Daniel E. Markle's Blog

I picked up this K-Line Pennsylvania Railroad MP 15 Diesel Switcher at Ed's Train Repair and Sales. He often has an interesting selection of used trains, and this one caught my eye for the price.

I've always liked the look of trains with weathering and although this one is clearly unintentionally weathered (i.e. rust, dents, and such), with a little bit of strategic spraying it will do its job in an old turnout somewhere on the line; pushing cars out to the mainline for pickup occasionally, most of the time collecting rust while fancy new engines like the one in the background zip by on the mainline.

When working with automatic id's in Grails, sequence generation uses a less than useful default sequence name of hibernate_sequence. Use the following syntax as part of the GORM mapping to set the sequence name to something sane:

static mapping = {
    id generator:sequence,params:[name:'mytable_id_seq']
}

Working on a Spring application using Hibernate recently I encountered the dreaded org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions error. Fixes for this vary widely; it can be caused by problems ranging from bad session handling in your framework configuration, bad cascade settings, incorrect persistence settings, to forgetting initialization of an array stored in a @ManyToOne database relation.

Make sure to check thoroughly for the latter before wasting hours changing the transaction handling, trying various cascade settings, or mucking with persistence annotations.