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如何将自定义 taglib 标签的出现限制为每页一个？

发布于 2024-11-08 16:27:11 字数 73 浏览 2 评论 0原文

例如，当我希望不可能在一页上多次出现时。

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尾戒 2024-11-15 16:27:11

每次调用该标记时，都会在页面上下文中设置一个属性。如果该属性已经存在，则意味着当前页面已调用该标签，因此抛出异常。像这样的东西（未经测试）

class MyTagLib {

   def doIt = { attrs, body ->

       if (pageScope.invoked) {
           // throwTagError is a built-in method that is available in all tag libs
           thowTagError "this tag can only be invoked once per page"
       }

       pageScope.invoked = true

      // Now cure world poverty or whatever it is that your tag is supposed to do
   }
}

Every time the tag is called, set an attribute in the page context. If the attribute is already present, that means the tag has already been called for the current page, so throw an exception. Something like this (untested)

class MyTagLib {

   def doIt = { attrs, body ->

       if (pageScope.invoked) {
           // throwTagError is a built-in method that is available in all tag libs
           thowTagError "this tag can only be invoked once per page"
       }

       pageScope.invoked = true

      // Now cure world poverty or whatever it is that your tag is supposed to do
   }
}

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