Grails: Accessing GORM from a background thread - grails

Question

I have been struggling with this error for a week now, and I am seriously losing my mind over this! I have tried multible implementations and work-arounds and hacks and what not, but I just keep stubling into just another exception.
I am using the Executor plugin to run a method asynchroniously:
runAsync{
run(...)
}
The method initially deletes some objects:
page.delete(flush:true)
And then later possibly recreating those objects:
def page = new Page(type : Page.TYPE_TABLE, domain : domainVersion.domain, identifier : tableName)
page.save(flush: true, failOnError: true)
But that fails with the following exception:
Caused by: org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.ramboll.egs.ohs.domain.Domain#1]
The relationship between the Page and Domain is simply implemented by Page having a Domain attribute. No hasMany og belongsTo - as I was discouraged from this in an earlier post due to performance issues.
I think I have tried all thinkable combinations of save, merge, withTransachtion and PersistenceContextInterceptor...
How is this supposed to work? Examples please.
Thanks in advance!

Answer 1

It doesn't appear that working in a new thread is the issue, it looks like a standard validation problem. It's saying that the Page is null, which indicates a validation error since save() returns the instance if it was successful, or null if there's a one or more validation errors. There are a few options:
def page = new Page(type : Page.TYPE_TABLE,
domain: dbUpdate.domainVersion.domain, identifier: tableName)
page.save(flush:true)
if (page.hasErrors()) {
// handle errors
}
else {
def pageVersion = createPageVersion(page, dbUpdate.domainVersion,
con, tableName, dbUpdate.author).save(flush:true)
}
or use failOnError to throw an exception:
def page = new Page(type : Page.TYPE_TABLE, identifier: tableName,
domain: dbUpdate.domainVersion.domain).save(flush:true, failOnError: true)
def pageVersion = createPageVersion(page, dbUpdate.domainVersion,
con, tableName, dbUpdate.author).save(flush:true)