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
.
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?
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.
For example,
@WebFilter(filterName="filter1")
public class Filter1 implements Filter {}
@WebFilter(filterName="filter2")
public class Filter2 implements Filter {}
with in web.xml
just this:
<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>
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 {}
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>
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