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Showing posts from September, 2012

Predicates Java Pattern to save Database Queries

The apache commons CollectionUtils has a collection of very interesting methods to allow using Ruby style collection filtering, rejecting,collecting injecting ...

I found the select method quite useful to avoid multiple DB Queries with a DB similar predicate and syntactically clean.

Problem: I wish to append a List/Collection to my Bean based on some predicate (orgId="mcool").

Use of Predicates:

Basic Example:BeanPropertyValueEqualsPredicate  predicate = new BeanPropertyValueEqualsPredicate("orgId", value);

BeanPropertyValueEqualsPredicate predicate = new BeanPropertyValueEqualsPredicate("orgId", value); Collection<Organisation> organisationCool =, predicate); allOrganisations above was fetched with a single sql select.

bean.setOrganisationsList(organisationCool );

Caution:  Needless to say but typically small datasets and only for cases where in memory selection is beneficial.

More about the Ruby …