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This document is targeted towards developers writing a custom portlet that will support Shibboleth Delegated Authentication. For an "out of the box" solution look at using the Web Proxy Portlet with Shibboleth Delegated SAML Authentication
The delegated-saml-authentication project is a library that handles most of the complexities around delegated Shibboleth authentication for the portlet developer. The library provides a specially configured HttpClient from Commomns Http-Components 4.x that can be used to make requests to a remote service that will automatically use delegated authentication.
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