How to get active user's UserDetails with AuthenticationPrincipal (#14398)

spring-security-modules/spring-security-web-rest-custom/src/main/java/com/baeldung/web/controller/SecurityController4.java

@@ -0,0 +1,16 @@
+package com.baeldung.web.controller;
+
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class SecurityController4 {
+
+    @GetMapping("/user")
+    public String getUser(@AuthenticationPrincipal UserDetails userDetails) {
+        return "User Details: " + userDetails.getUsername();
+    }
+
+}