OpenSAML support for Java 21

[Cantor, Scott]

> Can you please confirm if OpenSAML 4.0.1 is supported with
> Java 21 (OpenJDK) ,

OpenSAML 4 reached its end of life last July.

> we are trying to upgrade from JDK 17 to JDK 21 and seeing
> issue with java.lang.NoClassDefFoundError:
> javax/servlet/ServletOutputStream

That has nothing to do with the Java version, that's a compatibility issue with the pre-Jakarta servlet APIs, it's an EE spec version issue, not a Java one. The conversion to Jakarta and Servlet 5 was done in OpenSAML 5 and 5.1.4 is the only supported version.

-- Scott