diff --git a/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/AuthDto.java b/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/AuthDto.java
index fb7ec13..d1c85ff 100644
--- a/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/AuthDto.java
+++ b/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/AuthDto.java
@@ -1,18 +1,18 @@
 package dev.earlspilner.auth.dto;
 
 import io.swagger.v3.oas.annotations.media.Schema;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 
 /**
  * @author Alexander Dudkin
  */
 @Schema(description = "Authentication request data")
 public record AuthDto(
-        @NotNull
+        @NotBlank
         @Schema(description = "User's username", example = "thisdudkin", requiredMode = Schema.RequiredMode.REQUIRED)
         String username,
 
-        @NotNull
+        @NotBlank
         @Schema(description = "User's password", example = "password", requiredMode = Schema.RequiredMode.REQUIRED)
         String password
 ) { }
diff --git a/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/Tokens.java b/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/Tokens.java
index 00a55f3..179cebb 100644
--- a/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/Tokens.java
+++ b/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/Tokens.java
@@ -1,18 +1,18 @@
 package dev.earlspilner.auth.dto;
 
 import io.swagger.v3.oas.annotations.media.Schema;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 
 /**
  * @author Alexander Dudkin
  */
 @Schema(description = "Access and refresh tokens")
 public record Tokens(
-        @NotNull
+        @NotBlank
         @Schema(description = "Access token", example = "eyJhbGciOiJIUzI1...", requiredMode = Schema.RequiredMode.REQUIRED)
         String accessToken,
 
-        @NotNull
+        @NotBlank
         @Schema(description = "Refresh token", example = "dXNlci1yZWZyZXNoLXRva2Vu..", requiredMode = Schema.RequiredMode.REQUIRED)
         String refreshToken
 ) { }
diff --git a/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/UserDto.java b/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/UserDto.java
index 7ed8a6a..4615a4d 100644
--- a/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/UserDto.java
+++ b/library-api-authentication-server/src/main/java/dev/earlspilner/auth/dto/UserDto.java
@@ -2,7 +2,7 @@
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import jakarta.validation.constraints.Email;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 
 import java.util.List;
 
@@ -14,10 +14,10 @@
 @JsonInclude(NON_NULL)
 public record UserDto(
         Integer id,
-        @NotNull String name,
-        @NotNull String username,
-        @Email @NotNull String email,
-        @NotNull String password,
+        @NotBlank String name,
+        @NotBlank String username,
+        @Email @NotBlank String email,
+        @NotBlank String password,
         String createdUtc,
         String updatedUtc,
         List<UserRole> roles
diff --git a/library-api-books-service/src/main/java/dev/earlspilner/books/dto/BookDto.java b/library-api-books-service/src/main/java/dev/earlspilner/books/dto/BookDto.java
index 40813c4..01f06f1 100644
--- a/library-api-books-service/src/main/java/dev/earlspilner/books/dto/BookDto.java
+++ b/library-api-books-service/src/main/java/dev/earlspilner/books/dto/BookDto.java
@@ -1,7 +1,7 @@
 package dev.earlspilner.books.dto;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 import org.hibernate.validator.constraints.ISBN;
 
 import static com.fasterxml.jackson.annotation.JsonInclude.Include.NON_NULL;
@@ -12,11 +12,11 @@
 @JsonInclude(NON_NULL)
 public record BookDto(
         Integer id,
-        @ISBN @NotNull String isbn,
-        @NotNull String title,
-        @NotNull String genre,
-        @NotNull String description,
-        @NotNull String author,
+        @ISBN @NotBlank String isbn,
+        @NotBlank String title,
+        @NotBlank String genre,
+        @NotBlank String description,
+        @NotBlank String author,
         Boolean isAvailable,
         String appearedUtc
 ) { }
diff --git a/library-api-books-service/src/main/java/dev/earlspilner/books/dto/UserDto.java b/library-api-books-service/src/main/java/dev/earlspilner/books/dto/UserDto.java
index 77d9329..6ba6ec5 100644
--- a/library-api-books-service/src/main/java/dev/earlspilner/books/dto/UserDto.java
+++ b/library-api-books-service/src/main/java/dev/earlspilner/books/dto/UserDto.java
@@ -2,7 +2,7 @@
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import jakarta.validation.constraints.Email;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 
 import java.util.List;
 
