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| <a href="tag-reference.html" title="back to Tag Reference"><< back to Tag Reference</a> |
| |
| <h1 id="param">param</h1> |
| |
| <p>Please make sure you have read the <a href="tag-syntax">Tag Syntax</a> document and understand how tag attribute syntax works.</p> |
| |
| <h2 id="description">Description</h2> |
| |
| <p>This tag can be used to parameterize other tags. The <code class="highlighter-rouge">include</code> tag and <code class="highlighter-rouge">bean</code> tag are examples of such tags.</p> |
| |
| <p>The parameters can be added with or without a <code class="highlighter-rouge">name</code> as key. If the tag provides a <code class="highlighter-rouge">name</code> attribute the parameters are |
| added using the <code class="highlighter-rouge">Component#addParameter(String, Object)</code> method. For unnamed parameters the tag must implement |
| the <code class="highlighter-rouge">UnnamedParametric</code> interface defined in this class (e.g. The TextTag does this).</p> |
| |
| <p>This tag has the following two parameters.</p> |
| |
| <ul> |
| <li>name (String) - the name of the parameter</li> |
| <li>value (Object) - the value of the parameter</li> |
| <li>suppressEmptyParameters (boolean) - whether to suppress this parameter if empty</li> |
| </ul> |
| |
| <blockquote> |
| <p><strong>NOTE</strong>: When you declare the param tag, the value can be defined in either a <code class="highlighter-rouge">value</code> 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: |
| <code class="highlighter-rouge"><param name="color">blue</param></code> (A) |
| <code class="highlighter-rouge"><param name="color" value="blue"/></code> (B) |
| In the first situation (A) the value would be evaluated to the stack as a <code class="highlighter-rouge">java.lang.String</code> object. And in situation |
| (B) the value would be evaluated to the stack as a <code class="highlighter-rouge">java.lang.Object</code> object. |
| For more information see <a href="https://issues.apache.org/jira/browse/WW-808">WW-808</a>.</p> |
| </blockquote> |
| |
| <p>Parametrize other tags</p> |
| |
| <h2 id="attributes">Attributes</h2> |
| |
| <table width="100%"> |
| <tr> |
| <td colspan="6"><h4>Dynamic Attributes Allowed:</h4> false</td> |
| </tr> |
| <tr> |
| <td colspan="6"> </td> |
| </tr> |
| <tr> |
| <th align="left" valign="top"><h4>Name</h4></th> |
| <th align="left" valign="top"><h4>Required</h4></th> |
| <th align="left" valign="top"><h4>Default</h4></th> |
| <th align="left" valign="top"><h4>Evaluated</h4></th> |
| <th align="left" valign="top"><h4>Type</h4></th> |
| <th align="left" valign="top"><h4>Description</h4></th> |
| </tr> |
| <tr> |
| <td align="left" valign="top">name</td> |
| <td align="left" valign="top">false</td> |
| <td align="left" valign="top"></td> |
| <td align="left" valign="top">false</td> |
| <td align="left" valign="top">String</td> |
| <td align="left" valign="top">Name of Parameter to set</td> |
| </tr> |
| <tr> |
| <td align="left" valign="top">suppressEmptyParameters</td> |
| <td align="left" valign="top">false</td> |
| <td align="left" valign="top">false</td> |
| <td align="left" valign="top">false</td> |
| <td align="left" valign="top">Boolean</td> |
| <td align="left" valign="top">Whether to suppress empty parameters</td> |
| </tr> |
| <tr> |
| <td align="left" valign="top">value</td> |
| <td align="left" valign="top">false</td> |
| <td align="left" valign="top">The value of evaluating provided name against stack</td> |
| <td align="left" valign="top">false</td> |
| <td align="left" valign="top">String</td> |
| <td align="left" valign="top">Value expression for Parameter to set</td> |
| </tr> |
| </table> |
| |
| <h2 id="examples">Examples</h2> |
| |
| <pre><code class="language-jsp"><ui:component> |
| <ui:param name="key" value="[0]"/> |
| <ui:param name="value" value="[1]"/> |
| <ui:param name="context" value="[2]"/> |
| </ui:component> |
| </code></pre> |
| |
| <p>Whether to suppress empty parameters:</p> |
| |
| <pre><code class="language-jsp"><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> |
| </code></pre> |
| |
| <p>where the key will be the identifier and the value the result of an OGNL expression run against the current ValueStack.</p> |
| |
| </section> |
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