Java 在 servlet 中获取过滤器初始化参数
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Get filter init parameters in a servlet
提问by JeffJak
I have a filter that looks like this:
我有一个看起来像这样的过滤器：
<filter>
<filter-name>TestFilter</filter-name>
<filter-class>org.TestFilter</filter-class>
<init-param>
<param-name>timeout</param-name>
<param-value>30</param-value>
</init-param>
</filter>
Since we are talking ServletFilter and Servlets. Essentially, I am already in my servlet and have executed the first part of the doFilter. So the container must know the init-parameter. I don't have access to change the Filter class.
因为我们在谈论 ServletFilter 和 Servlets。本质上，我已经在我的 servlet 中并且已经执行了 doFilter 的第一部分。所以容器必须知道 init 参数。我无权更改 Filter 类。
Is it possible to get the init-parameter value given an HttpServletRequest object?
是否可以获取给定 HttpServletRequest 对象的 init 参数值？
The only solution I can think of is to read the web.xml as a resource and try to find the value manually. But it feels like there is a better solution.
我能想到的唯一解决方案是将 web.xml 作为资源读取并尝试手动查找值。但感觉有更好的解决方案。
采纳答案by ChssPly76
Why would you need it in your servlet to begin with? Filter parameter belongs to filter. Your options are:
为什么首先需要在 servlet 中使用它？过滤器参数属于过滤器。您的选择是：
- Move said parameter to context init parameter; you'll be able to access it from both filter and servlet.
- In your filter's doFilter method set an attribute (on request) with parameter value, have you servlet read it.
- 将所述参数移动到上下文初始化参数；您将能够从过滤器和 servlet 访问它。
- 在您的过滤器的 doFilter 方法中，使用参数值设置一个属性（根据请求），让您的 servlet 读取它。
Context parameter example.
上下文参数示例。
web.xml:
网页.xml：
<context-param>
<param-name>param1</param-name>
<param-value>value</param-value>
</context-param>
your code:
你的代码：
String paramValue = getServletContext().getInitParameter("param1");
and the filter would have access to the same param value using:
并且过滤器可以使用以下方法访问相同的参数值：
String paramValue = filterConfig.getServletContext().getInitParameter("param1");
回答by ZZ Coder
If the filter is not declared final, you can extend it. For example,
如果过滤器未声明为 final，您可以扩展它。例如，
public class MyFilter extends TheirFilter {
public void init(javax.servlet.FilterConfig filterConfig)
throws javax.servlet.ServletException {
super(filterConfig);
// Retrieve the parameter here
}
}
Then change the web.xml to change the filter class to yours.
然后更改 web.xml 以将过滤器类更改为您的。
