This base class provides a set of common attributes, that can be grouped in to three categories: `templated-related`, javascript-related, and general attributes. The individual attributes are documented on each tag's reference page.

In addition to the common attributes, a special attribute exists for all form element tags: `form` (${parameters.form}). The `form` property represents the attributes used to render the form tag, such as the form's id. In a template, the form's ID can be found by calling ${parameters.form.id}.

## Template-Related Attributes

Attribute | Theme | Data Types | Description
templateDir | n/a | String | define the template directory
theme | n/a | String | define the theme name
template | n/a | String | define the template name
themeExpansionToken | n/a | String | special token (defined with struts.ui.theme.expansion.token) used to search for template in parent theme (don't use it separately!)
expandTheme | n/a | String | concatenation of themeExpansionToken and theme which tells internal template loader mechanism to try load template from current theme and then from parent theme (and parent theme, and so on) when used with <#include/> directive

## Javascript-Related Attributes

Attribute | Theme | Data Types | Description
onclick | simple | String | html javascript onclick attribute
ondblclick | simple | String | html javascript ondbclick attribute
onmousedown | simple | String | html javascript onmousedown attribute
onmouseup | simple | String | html javascript onmouseup attribute
onmouseover | simple | String | html javascript onmouseover attribute
onmouseout | simple | String | html javascript onmouseout attribute
onfocus | simple | String | html javascript onfocus attribute
onblur | simple | String | html javascript onblur attribute
onkeypress | simple | String | html javascript onkeypress attribute
onkeyup | simple | String | html javascript onkeyup attribute
onkeydown | simple | String | html javascript onkeydown attribute
onselect | simple | String | html javascript onselect attribute
onchange | simple | String | html javascript onchange attribute

## Tooltip Related Attributes

Attribute | Data Type | Default | Description
tooltip | String | none | Set the tooltip of this particular component
jsTooltipEnabled | String | false | Enable js tooltip rendering
tooltipIcon | String | /struts/static/tooltip/tooltip.gif | The url to the tooltip icon
tooltipDelay | String | 500 | Tooltip shows up after the specified timeout (miliseconds). A behavior similar to that of OS based tooltips.
key | simple | String | The name of the property this input field represents. This will auto populate the name, label, and value

## General Attributes

Attribute | Theme | Data Types | Description
cssClass | simple | String | define html class attribute
cssStyle | simple | String | define html style attribute
cssClass | simple | String | error class attribute
cssStyle | simple | String | error style attribute
title | simple | String | define html title attribute
disabled | simple | String | define html disabled attribute
label | xhtml | String | define label of form element
labelPosition | xhtml | String | define label position of form element (top/left), default to left
requiredPosition | xhtml | String | define required label position of form element (left/right), default to right
errorPosition | xhtml | String | define error position of form element (top|bottom), default to top
name | simple | String | Form Element's field name mapping
required | xhtml | Boolean | add * to label (true to add false otherwise)
tabIndex | simple | String | define html tabindex attribute
value | simple | Object | define value of form element

When some attributes don't apply

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Some tag attributes may not be utilized by all, or any, of the templates. For example, the form tag supports the `tabindex` attribute, but none of the themes render the `tabindex`.

## Value/Name Relationship

In many of the tags (except for the form tag) there is a unique relationship between the `name` and `value` attributes. The `name` attribute provides the name for the tag, which in turn is used as the control attribute when the form is submitted. The value submitted is bound to the `name`. In most cases, the `name` maps to a simple JavaBean property, such as "postalCode". On a submit, the value would be set to the property by calling the `setPostalCode` mutator.

Likewise, a form control could be populated by calling a JavaBean accessor, like `getPostalCode`. In the expression language, we can refer to the JavaBean property by name. An expression like "%{postalCode}" would in turn call `getPostalCode`.

Using Expressions to populate a form for editing

However, since the tags imply a relationship between the `name` and `value`, the `value` attribute is optional. If a `value` is not specified, by default, the JavaBean accessor is used instead.

Populating a form for editing, the easy way

While most attributes are exposed to the underlying templates as the same key as the attribute (${parameters.label}), the `value` attribute is not. Instead, it can be accessed via the `nameValue` key (${parameters.nameValue}). The `nameValue` key indicates that the value may have been generated from the `name` attribute rather than explicitly defined in the `value` attribute.

## ID Name Assignment

All form tags automatically assign an ID to the control, but the ID can be overridden if needed.

Forms | The default ID is the action name. For example, "updateAddress".
Controls | The default ID is the form's name concatenated with the tag name. For example, "updateAddress_postalCode".

## Required Attribute

The `required` attribute on many UI tags defaults to true only if you have client-side validation enabled, and a validator is associated with that particular field.

## Tooltip

tooltipConfig is deprecated, use individual tooltip configuration attributes instead

Every Form UI component (in xhtml / css_xhtml or any other that extends them) can have tooltips assigned to them. The Form component's tooltip related attribute, once defined, will be applied to all form UI components that are created under it unless explicitly overriden by having the Form UI component itself defined with their own tooltip attribute.

In Example 1, the textfield will inherit the tooltipDelay and tooltipIconPath attribte from its containing form. In other words, although it doesn't define a tooltipIconPath attribute, it will have that attribute inherited from its containing form.

In Example 2, the textfield will inherite both the tooltipDelay and tooltipIconPath attribute from its containing form, but the tooltipDelay attribute is overriden at the textfield itself. Hence, the textfield actually will have its tooltipIcon defined as /myImages/myIcon.gif, inherited from its containing form, and tooltipDelay defined as 5000.

Example 3, 4 and 5 show different ways of setting the tooltip configuration attribute.
Example 3: Set tooltip config through the body of the param tag
Example 4: Set tooltip config through the value attribute of the param tag
Example 5: Set tooltip config through the tooltip attributes of the component tag

## Next: UI Tag Reference