Don't json serialize the principal

Since the principal not necessarily is json-searializable we need to avoid this and just pass the wanted properties to thymeleaf fixes codecentric#799

Author: joshiste

spring-boot-admin-server-ui/src/main/java/de/codecentric/boot/admin/server/ui/web/UiController.java

@@ -25,6 +25,9 @@
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.ModelAttribute;
 
+import static java.util.Collections.emptyMap;
+import static java.util.Collections.singletonMap;
+
 @AdminController
 public class UiController {
  private final String adminContextPath;
@@ -48,8 +51,11 @@ public Map<String, Object> getUiSettings() {
  }
 
  @ModelAttribute(value = "user", binding = false)
- public Principal getUiSettings(Principal principal) {
- return principal;
+ public Map<String, Object> getUiSettings(Principal principal) {
+ if (principal != null) {
+ return singletonMap("name", principal.getName());
+ }
+ return emptyMap();
  }
 
  @GetMapping(path = "/", produces = MediaType.TEXT_HTML_VALUE)