如何使用 WAR 中的注释定义 servlet 过滤器的执行顺序 [英] How to define servlet filter order of execution using annotations in WAR

问题描述

如果我们在 WAR 自己的 web.xml 中定义 webapp 特定的 servlet 过滤器，那么过滤器的执行顺序将与它们在 web 中定义的顺序相同.xml.

If we define webapp specific servlet filters in WAR's own web.xml, then the order of execution of the filters will be the same as the order in which they are defined in the web.xml.

但是，如果我们使用@WebFilter注解定义这些过滤器，过滤器的执行顺序是什么，我们如何确定执行顺序?

But, if we define those filters using @WebFilter annotation, what is the order of execution of filters, and how can we determine the order of execution?

推荐答案

您确实不能使用 @WebFilter 注释.但是，为了尽量减少 web.xml 的使用，只需使用 filterName 注释所有过滤器就足够了，这样您就不需要 定义，但只是按所需顺序的 定义.

You can indeed not define the filter execution order using @WebFilter annotation. However, to minimize the web.xml usage, it's sufficient to annotate all filters with just a filterName so that you don't need the <filter> definition, but just a <filter-mapping> definition in the desired order.

例如

@WebFilter(filterName="filter1")
public class Filter1 implements Filter {}

@WebFilter(filterName="filter2")
public class Filter2 implements Filter {}

在 web.xml 中是这样的:

<filter-mapping>
    <filter-name>filter1</filter-name>
    <url-pattern>/url1/*</url-pattern>
</filter-mapping>
<filter-mapping>
    <filter-name>filter2</filter-name>
    <url-pattern>/url2/*</url-pattern>
</filter-mapping>

如果您想将 URL 模式保留在 @WebFilter 中，那么您可以这样做，

If you'd like to keep the URL pattern in @WebFilter, then you can just do like so,

@WebFilter(filterName="filter1", urlPatterns="/url1/*")
public class Filter1 implements Filter {}

@WebFilter(filterName="filter2", urlPatterns="/url2/*")
public class Filter2 implements Filter {}

但是您仍然应该将 保留在 web.xml 中，因为它是 XSD 所必需的，尽管它可以为空:

but you should still keep the <url-pattern> in web.xml, because it's required as per XSD, although it can be empty:

<filter-mapping>
    <filter-name>filter1</filter-name>
    <url-pattern />
</filter-mapping>
<filter-mapping>
    <filter-name>filter2</filter-name>
    <url-pattern />
</filter-mapping>

无论采用何种方法，在 Tomcat 7.0.28 之前，这一切都将失败，因为它会因 而没有 的存在而窒息.另请参阅 使用 Tomcat，@WebFilter 不适用于 <filter-mapping>在 web.xml 中

Regardless of the approach, this all will fail in Tomcat until version 7.0.28 because it chokes on presence of <filter-mapping> without <filter>. See also Using Tomcat, @WebFilter doesn't work with <filter-mapping> inside web.xml

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