在Scriptlet中访问JSTL/EL变量 [英] Accessing a JSTL / EL variable inside a Scriptlet

问题描述

以下代码会导致错误:

<c:set var="test" value="test1"/>
<%
    String resp = "abc"; 
    resp = resp + ${test};  //in this line I got an  Exception.
    out.println(resp);
%>

为什么我不能在小脚本中使用表达语言"$ {test}"?

Why can't I use the expression language "${test}" in the scriptlet?

推荐答案

JSTL 变量实际上是属性，默认情况下在页面上下文级别范围内.
因此，如果您需要在scriptlet中访问JSTL变量值，则可以通过调用

JSTL variables are actually attributes, and by default are scoped at the page context level.
As a result, if you need to access a JSTL variable value in a scriptlet, you can do so by calling the getAttribute() method on the appropriately scoped object (usually pageContext and request).

resp = resp + (String)pageContext.getAttribute("test"); 

完整代码

 <c:set var="test" value="test1"/>
 <%
    String resp = "abc"; 
    resp = resp + (String)pageContext.getAttribute("test");   //No exception.
    out.println(resp);
  %>  

但是为什么会出现这种异常.

But why that exception come to me.

JSP脚本用于包含任何代码对页面中使用的脚本语言有效的片段.脚本的语法如下:

A JSP scriptlet is used to contain any code fragment that is valid for the scripting language used in a page. The syntax for a scriptlet is as follows:

<%
   scripting-language-statements
%>

将脚本语言设置为Java时，脚本小程序将转换为Java编程语言语句片段，并将其插入JSP页面Servlet的服务方法中.

When the scripting language is set to Java, a scriptlet is transformed into a Java programming language statement fragment and is inserted into the service method of the JSP page’s servlet.

在scriptlet中，您可以编写Java代码，而在非Java代码中可以编写${test}.

In scriptlets you can write Java code and ${test} in not Java code.

不相关

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