什么是< required>和< rtexprvalue>用于? [英] What are <required> and <rtexprvalue> used for?
问题描述
我正在研究自定义标记库,我很困惑< required>
和< rtexprvalue>
标签在TLD文件中用于定义自定义标签属性。
- 这些标签是什么?
- 我们应该在它们之间写什么?
- 写完这些标签后会有什么行为?
必需
非常简单地暗示它所说的内容。该属性是必需的或必需的。
rtexprvalue
表示运行时表达式值。这意味着该属性可以支持scriptlet值。
elexprvalue
表示它可以支持EL(表达式语言)值。 / p>
因此,如果您将 requiredattr
定义为 required = true
和 rtexprvalue = true
和 elattribute
定义为 elexprvalue = true
,您可以写如下:
< myprefix:mytag requiredattr =<%= baz.getId( )%>中elattribute = $ {foo.bar}/>
I was working on custom tag libraries and I was confused how the <required>
and <rtexprvalue>
tags are used in the TLD file to define a custom tag attribute.
- What are these tags?
- What should we write in-between them?
- What behavior do we get after writing these tags?
required
quite simply implies what it says. The attribute is required or mandatory.
rtexprvalue
means Runtime Expression Value. It means the attribute can support scriptlet values.
elexprvalue
means it can support EL (expression language) values.
So, if you have requiredattr
defined as both required=true
and rtexprvalue=true
and elattribute
is defined as elexprvalue=true
, you can write as follows:
<myprefix:mytag requiredattr="<%=baz.getId()%>" elattribute="${foo.bar}"/>
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