[rules-users] Getting data from a relational database

[Stephen Masters]

As a general rule, query the database in the Java code, and insert the objects retrieved as facts in the session. Then your LHS just needs to match on those facts. Either that or populate a global.

If you have a stateless session, then you could get away with facts with getter methods which return collections and which are actually calling the database. However, it's horribly inefficient, more error prone (for one thing, you can't put a try-catch in your LHS) and less readable than performing the database queries up front in your Java code.

fyi - On my last contract, the main reason I was able to achieve a ~1000x speed gain was removing database queries from the LHS and instead performing them up front and inserting the results as facts via the Java API.

Steve


On 30 Aug 2013, at 18:47, rtanikella <rtanikella at gmail.com> wrote:

> Hi,
> 
> I am using Drools Server 5.4.0.Final as a web application deployed on JBoss
> AS 7.1.1.Final, and Guvnor 5.4.0.Final for authoring/managing the business
> rules.
> 
> I need to get data from a relational database (and eventually any other
> external system) into the WHEN clause of any rule in the Guvnor, and, if
> needed, be able to insert that data into the working memory via the THEN
> clause. What is the best approach in achieving this? If there are any
> examples or samples, please point them out.
> 
> Thanks,
> Ramgopal Tanikella
> 
> 
> 
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> View this message in context: http://drools.46999.n3.nabble.com/Getting-data-from-a-relational-database-tp4025736.html
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