A default startup Spring MVC with Apache Tiles application has a list of predefined tagx files. I find a variable ${param} is used everywhere but couldn't find there it defined and initiated, please anyone can give a hint about where does it come from? Thanks
For example, from language.tagx:
<jsp:directive.attribute name="locale" type="java.lang.String" required="true" rtexprvalue="true" description="The locale for the language to be added." />
<jsp:directive.attribute name="label" type="java.lang.String" required="true" rtexprvalue="true" description="The country label for the language to be added." />
<jsp:directive.attribute name="render" type="java.lang.Boolean" required="false" rtexprvalue="true" description="Indicate if the contents of this tag and all enclosed tags should be rendered (default 'true')" />
<c:if test="${empty render or render}">
<spring:url var="img" value="/images/${locale}.png" />
<spring:url var="url" value="">
<c:if test="${null ne param.form}">
<spring:param name="form" value="1" />
</c:if>
<c:if test="${not empty param.find}">
<spring:param name="find" value="${param.find}" />
</c:if>
<spring:param name="lang" value="${locale}" />
<c:if test="${not empty param.page}">
<spring:param name="page" value="${param.page}" />
</c:if>
<c:if test="${not empty param.size}">
<spring:param name="size" value="${param.size}" />
</c:if>
</spring:url>
<spring:message code="global_language_switch" arguments="${label}" var="lang_label" htmlEscape="false" />
<a href="${url}" title="${fn:escapeXml(lang_label)}">
<img class="flag" src="${fn:escapeXml(img)}" alt="${fn:escapeXml(lang_label)}" />
</a>
<c:out value=" " />
</c:if>
