logic (<p><strong>Note: Some of the features in this taglib are also available in the <a href="http://java.sun.com/products/jsp/jstl/">JavaServer Pages Standard Tag Library (JSTL)</a>. The Struts team encourages the use of the standard tags over the Struts specific tags when possible.</strong></p> <p>This tag library contains tags that are useful in managing conditional generation of output text, looping over object collections for repetitive generation of output text, and application flow management.</p> <p>For tags that do value comparisons (<code>equal</code>, <code>greaterEqual</code>, <code>greaterThan</code>, <code>lessEqual</code>, <code>lessThan</code>, <code>notEqual</code>), the following rules apply:</p> <ul> <li>The specified value is examined. If it can be converted successfully to a <code>double</code> or a <code>long</code>, it is assumed that the ultimate comparison will be numeric (either floating point or integer). Otherwise, a String comparison will be performed.</li> <li>The variable to be compared to is retrieved, based on the selector attribute(s) (<code>cookie</code>, <code>header</code>, <code>name</code>, <code>parameter</code>, <code>property</code>) present on this tag. It will be converted to the appropriate type for the comparison, as determined above.</li> <li>If the specified variable or property returns null, it will be coerced to a zero-length string before the comparison occurs.</li> <li>The specific comparison for this tag will be performed, and the nested body content of this tag will be evaluated if the comparison returns a <code>true</code> result.</li> </ul> <p>For tags that do substring matching (<code>match</code>, <code>notMatch</code>), the following rules apply:</p> <ul> <li>The specified variable is retrieved, based on the selector attribute(s) (<code>cookie</code>, <code>header</code>, <code>name</code>, <code>parameter</code>, <code>property</code>) present on this tag. The variable is converted to a String, if necessary.</li> <li>A request time exception will be thrown if the specified variable cannot be retrieved, or has a null value.</li> <li>The specified value is checked for existence as a substring of the variable, in the position specified by the <code>location</code> attribute, as follows: at the beginning (if location is set to <code>start</code>), at the end (if location is set to <code>end</code>), or anywhere (if location is not specified).</li> </ul> <p>Many of the tags in this tag library will throw a <code>JspException</code> at runtime when they are utilized incorrectly (such as when you specify an invalid combination of tag attributes). JSP allows you to declare an "error page" in the <code>&lt;%@ page %&gt;</code> directive. If you wish to process the actual exception that caused the problem, it is passed to the error page as a request attribute under key <code>org.apache.struts.action.EXCEPTION</code>.</p>)
logic

Tags logic:empty logic:equal logic:forward logic:greaterEqual logic:greaterThan logic:iterate logic:lessEqual logic:lessThan logic:match logic:messagesNotPresent logic:messagesPresent logic:notEmpty logic:notEqual logic:notMatch logic:notPresent logic:present logic:redirect