如何使用WAR中的注释定义servlet过滤器执行顺序 [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 中定义特定于webapp的servlet过滤器，那么过滤器的执行顺序将与它们的定义顺序相同在 web.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定义这些过滤器注释，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

您确实无法使用定义过滤器执行顺序 @WebFilter 注释。但是，为了最小化 web.xml 的使用，仅使用 filterName 注释所有过滤器就足够了，这样你就可以了不需要< filter> 定义，只需要按所需顺序的< filter-mapping> 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 中就是这样：

<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>

如果您想将网址格式保留在 @WebFilter ，那么你可以这样做，

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 {}

但是你仍然应该保留< url-pattern> 在 web.xml 中，因为根据XSD需要它，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，这一切都将在Tomcat中失败，直到版本7.0.28，因为它会在存在时窒息< filter-mapping> 没有< filter> 。另请参阅使用Tomcat，@ WebFilter不能与< filter-mapping>一起使用在web.xml内

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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