extends the functionality of oauth in Stirling PDF

src/main/java/stirling/software/SPDF/config/security/InitialSecuritySetup.java

@@ -7,6 +7,8 @@ import java.nio.file.Paths;
 import java.util.List;
 import java.util.UUID;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
 
@@ -21,6 +23,8 @@ public class InitialSecuritySetup {
 
     @Autowired ApplicationProperties applicationProperties;
 
+    private static final Logger logger = LoggerFactory.getLogger(InitialSecuritySetup.class);
+
     @PostConstruct
     public void init() {
         if (!userService.hasUsers()) {
@@ -29,6 +33,20 @@ public class InitialSecuritySetup {
                     applicationProperties.getSecurity().getInitialLogin().getUsername();
             String initialPassword =
                     applicationProperties.getSecurity().getInitialLogin().getPassword();
+            try {
+                // https://github.com/Stirling-Tools/Stirling-PDF/issues/976
+                userService.isUsernameValidWithReturn(initialUsername);
+            } catch (IllegalArgumentException e) {
+                Path pathToFile = Paths.get("configs/settings.yml");
+                try {
+                    if (Files.exists(pathToFile)) {
+                        Files.delete(pathToFile);
+                    }
+                } catch (IOException ex) {
+                    logger.info(ex.getMessage());
+                }
+                throw e;
+            }
             if (initialUsername != null && initialPassword != null) {
                 userService.saveUser(initialUsername, initialPassword, Role.ADMIN.getRoleId());
             } else {