struts2 - How do you compare 2 struts param in a struts if -

i'm still pretty new struts , having trouble trying compare 2 struts params in struts if statement. trying find if current year param equal checkyear param

if equal want execute code. if not equal execute other code..

sample code:

<s:param name="currentyear">    <s:date name="%{new java.util.date()}" format="yyyy" /> </s:param> <s:param name="checkyear">    <s:date format="yyyy" name="#year"/> </s:param> <s:if test="${checkyear == legendyear}">   code executed </s:if> 

i don't understand purpose of '$','%', or '{}' in test part of if statement if or how need apply have check params.

thank in advance!

inside struts2 tags, use ognl. refer small language guide see how works.

in ognl, %{} means want force evaluation of expression; needed somewhere, while superfluos somewhere else. in <s:if/>, not needed, because test="" evaluate content default.

${} not exists in ognl, jsp el. search on stackoverflow nice answer on if curious.

{} alone in ognl list projection... don't need now.