I checked this again against Version 1.5 of groovy.
Testcase still failed

Improvements have been made which should fix this problem but the test suite is fairly minimal in this area - please test as much as you can.

The test script InsertNullIntoDBTest.groovy does not fail running under GroovyGroovy 1.5.3 JVM : 1.6.0_03-b05 (Ubuntu Linux).

However, the following slight variation does fail:

db.execute "INSERT INTO COUNTRY (country,currency) VALUES (?,?)",[it.key,it.value]

with the following output:

US USD
DE EUR
GB null
Caught: org.postgresql.util.PSQLException: No value specified for parameter 2.
at InsertNullIntoDBTest$_run_closure1.doCall(InsertNullIntoDBTest.groovy:19)
at InsertNullIntoDBTest.run(InsertNullIntoDBTest.groovy:17)
at InsertNullIntoDBTest.main(InsertNullIntoDBTest.groovy)

You might need to provide more info. This script:

Map countryMap = ['US' : 'USD', 'DE' : 'EUR', 'GB' : null]

countryMap.each{
    println it.key + " " + it.value
    db.execute "INSERT INTO COUNTRY (country,currency) VALUES (?,?)", [it.key, it.value]
}

works for me on 1.5.4 using hsql.

This seems related to GROOVY-2585 perhaps it was only working on HSQL and would fail on other databases. Leaving this issue closed but follow the other issue for further progress.

close off release 1.5.4