[UNDERTOW-2660] Add RoutingHandler example RoutingServer

Author: anamitraupadhyay

examples/src/main/java/io/undertow/examples/routingserver/RoutingServer.java

@@ -0,0 +1,75 @@
+/*
+ * JBoss, Home of Professional Open Source.
+ * Copyright 2025 Red Hat, Inc., and individual contributors
+ * as indicated by the @author tags.
+ *
+ * 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 io.undertow.examples.routingserver;
+
+import io.undertow.Handlers;
+import io.undertow.Undertow;
+import io.undertow.examples.UndertowExample;
+import io.undertow.server.HttpServerExchange;
+import io.undertow.server.RoutingHandler;
+import io.undertow.util.Headers;
+
+import java.nio.charset.StandardCharsets;
+
+/**
+ * An example of how to use the RoutingHandler to dispatch
+ * to different handlers based on the request method (GET, POST, etc.).
+ *
+ * Demonstrates:
+ * - GET /greet
+ * - POST /greet
+ * - Fallback 404 handler
+ *
+ * Author: anamitraupadhyay
+ */
+@UndertowExample("Routing Handler")
+public class RoutingServer {
+
+    public static void main(final String[] args) {
+        RoutingHandler handler = Handlers.routing()
+                .get("/greet", RoutingServer::handleGetRequest)
+                .post("/greet", RoutingServer::handlePostRequest)
+                .get("/*", exchange -> {
+                    exchange.setStatusCode(404);
+                    exchange.getResponseHeaders().put(Headers.CONTENT_TYPE, "text/plain");
+                    exchange.getResponseSender().send("Page Not Found");
+                });
+
+        Undertow server = Undertow.builder()
+                .addHttpListener(8080, "localhost")
+                .setHandler(handler)
+                .build();
+        server.start();
+    }
+
+    private static void handleGetRequest(HttpServerExchange exchange) {
+        String name = "World";
+        exchange.getResponseHeaders().put(Headers.CONTENT_TYPE, "text/plain");
+        exchange.getResponseSender().send("Hello " + name);
+    }
+
+    private static void handlePostRequest(HttpServerExchange exchange) {
+        exchange.getRequestReceiver().receiveFullString(
+                (HttpServerExchange exc, String body) -> {
+                    exc.getResponseHeaders().put(Headers.CONTENT_TYPE, "text/plain");
+                    exc.getResponseSender().send("Hello " + body);
+                },
+                StandardCharsets.UTF_8
+        );
+    }
+}