What is an ias-web.xml deployment descriptor file?

I came across a fairly old Java web application that made use of servlets and along side the web.xml file in the WEB-INF directory there was an ias-web.xml file. From googling a bit开发者_运维百科 I found it is some kind of a deployment descriptor file.

But when would you have one? Are they still in use today? Did this use to be a Java standard?

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Ias is an old App server. And like all app servers, there are default descriptors like web.xml and vendor specific files like ias-web.xml.

This comes from the fact that the JavaEE standard specifies a lot, but still leaves room for vendor specific enhancements. And those enhancements are controlled by the vendor-speficic descriptors. The counterpart of ias-web.xml on JBoss would for example be jboss-web.xml

Have a look at this guide about migration hints.