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Be sure to read the Tag Syntax document to learn how tag attribute syntax works.

Generic Tags

Generic tags are used for controlling the execution flow when the pages render. These tags also allow for data extraction from places other than your action or the value stack, such as Internationalization, JavaBeans, and including additional URLs or action executions.

1. Control Tags provide control flow, such as if, else, and iterator.
2. Data Tags allow for data manipulation or creation, such as bean, push, and i18n.

UI Tags

Unlike generic tags, UI tags do not provide much control structure or logic. Rather, they are focussed on using data, either from your action/value stack or from the Data Tags, and displaying data in rich and reusable HTML. All UI tags are driven by templates and themes. While generic tags simply output some content directly from the tag (if there is any content to output), the UI tags defer to a template, often grouped together as a theme, to do the actual rendering.

Template support allows UI tags to build a rich set of reusable HTML components that can be customized to fit exact requirements. For details, see Themes and Templates.

Language Specific Tag Support

The framework strives to support multiple development environments. The framework does not impose a single template language. Almost any common language can be used, and there are hooks for new languages. By default, almost every single tag is supported in JSP, Velocity, and FreeMarker. In each of these sections, you'll find examples and techniques for applying the generic tag reference toward your specific language or template choice.

• JSP Tags
• Velocity Tags
• FreeMarker Tags

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 UI 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.

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

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

{snippet:id=templateRelatedAttributes|javadoc=true|url=org.apache.struts2.components.UIBean}

Javascript-Related Attributes

{snippet:id=javascriptRelatedAttributes|javadoc=true|url=org.apache.struts2.components.UIBean}

Tooltip Related Attributes

{snippet:id=tooltipattributes|javadoc=true|url=org.apache.struts2.components.UIBean}

General Attributes

{snippet:id=generalAttributes|javadoc=true|url=org.apache.struts2.components.UIBean}

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.

...

<@s.form action="updateAddress">
    <@saf.textfield label="Postal Code" name="postalCode" value="%{postalCode}"/>
    ...
</@s.form>

FAQs

• Why do the form tags put table tags around controls?
• How can I put a String literal in a Javascript call, for instance in an onChange attribute?
• Why won't the 'if' tag evaluate a one char string?
• Why does FreeMarker complain that there's an error in my user-directive when I used JSP Tag?
• Can an action tag run another method apart from the default execute method?
• Why didn't my action tag get executed when I have validation errors?
• Why are request parameters appended to our hyperlinks?

Resources

• Creating a UI Component in Struts 2 (Mark Menard)
• Struts 2 Tags (Rose India)

Next: Generic Tags

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.

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<@s.form action="updateAddress">
    <@s.textfield label="Postal Code" name="postalCode"/>
    ...
</@s.form>

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.

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

{snippet:id=tooltipdescription|javadoc=true|url=org.apache.struts2.components.UIBean}

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