How do I add a servlet filter to Nexus request processing?

The following article applies to Nexus 2.8+.

In old Nexus versions, this was done by editing web.xml.

In Nexus 2.8 and greater, this has changed.

You'll need to write a Nexus plugin which adds a Guice module. A good example that demonstrates this is:

https://github.com/sonatype/nexus-oss/blob/nexus-2.8.x/plugins/basic/nexus-content-plugin/src/main/java/org/sonatype/nexus/content/internal/ContentModule.java