Note that there is a subtle distinction between (a) the creation of database objects in the database, and (b) the instantiation of Java model objects that represent database objects (i.e., JObjects). These two events do not necessarily always occur at the same time. Methods that are annotated with @OnCreate are invoked only for event (a). In particular, Java model objects are frequently instantiated to represent database objects that already exist in the database. Also, it's possible for a Java model object to be instantiated when no corresponding database object exists in the database (e.g., via JTransaction.get(org.jsimpledb.core.ObjId)).

As a consequence, for any database fields that require default initialization, this initialization should be performed not in a Java constructor but rather in an @OnCreate-annotated method.

For example, instead of this:

  @JSimpleClass
  public abstract class Event {

      protected Event() {
          this.setCreateTime(new Date());
      }

      public abstract Date getCreateTime();
      public abstract void setCreateTime(Date createTime);

      ...
 

  @JSimpleClass
  public abstract class Event {

      protected Event() {
      }

      @OnCreate
      private void init() {
          this.setCreateTime(new Date());
      }

      public abstract Date getCreateTime();
      public abstract void setCreateTime(Date createTime);

      ...
 

Notifications are delivered in the same thread that created the object, immediately after the object is created.

The annotated method must be an instance method (i.e., not static), return void, and take zero parameters. It may have any level of access, including private.