java <% ... %> 和 <%! ... %> 在 jsp 中
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What is the difference between <% ... %> and <%! ... %> in jsp
提问by Yanki Twizzy
I am adding some more functionality to a page that has the two tags mentioned in the title. I noticed that the variable I declare in <% ... %>cannot be used in <%! ... %>and vice versa. What is the difference between the two and how can I declare variables that could be used in the two tags
我正在向具有标题中提到的两个标签的页面添加更多功能。我注意到我声明的变量<% ... %>不能用于，<%! ... %>反之亦然。两者有什么区别，我如何声明可以在两个标签中使用的变量
回答by skaffman
<% ... %>is used to embed some java code within the main service()method of the JSP. It is executed during the rendering of the page.
<% ... %>用于service()在 JSP的 main方法中嵌入一些 java 代码。它在页面渲染期间执行。
<%! ... %>is used to define code outsideof the flow of the page, and therefore outside the main service()method. Typically, this was used to define utility methods that would be called from within a <% ... %>block.
<%! ... %>用于在页面流之外定义代码，因此在 mainservice()方法之外。通常，这用于定义将从<% ... %>块内调用的实用程序方法。
Both approaches are now obsolete, however. JSP EL, JSTL and tag classes are the preferred way of doing the same thing.
然而，这两种方法现在都已过时。JSP EL、JSTL 和标签类是做同样事情的首选方式。
