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Because the SP's handlers have to know which application is receiving a request, each application has to be assigned a unique "base location", which is called a handlerURL. By convention, this base location is "/Shibboleth.sso".
Often, each application spans a particular virtual host, and the base location is simply "/Shibboleth.sso" on that vhost. In more advanced cases, an application might live inside a subset of a virtual host's document tree. In that case, the base location has to be inside that document tree (e.g., "/path/Shibboleth.sso").
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http(s):// + hostname + [:port] +
handlerURL+Location
If you require to access the handler URL from your code (for example to trigger a login), the "Shib-Handler" attribute is availble set to the full path above (minus the Location) for a programatic way to access the path set in the configuration.
In turn, these endpoint locations are usually supplied to partner sites in Metadata. When they don't match the metadata, various errors will result.
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