使用变量作为键访问EL中的映射值 [英] Access map value in EL using a variable as key

问题描述

我在EL中有一个Map作为${map}，我试图使用一个键来获取它的值，该键本身也是一个EL变量${key}，其值是"1000".

I have a Map in EL as ${map} and I am trying to get the value of it using a key which is by itself also an EL variable ${key} with the value "1000".

使用${map["1000"]}可以，但是${map["$key"]}无效.我在做什么错?如何使用变量作为键来获取Map值?

Using ${map["1000"]} works, but ${map["$key"]} does not work. What am I doing wrong and how can I get the Map value using a variable as key?

推荐答案

$不是变量名的开头，它表示表达式的开头.您应该使用${map[key]}来访问地图map中的属性key.

$ is not the start of a variable name, it indicates the start of an expression. You should use ${map[key]} to access the property key in map map.

您可以在带有GET参数的页面上尝试使用以下查询字符串，例如?whatEver=something

You can try it on a page with a GET parameter, using the following query string for example ?whatEver=something

<c:set var="myParam" value="whatEver"/>
whatEver: <c:out value="${param[myParam]}"/>

这将输出:

whatEver: something

请参阅: https://stackoverflow.com/tags/el/info 并滚动到括号符号"部分.

See: https://stackoverflow.com/tags/el/info and scroll to the section "Brace notation".

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