Migrate Groovy to Java

[rwinch]

Summary

The tests that are written in Groovy are very convenient and easy to read, but place an unnecessary burden on contributors unfamiliar with Groovy. We should migrate the Groovy tests to Java.

For the samples using Geb, take a look at https://github.com/spring-projects/spring-security/tree/b9152701a65df5b3fa78fe4bd2a946018f9ca352/samples/javaconfig/webflux-form/src/integration-test/java/sample

The following commits in Spring Session might be useful as well

spring-projects/spring-session@1a318b8

and

spring-projects/spring-session@8e7c736

Anyone taking on this task I'd encourage them to break it up into multiple PRs that migrate smaller portions at a time (i.e. a sample or a package) and include

Migrate <what is migrated> groovy->java

(optional additional details)

Issue: gh-4939

I'd also encourage contributors to comment on this issue to state which piece they are going to start working on migrating. This will allow multiple people to help tackle this large issue and avoid duplicating efforts.

[michael-simons]

Next: xml-jaas

[michael-simons]

Next: javaconfig-form

[adolfoweloy]

Migrate UserDetailsManagerConfigurerTests test groovy->java from security-config #4949

[michael-simons]

Next: javaconfig-jdbc