GUACAMOLE-1364: Extract common SSO resource for IdP redirect.

extensions/guacamole-auth-sso/modules/guacamole-auth-sso-saml/src/main/java/org/apache/guacamole/auth/saml/AuthenticationProviderService.java

@@ -95,16 +95,20 @@ public class AuthenticationProviderService implements SSOAuthenticationProviderS
 
         // Redirect to SAML IdP if no SAML identity is associated with the
         // Guacamole authentication request
-        URI authUri = saml.createRequest();
         throw new GuacamoleInvalidCredentialsException("Redirecting to SAML IdP.",
                 new CredentialsInfo(Arrays.asList(new Field[] {
-                    new RedirectField(AUTH_SESSION_QUERY_PARAM, authUri,
+                    new RedirectField(AUTH_SESSION_QUERY_PARAM, getLoginURI(),
                             new TranslatableMessage("LOGIN.INFO_IDP_REDIRECT_PENDING"))
                 }))
         );
 
     }
 
+    @Override
+    public URI getLoginURI() throws GuacamoleException {
+        return saml.createRequest();
+    }
+
     @Override
     public void shutdown() {
         sessionManager.shutdown();

extensions/guacamole-auth-sso/modules/guacamole-auth-sso-saml/src/main/java/org/apache/guacamole/auth/saml/acs/AssertionConsumerServiceResource.java

@@ -39,7 +39,7 @@ import org.slf4j.LoggerFactory;
  * endpoint. SAML identity providers will issue an HTTP POST to this endpoint
  * asserting the user's identity when the user has successfully authenticated.
  */
-public class AssertionConsumerServiceResource implements SSOResource {
+public class AssertionConsumerServiceResource extends SSOResource {
 
     /**
      * Logger for this class.
@@ -64,11 +64,6 @@ public class AssertionConsumerServiceResource implements SSOResource {
     @Inject
     private SAMLService saml;
 
-    @Override
-    public Response redirectToIdentityProvider() throws GuacamoleException {
-        return Response.seeOther(saml.createRequest()).build();
-    }
-
     /**
      * Processes the SAML response submitted by the SAML IdP via an HTTP POST.
      * If SSO has been successful, the user is redirected back to Guacamole to