I am not changing anything for velocity engine. When execute below code from Pac4jHTTPPostEncoder class:

this.getVelocityEngine().mergeTemplate(this.getVelocityTemplateId(), "UTF-8", velocityContext, out);

Error:

MESSAGE:    .pac4j.saml.exceptions.SAMLException: Error encoding saml message
SERVLET:    default
CAUSED BY:  .pac4j.saml.exceptions.SAMLException: Error encoding saml message
CAUSED BY:  .opensaml.messaging.encoder.MessageEncodingException: Error creating output document
CAUSED BY:  .apache.velocity.exception.ResourceNotFoundException: Unable to find resource '/templates/saml2-post-binding.vm'
Caused by:
.pac4j.saml.exceptions.SAMLException: Error encoding saml message
    at .pac4j.saml.profile.impl.AbstractSAML2MessageSender.sendMessage(AbstractSAML2MessageSender.java:100)
    at .pac4j.saml.sso.impl.SAML2WebSSOProfileHandler.send(SAML2WebSSOProfileHandler.java:30)
    at .pac4j.saml.sso.impl.SAML2WebSSOProfileHandler.send(SAML2WebSSOProfileHandler.java:16)
    at com.g1.dcg.server.security.web.saml.SpectrumSAML2RedirectActionBuilder.getRedirectionAction(SpectrumSAML2RedirectActionBuilder.java:82)
    at .pac4j.core.client.IndirectClient.getRedirectionAction(IndirectClient.java:111)
    at .pac4j.core.engine.DefaultSecurityLogic.redirectToIdentityProvider(DefaultSecurityLogic.java:237)
    at .pac4j.core.engine.DefaultSecurityLogic.perform(DefaultSecurityLogic.java:150)
    at .pac4j.jee.filter.SecurityFilter.internalFilter(SecurityFilter.java:82)
    at .pac4j.jee.config.AbstractConfigFilter.doFilter(AbstractConfigFilter.java:72)
    at .springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
    at .springframework.security.web.header.HeaderWriterFilter.doHeadersAfter(HeaderWriterFilter.java:90)
    at .springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:75)
    at .springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
    at .springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)
    at com.g1.dcg.server.security.web.filters.SecurityContextPersistenceFilter.internalFilter(SecurityContextPersistenceFilter.java:72)
    at com.g1.dcg.server.security.web.filters.AbstractSecurityFilter.doFilter(AbstractSecurityFilter.java:25)
    at .springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:374)

I am not getting where should I look for file /templates/saml2-post-binding.vm