java JSP 全局变量
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JSP global variable
提问by tinti
I have this code
我有这个代码
<%!
public String class_name = "";
%>
<c:choose>
<c:when test="${WCParam.categoryId != null}">
<% class_name = "my_account_custom"; %>
</c:when>
<c:otherwise>
<% class_name = "my_account_custom_3"; %>
</c:otherwise>
</c:choose>
<p>Class name = <c:out value='${class_name}' /></p>
WCParam.categoryId is null or not But my class_name variable is always empty. What i am doing wrong Thanks
WCParam.categoryId 是否为空但我的 class_name 变量始终为空。我做错了什么谢谢
回答by axtavt
Scriptlets (<%...%>) and expression language (${...}) are completely different things, therefore their variables belong to different scopes (variables used in EL expressions are actually request attributes of different scopes).
Scriptlets( <%...%>)和表达式语言( ${...})是完全不同的东西，因此它们的变量属于不同的作用域（EL表达式中使用的变量实际上是不同作用域的请求属性）。
If you decalred class_nameas a scriptlet variable, you should access it using scriptlet as well:
如果你被标记class_name为一个 scriptlet 变量，你也应该使用 scriptlet 访问它：
<p>Class name = <c:out value='<%=class_name%>' /></p>
However, you can write it without using a variable at all:
但是，您可以完全不使用变量来编写它：
<p>Class name = <c:out
value='${WCParam.categoryId != null ? "my_account_custom" : "my_account_custom3"}' /></p>
