freemarker如何獲取頁面請求的參數

用例描述:
A頁面:http://localhost:8080/Houser/newsManage.action?categoryname=402880f5122bc83801122bd89fae0005
B頁面:newsManage.ftl

在ftl頁面這樣寫:
${request.getParameter("categoryname")}

但是假如你要用<#if 指令讓${request.getParameter("categoryname")}參與比較呢？有一個小地方要注意一下：
正確寫法：
1)
     <#list pagesdatas as ls> 
      <#if ls.newscategory.id?default("") = ‘${request.getParameter("categoryname")}‘>
      .....................
      </#if>  
     </#list> 
2)
<#list pagesdatas as ls> 
      <#if ls.newscategory.id?default("") = "${request.getParameter(‘categoryname‘)}">
      .....................
      </#if>  
     </#list>

3
<#list pagesdatas as ls> 
      <#if ls.newscategory.id?default("") = "${request.getParameter(\"categoryname\")}">
      .....................
      </#if>  
     </#list> 
錯誤寫法：
     <#list pagesdatas as ls> 
      <#if ls.newscategory.id?default("") = "${request.getParameter("categoryname")}">
      .....................
      </#if>  
     </#list> 
原因:估記應該是4個雙引號衝突了

補充:把${request.getParameter("categoryname")}賦值給變量的正確寫法:
1)<#assign var ="${request.getParameter(‘categoryname‘)}">
2) <#assign var =‘${request.getParameter(‘categoryname‘)}‘>
3)<#assign var ="${request.getParameter(\"categoryname\")}">