Apache Struts 2 Documentation > Home > Guides > Tag Developers Guide > Struts Tags > Tag Reference > Generic Tag Reference > param
Added by digi9ten, last edited by Ted Husted on Sep 02, 2006  (view change)
Please make sure you have read the Tag Syntax document and understand how tag attribute syntax works.

Description

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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.

  • name (String) - the name of the parameter
  • value (Object) - the value of the parameter

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. WebWork 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.

Parameters

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Name

Required

Default

Type

Description

name false   String Name of Parameter to set
value false The value of evaluating provided name against stack Object/String Value expression for Parameter to set
id false   Object/String id for referencing element. For UI and form tags it will be used as HTML id attribute

Examples

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<pre>
<ui:component>
 <ui:param name="key"     value="[0]"/>
 <ui:param name="value"   value="[1]"/>
 <ui:param name="context" value="[2]"/>
</ui:component>
</pre>
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where the key will be the identifier and the value the result of an OGNL expression run against the current OgnlValueStack.