Error decoding incoming SAML message

Hello,

I am trying to implement single sign on across three of my webapps using the spring SAML extension. But I am implementing the sample app given before implementing the SAML extension on my own apps. However I get this error in my browser after I sign in to the sample app:

HTTP Status 401 - Authentication Failed: Error decoding incoming SAML message

type Status report

message Authentication Failed: Error decoding incoming SAML message

description This request requires HTTP authentication.

Apache Tomcat/7.0.41


and the tomcat log says:

INFO: Server startup in 7861 ms
- No default metadata configured, generating with default values, please pre-con figure metadata for production use
- Created default metadata for system with entityID: https://localhost:8443/spri ng-security-saml2-sample/saml/metadata/alias/defaultAlias
- AuthNRequest;SUCCESS;127.0.0.1
- PKIX path construction failed for untrusted credential: [subjectName='CN=servername.local' |credential entityID='http://servername.local/adfs/services/trust']: unable to find valid certification path to requested target



I am using this guide to implement single sign on:
http://static.springsource.org/sprin...idp-guide.html

with this sample application
https://github.com/SpringSource/spri...r/saml2-sample

Using an ADFS Windows 2012 server standard