Migrate WebFlux sample to Boot

Closes gh-923

samples/boot/webflux/src/main/java/sample/SessionController.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2014-2016 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
+ *
+ *      http://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 sample;
+
+import org.springframework.stereotype.Controller;
+import org.springframework.ui.Model;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.ModelAttribute;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.server.WebSession;
+
+// tag::class[]
+@Controller
+public class SessionController {
+
+	@PostMapping("/session")
+	public String setAttribute(@ModelAttribute SessionAttributeForm sessionAttributeForm, WebSession session) {
+		session.getAttributes().put(sessionAttributeForm.getAttributeName(), sessionAttributeForm.getAttributeValue());
+		return "redirect:/";
+	}
+
+	@GetMapping("/")
+	public String index(Model model, WebSession webSession) {
+		model.addAttribute("webSession", webSession);
+		return "index";
+	}
+
+	private static final long serialVersionUID = 2878267318695777395L;
+}
+// tag::end[]