@@ -14,10 +14,10 @@
 @JsonInclude(NON_NULL)
 public record UserDto(
         Integer id,
-        @NotNull String name,
-        @NotNull String username,
-        @Email @NotNull String email,
-        @NotNull String password,
+        @NotBlank String name,
+        @NotBlank String username,
+        @Email @NotBlank String email,
+        @NotBlank String password,
         String createdUtc,
         String updatedUtc,
         List<UserRole> roles
diff --git a/library-api-library-service/src/main/java/dev/earlspilner/library/dto/UserDto.java b/library-api-library-service/src/main/java/dev/earlspilner/library/dto/UserDto.java
index eee7fb3..a468ff5 100644
--- a/library-api-library-service/src/main/java/dev/earlspilner/library/dto/UserDto.java
+++ b/library-api-library-service/src/main/java/dev/earlspilner/library/dto/UserDto.java
@@ -2,7 +2,7 @@
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import jakarta.validation.constraints.Email;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 
 import java.util.List;
 
@@ -14,10 +14,10 @@
 @JsonInclude(NON_NULL)
 public record UserDto(
         Integer id,
-        @NotNull String name,
-        @NotNull String username,
-        @Email @NotNull String email,
-        @NotNull String password,
+        @NotBlank String name,
+        @NotBlank String username,
+        @Email @NotBlank String email,
+        @NotBlank String password,
         String createdUtc,
         String updatedUtc,
         List<UserRole> roles
diff --git a/library-api-loan-service/src/main/java/dev/earlspilner/loans/dto/UserDto.java b/library-api-loan-service/src/main/java/dev/earlspilner/loans/dto/UserDto.java
index e6023c4..b8b1835 100644
--- a/library-api-loan-service/src/main/java/dev/earlspilner/loans/dto/UserDto.java
+++ b/library-api-loan-service/src/main/java/dev/earlspilner/loans/dto/UserDto.java
@@ -2,7 +2,7 @@
 
 import com.fasterxml.jackson.annotation.JsonInclude;
 import jakarta.validation.constraints.Email;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 
 import java.util.List;
 
@@ -14,10 +14,10 @@
 @JsonInclude(NON_NULL)
 public record UserDto(
         Integer id,
-        @NotNull String name,
-        @NotNull String username,
-        @Email @NotNull String email,
-        @NotNull String password,
+        @NotBlank String name,
+        @NotBlank String username,
+        @Email @NotBlank String email,
+        @NotBlank String password,
         String createdUtc,
         String updatedUtc,
         List<UserRole> roles
diff --git a/library-api-users-service/src/main/java/dev/earlspilner/users/dto/UserDto.java b/library-api-users-service/src/main/java/dev/earlspilner/users/dto/UserDto.java
index a573ba8..c8e7f2d 100644
--- a/library-api-users-service/src/main/java/dev/earlspilner/users/dto/UserDto.java
+++ b/library-api-users-service/src/main/java/dev/earlspilner/users/dto/UserDto.java
@@ -3,7 +3,7 @@
 import com.fasterxml.jackson.annotation.JsonInclude;
 import dev.earlspilner.users.model.UserRole;
 import jakarta.validation.constraints.Email;
-import jakarta.validation.constraints.NotNull;
+import jakarta.validation.constraints.NotBlank;
 
 import java.util.List;
 
@@ -15,10 +15,10 @@
 @JsonInclude(NON_NULL)
 public record UserDto(
         Integer id,
-        @NotNull String name,
-        @NotNull String username,
-        @Email @NotNull String email,
-        @NotNull String password,
+        @NotBlank String name,
+        @NotBlank String username,
+        @Email @NotBlank String email,
+        @NotBlank String password,
         String createdUtc,
         String updatedUtc,
         List<UserRole> roles