Resource Server Opaque Token Sample

Issue: gh-5200

samples/boot/oauth2resourceserver-opaque/src/main/java/sample/OAuth2ResourceServerController.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2002-2019 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.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+/**
+ * @author Josh Cummings
+ */
+@RestController
+public class OAuth2ResourceServerController {
+
+	@GetMapping("/")
+	public String index(@AuthenticationPrincipal(expression="['sub']") String subject) {
+		return String.format("Hello, %s!", subject);
+	}
+
+	@GetMapping("/message")
+	public String message() {
+		return "secret message";
+	}
+}