如何将 JSTL 标记的返回值返回到 EL 语句中？
基本上我有一个自定义标签来为我处理查询 java 对象。
<c:set var="profit">
<ct:get-profit transaction="${transaction}"/>
</c:set>
现在的问题是我想使用该值（它是 if 语句中的一个浮点数，我这样做：
<c:when test="${profit > 0}">
当我这样做时，虽然我最终得到了以下错误。
javax.el.ELException: Cannot convert -141.75 of type class java.lang.String to class java.lang.Long
我不知道如何才能完成这项工作我的印象是 JSTL 会为你处理选角，这是错误的吗？谢谢，你会如何制作这个作品？
Basically I have a custom tag that handles querying a java object for me.
<c:set var="profit">
<ct:get-profit transaction="${transaction}"/>
</c:set>
Now the problem is that I want to use that value (which is a float in an if statement, which I do as so:
<c:when test="${profit > 0}">
When I do that though I end up getting the following error.
javax.el.ELException: Cannot convert -141.75 of type class java.lang.String to class java.lang.Long
I have no idea how I can make this work. I was under the impression that JSTL's would handle casting for you, is that incorrect? Either way, how would you go about making this work? Thanks
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您可以尝试使用
0.00而不是0吗？您必须这样做的原因是因为 EL 解析器将 0 视为 Long。然而，“0.00”被视为浮点数。
Can you try doing
0.00instead of0?<c:when test="${profit > 0.00}">.The reason you have to it is because 0 is getting treated as Long by the EL parser. However, "0.00" is getting treated as a float.
您在
Object#toString()< 隐式转换为String/代码>。您希望使用其value属性来保持类型不变。我建议用 EL 函数替换
有关
如何配置此类功能的更详细示例，请检查 这个答案。
Everything which you set in the body of
<c:set>is implicitly converted toStringbyObject#toString(). You'd like to use itsvalueattribute instead which keeps the type unchanged.I'd suggest to replace the
<ct:get-profit>tag by an EL function. Since this tag doesn't seem to render any markup, you could do it as good (and better) with an EL function.in combination with
For a more detailed example how to configure such a function, check the bottom of this answer.