protected MessageHandler buildCheckMandatoryIssuer() throws ComponentInitializationException {
        val mandatoryIssuer = new CheckMandatoryIssuer();
        mandatoryIssuer.setIssuerLookupStrategy(new IssuerFunction());
        mandatoryIssuer.initialize();
        return mandatoryIssuer;
    }
<p>buildCheckMandatoryIssuer.</p>

@return a {@link MessageHandler} object
@throws ComponentInitializationException if any.
pac4j-saml/src/main/java/org/pac4j/saml/sso/artifact/DefaultSOAPPipelineFactory.java