Can someone tell me what is the difference between spring saml extension and spring security 5 saml. I found like configs are less in spring security 5.
Spring Security SAML extension is not actively developed.
The Spring Security team opted to provide framework support for SAML 2 authentication as part of core Spring Security, which is available since version 5.2.0.
As you stated, not all feature functionality exists in Spring Security core yet.
From the Spring Security documentation
SAML 2 Service Provider, SP a.k.a. a relying party, support existed as an independent project since 2009. The 1.0.x branch is still in use, including in the Cloud Foundry User Account and Authentication Server that also created a SAML 2.0 Identity Provider implementation based on the SP implementation.
In 2018 we experimented with creating an updated implementation of both a Service Provider and Identity Provider as a standalone library. After careful, and lengthy, deliberation we, the Spring Security team, decided to discontinue that effort. While this effort created a replacement for that standalone 1.0.x library we didn’t feel that we should build a library on top of another library.
Instead we opted to provide framework support for SAML 2 authentication as part of core Spring Security instead.
From the Spring Security SAML GitHub
This project is being rewritten.
...
we will not be publishing any official releases of the 2.0.0 milestones, but will maintain it until all feature functionality that exists in the milestones are part of Spring Security.
We continue to accept pull request for the 1.0.x branch, but are not actively developing it.