I tested the affected classes (MethodValidationInterceptor and
LocalValidatorFactoryBean) briefly and both appear to work correctly
using libhibernate-validator-java 5.3.6-1, so I opened the MR now:
https://salsa.debian.org/java-team/libspring-java/merge_requests/2
As noted in #942507, h-v 5 does require an Expression Language (EL) impl
at runtime. For my tiny test case I used libtomcat9-embed-el and it
worked, but I am not sure if it's really valid to use that outside a
Tomcat container. It sounds like org.glassfish:el-impl is another
popular choice but it is not packaged. Again this looks like something
that has to be decided by each application (for example with webapps the
EL impl may be provided by the container e.g. Tomcat).
