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# param

Please make sure you have read the Tag Syntax document and understand how tag attribute syntax works.

## Description

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 `Component#addParameter(String, Object)` 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 parameters.

- name (String) - the name of the parameter
- value (Object) - the value of the parameter
- suppressEmptyParameters (boolean) - whether to suppress this parameter if empty

> 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.

Parametrize other tags

## Attributes

#### Dynamic Attributes Allowed: false
#### Name | #### Required | #### Default | #### Evaluated | #### Type | #### Description
--- | --- | --- | --- | --- | ---
name | false |  | false | String | Name of Parameter to set
performClearTagStateForTagPoolingServers | false | false | false | Boolean | Whether to clear all tag state during doEndTag() processing (if applicable)
suppressEmptyParameters | false | false | false | Boolean | Whether to suppress empty parameters
value | false | The value of evaluating provided name against stack | false | String | Value expression for Parameter to set

## Examples

    <ui:component>
     <ui:param name="key"     value="[0]"/>
     <ui:param name="value"   value="[1]"/>
     <ui:param name="context" value="[2]"/>
    </ui:component>

Whether to suppress empty parameters:

    <s:url action="eventAdd">
      <s:param name="bean.searchString" value="%{bean.searchString}" />
      <s:param name="bean.filter" value="%{bean.filter}" />
      <s:param name="bean.pageNum" value="%{pager.pageNumber}" suppressEmptyParameters="true" />
    </s:url>

where the key will be the identifier and the value the result of an OGNL expression run against the current ValueStack.

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