java 从自定义 JSP 标签访问请求对象
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Accessing Request object from custom JSP tags
提问by Lotus Notes
I'm trying to make a set of custom tags that encapsulate form elements (markup and validation).
我正在尝试制作一组封装表单元素（标记和验证）的自定义标签。
There's a method given to retrieve the "Out" object easily:
有一种方法可以轻松检索“Out”对象：
JspWriter out = getJspContext().getOut();
However I can't figure out how to get the request object. I want to be able to directly access the submitted form values from within the Tag class so that I can validate each field.
但是我不知道如何获取请求对象。我希望能够从 Tag 类中直接访问提交的表单值，以便我可以验证每个字段。
The documentationis quite sparse, so I thought maybe I could use the JspContextobject to somehow get the request attributes. But I don't understand the different scopes.
该文件是相当稀疏，所以我想也许我可以使用的JspContext对象以某种方式获得请求的属性。但我不明白不同的范围。
System.out.println(getJspContext().findAttribute("field1"));
always prints "null".
总是打印“null”。
Enumeration e = getJspContext().getAttributeNamesInScope(1);
Looping through and printing out the enumeration just gives me a list of classes that don't exist:
循环并打印出枚举只会给我一个不存在的类的列表：
javax.servlet.jsp.jspOut
javax.servlet.jsp.jspPage
javax.servlet.jsp.jspSession
javax.servlet.jsp.jspApplication
javax.servlet.jsp.jspPageContext
javax.servlet.jsp.jspConfig
javax.servlet.jsp.jspResponse
javax.servlet.jsp.jspRequest
So is this even possible?
那么这可能吗？
If not, could anyone point me to a tag library that deals with form display and validation? I searched the internet for a couple hours and it seemed every single one was discontinued and I couldn't download them. Either that or suggest a better alternative for handling forms.
如果没有，有人能指点我一个处理表单显示和验证的标签库吗？我在互联网上搜索了几个小时，似乎每一个都停产了，我无法下载它们。或者建议一个更好的处理表单的替代方法。
Edit: The tags extend the SimpleTagSupportclass.
编辑：标签扩展了SimpleTagSupport类。
回答by Fil
If your class is extending TagSupport, you can access the protected pageContext variable. From that you're able to retrieve the request object.
如果您的类正在扩展 TagSupport，您可以访问受保护的 pageContext 变量。从中您可以检索请求对象。
http://java.sun.com/webservices/docs/1.5/api/javax/servlet/jsp/tagext/TagSupport.html#pageContext
http://java.sun.com/webservices/docs/1.5/api/javax/servlet/jsp/tagext/TagSupport.html#pageContext
