Package org.apache.tapestry5.corelib.components

Class Label

  • @SupportsInformalParameters
public class Label
extends Object
    Generates a <label> element for a particular field. It writes the CSS class "control-label". A Label will render its body, if it has one. However, in most cases it will not have a body, and will render its field's label as its body. Remember, however, that it is the field label that will be used in any error messages. The Label component allows for client- and server-side validation error decorations.
    Component Parameters 
    NameTypeFlagsDefaultDefault Prefix
    clientIdStringSince 5.6.0 literal
    Used to explicitly set the client-side id of the element for this component. Normally this is not bound (or null) and org.apache.tapestry5.services.javascript.JavaScriptSupport#allocateClientId(org.apache.tapestry5.ComponentResources) is used to generate a unique client-id based on the component's id. In some cases, when creating client-side behaviors, it is useful to explicitly set a unique id for an element using this parameter. Certain values, such as "submit", "method", "reset", etc., will cause client-side conflicts and are not allowed; using such will cause a runtime exception.
    fororg.apache.tapestry5.FieldRequired, Not Null component
    The for parameter is used to identify the Field linked to this label (it is named this way because it results in the for attribute of the label element).
    ignoreBodyboolean  prop
    If true, then the body of the label element (in the template) is ignored. This is used when a designer places a value inside the label element for WYSIWYG purposes, but it should be replaced with a different (probably, localized) value at runtime. The default is false, so a body will be used if present and the field's label will only be used if the body is empty or blank.

    Examples

    Search.tml

    <html xmlns:t="http://tapestry.apache.org/schema/tapestry_5_0_0.xsd">
    <body>

        <t:form>
            <t:label for="search"/>
            <t:textfield t:id="search" size="50"/>

            <t:checkbox t:id="all"/>
            <t:label for="all">
                Include out of date records
            </t:label>

        . . .

</html>

    This demonstrates that the Label can come before or after the form control element component (the TextField and Checkbox components). When a Label has a body, that takes precendence over the field's label, though the field's label is what's used in any error messages.

    Notes

    The Label component is very important for user accessibility. A user will be able to click on the label to move the cursor into the corresponding field.

    The Label component supports informal parameters; this can be very useful for adding the accesskey attribute supported by most browsers.

    • Constructor Detail