Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Attributes of a Composite Component

A composite component is a special type of JavaServer Faces template that acts as a component. If you are new to composite components, see Composite Components before you proceed with this chapter.

You define an attribute of a composite component by using the `composite:attribute` tag. Table 14-1 lists the commonly used attributes of this tag.

Table 14-1 Commonly Used Attributes of the composite:attribute Tag

Attribute | Description
`name` | Specifies the name of the composite component attribute to be used in the using page. Alternatively, the `name` attribute can specify standard event handlers such as `action`, `actionListener`, and managed bean.
`default` | Specifies the default value of the composite component attribute.
`required` | Specifies whether it is mandatory to provide a value for the attribute.
`method-signature` | Specifies a subclass of `java.lang.Object` as the type of the composite component’s attribute. The `method-signature` element declares that the composite component attribute is a method expression. The `type` attribute and the `method-signature` attribute are mutually exclusive. If you specify both, `method-signature` is ignored. The default type of an attribute is `java.lang.Object.` Note: Method expressions are similar to value expressions, but rather than supporting the dynamic retrieval and setting of properties, method expressions support the invocation of a method of an arbitrary object, passing a specified set of parameters and returning the result from the called method (if any).
`type` | Specifies a fully qualified class name as the type of the attribute. The `type` attribute and the `method-signature` attribute are mutually exclusive. If you specify both, `method-signature` is ignored. The default type of an attribute is `java.lang.Object.`

The following code snippet defines a composite component attribute and assigns it a default value:

    <composite:attribute name="username" default="admin"/>

The following code snippet uses the `method-signature` element:

    <composite:attribute name="myaction"
                         method-signature="java.lang.String action()"/>

The following code snippet uses the `type` element:

    <composite:attribute name="dateofjoining" type="java.util.Date"/>

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