title: Annotations from javax.validation.constraints not working
body: <p>What configuration is needed to use annotations from <code>javax.validation.constraints</code> like <code>@Size</code>, <code>@NotNull</code>, etc.? Here's my code:</p>
  
  <pre><code>import javax.validation.constraints.NotNull;
  import javax.validation.constraints.Size;
  
  public class Person {
        @NotNull
        private String id;
  
        @Size(max = 3)
        private String name;
  
        private int age;
  
        public Person(String id, String name, int age) {
          this.id = id;
          this.name = name;
          this.age = age;
        }
  }
  </code></pre>
  
  <p>When I try to use it in another class, validation doesn't work (i.e. the object is created without error):</p>
  
  <pre><code>Person P = new Person(null, "Richard3", 8229));
  </code></pre>
  
  <p>Why doesn't this apply constraints for <code>id</code> and <code>name</code>? What else do I need to do?</p>