use Validator for @NotNull

documentation/src/main/asciidoc/introduction/Entities.adoc

@@ -554,6 +554,12 @@ Note that primitively-typed attributes are inferred `NOT NULL` by default.
 String middleName; // may be null
 ----
 
+[TIP]
+====
+An even better solution is to use the `@NotNull` annotation from Bean Validation.
+Just add Hibernate Validator to your project build.
+====
+
 .Should I use `optional=false` or `nullable=false` in JPA?
 ****
 There are two ways to mark a mapped column `not null` in JPA:
@@ -577,7 +583,8 @@ Note that:
 - `optional=false` implies `nullable=false`, but
 - `nullable=false` _does not_ imply `optional=false`.
 
-Therefore, we recommend `@Basic(optional=false)` in preference to `@Column(nullable=false)` in most circumstances.
+Therefore, we prefer `@Basic(optional=false)` to `@Column(nullable=false)`.
+But the `@NotNull` annotation from Bean Validation is even nicer.
 ****
 
 [[enums]]

documentation/src/main/asciidoc/introduction/Hibernate_Introduction.adoc

@@ -227,6 +227,10 @@ dependencies {
     // the GOAT ORM
     implementation 'org.hibernate.orm:hibernate-core:6.2.2.Final'
 
+    // Hibernate Validator
+    implementation 'org.hibernate.validator:hibernate-validator:8.0.0.Final'
+    implementation 'org.glassfish:jakarta.el:4.0.2'
+
     // Agroal connection pool
     implementation 'org.hibernate.orm:hibernate-agroal:6.2.2.Final'
     implementation 'io.agroal:agroal-pool:2.1'
@@ -270,16 +274,16 @@ We begin with our _entity class_:
 ----
 package org.hibernate.example;
 
-import jakarta.persistence.Basic;
 import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
+import jakarta.validation.constraints.NotNull;
 
 @Entity
 class Book {
     @Id
     String isbn;
 
-    @Basic(optional = false)
+    @NotNull
     String title;
 
     Book() {}