MySql JPA toplink Auto increment id generation.

To configure JPA entity to make use of auto increment feature of MySql for primary key generation you can make use of IDENTITY strategy ref below code. 

@Entity 
public class Customer { 

        @Id 
        @GeneratedValue(strategy=GenerationType.IDENTITY) 
        private long id;
        .
        .
        .
        public long getId() {
  return id;
 }
}

But problem with this way of generating ids with MySql and JPA combination is when you persist new entity and try to retrieve id assigned to newly persisted entity using getId() method. You get 0 value, because newly generated id for the record is not set with managed entity for that you need to flush after persisting the entity. 

If you don't specify strategy with GeneratedValue annotation, default value will be GenerationType.AUTO. AUTO strategy means your are asking JPA to select appropriate strategy. In most of the cases it is TABLE strategy. 

@Entity 
public class Customer { 

        @Id 
        @GeneratedValue
        private long id;
        .
        .
        .
        public long getId() {
  return id;
 }
}

One can make use of TABLE strategy directly, this way you have more control over configurations.

@Entity 
public class Customer { 

 @Id
 @GeneratedValue(generator = "idgen")
 @TableGenerator(name = "idgen", table = "ID_GEN", pkColumnName = "ID_NAME", valueColumnName = "ID_VAL", pkColumnValue = "CUST_SEQ", allocationSize = 1, initialValue = 0)
        private long id;
        .
        .
        .
        public long getId() {
  return id;
 }
}