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Grails - Querying complex associations

Criteria class allows performing complex searches on grails objects. There are number of shortcut methods for performing queries but these methods have limitations in terms of number of conditions used in "where clauses". Traditional sql "joins" are not possible as shown in some of the Grails "Finder" methods shown below.

Sample 1:
def list = AccountTransaction.findAllByCompanyCodeAndVoucherDateBetween(branch, fromDate, toDate, params)

Sample 2:
def list = AccountTransaction.findAllByCompanyCodeAndVoucherDateGreaterThanEquals(branch, fromDate, params)

Sample 3:
def list = AccountTransaction.findAllByCompanyCodeAndTransGroup(branch, group, params)

"params" contains attributes related to sorting, paging etc. It is very easy to use finder methods but when you want to filter objects by more conditions we need to look for alternatives.

For understanding the relationships used in this sample, I listed the grails domain classes.

class TransactionType{
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