Apache Struts 2 Documentation > Home > Guides > Tag Developers Guide > Struts Tags > Tag Reference > Generic Tag Reference > param |
Please make sure you have read the Tag Syntax document and understand how tag attribute syntax works. |
This tag can be used to parameterize other tags.
The include tag and bean tag are examples of such tags.The parameters can be added with or without a name as key. If the tag provides a name attribute the parameters are added using the {@link Component#addParameter(String, Object) addParamter} method. For unnamed parameters the Tag must implement the UnnamedParametric interface defined in this class (e.g. The TextTag does this).
This tag has the following two paramters.
Note:
When you declare the param tag, the value can be defined in either a value attribute or
as text between the start and end tag. Struts behaves a bit different according to these two situations.
This is best illustrated using an example:
<param name="color">blue</param> <-- (A) -->
<param name="color" value="blue"/> <-- (B) -->
In the first situation (A) the value would be evaluated to the stack as a java.lang.String object.
And in situation (B) the value would be evaluated to the stack as a java.lang.Object object.
For more information see WW-808.
Name |
Required |
Default |
Evaluated |
Type |
Description |
---|---|---|---|---|---|
id | false | true | String | id for referencing element. For UI and form tags it will be used as HTML id attribute | |
name | false | true | String | Name of Parameter to set | |
value | false | The value of evaluating provided name against stack | true | String | Value expression for Parameter to set |
<pre> <ui:component> <ui:param name="key" value="[0]"/> <ui:param name="value" value="[1]"/> <ui:param name="context" value="[2]"/> </ui:component> </pre>
where the key will be the identifier and the value the result of an OGNL expression run against the current ValueStack.