Opensaml error receiving correct unmarshaller

I found that there is not unmarshallers register as there is not initialization in the library:

Important piece of code:

// Initialize the library
DefaultBootstrap.bootstrap();

In OpenSAML3 you have to first make sure to include the opensaml-saml-impl artifact in your dependencies, since all the marshallers and unmarshallers are implemented there.

Then, as @Goblins and @Pegerto pointed out, you have to call InitializationService.initialize(). I have found this link to be useful for doing a correct initialization when using Dependency Injection https://github.com/apereo/cas/blob/master/support/cas-server-support-saml-core-api/src/main/java/org/apereo/cas/support/saml/OpenSamlConfigBean.java