Add saml2-login java-configuration sample

Issue gh-10

servlet/java-configuration/saml2/login/src/main/java/example/IndexController.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2002-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package example;
+
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.saml2.provider.service.authentication.Saml2AuthenticatedPrincipal;
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.GetMapping;
+
+/**
+ * Controller for "/".
+ *
+ * @author Rob WInch
+ */
+@Controller
+public class IndexController {
+
+	@GetMapping("/")
+	public String index(Model model, @AuthenticationPrincipal Saml2AuthenticatedPrincipal principal) {
+		String emailAddress = principal.getFirstAttribute("emailAddress");
+		model.addAttribute("emailAddress", emailAddress);
+		model.addAttribute("userAttributes", principal.getAttributes());
+		return "index";
+	}
+
+}