[rules-users] Working memory - database synchronisation approach

[Stephen Masters]

fyi - There may be simpler/cleaner ways of doing it, but if you wish to ensure that you always have access to your Spring context even when you're out roaming on a separate thread, you can get static access to the context like this below. I use it so that I can use Spring to help me get data for Guvnor enums:

/**
* Maintains a static reference to a Spring {@link ApplicationContext}, and a
* static getContext() method, which will initialize the context if necessary.
* 
* @author Stephen Masters
*/
public class GuvnorEnumContext {

private static ApplicationContext ctx = null;

GuvnorEnumContext() {
}

GuvnorEnumContext(ApplicationContext applicationContext) {
ctx = applicationContext;
}

public static ApplicationContext getContext() {
if (ctx == null) {
ctx = new AnnotationConfigApplicationContext(GuvnorEnumConfig.class);
}
return ctx;
}

}

  
/**
* Due to the fashion in which Guvnor enums are invoked, we maintain a
* static reference to the Spring {@link ApplicationContext} in the
* {@link GuvnorEnumContext}. This ensures that the context is only instantiated
* once.
*/
private static MyFinder finder() {
return (MyFinder) GuvnorEnumContext.getContext().getBean("myFinder");
} 



On 28 Mar 2013, at 10:17, Stephen Masters <stephen.masters at me.com> wrote:

> That sounds like a decent design to me. I don't much like having persistence inside the rules.
> 
> The issue you have seems more related to the fact that you're executing the rules in a separate thread than your persistence design. I don't suppose you're actually spawning a thread from inside a JTA transaction in which to run your rules?
> 
> Steve
> 
> 
> On 28 Mar 2013, at 08:46, riri <irina.adam at gmail.com> wrote:
> 
>> Hello everyone,
>> 
>> I am currently working on a Spring, Hibernate, Bitronix project and am
>> trying to integrate Drools functionality. I have a set of JPA Entities that
>> I can manage using Spring Data and Hibernate and I would like to use these
>> entities as facts inside a StatefulKnowledgeSession. As I understand it, I
>> need to have some mechanism of keeping the facts inside the working memory
>> in sync with the database and what I mean by that is:
>> 1. update the facts in working memory when they are changed from outside
>> 2. update the facts in the database when a RHS part of a rule changes
>> properties
>> 
>> This article  http://www.ibm.com/developerworks/java/library/j-drools5/
>> <http://www.ibm.com/developerworks/java/library/j-drools5/>   gives some
>> pointers on how to achieve 1. using AOP but in my case I do not have a
>> global knowledge session to insert, I need to be able to create a knowledge
>> base for each user of the application since each user will need to have his
>> own set of rules independent from other users.
>> 
>> What would be the best practices for achieving the synchronisation?
>> Currently for 1. I am updating the fact manually by retrieving the object
>> and calling update from java code. For 2. I have a
>> WorkingMemoryEventListener that is configured as a Spring @Component with
>> autowired services that can perform CRUD actions on entities and which are
>> called on objectUpdated.
>> 
>> I am new to all these technologies so I do not know if this is a good way to
>> go. I have a unit test where a rule modifies a property and the object is
>> updated in the database but if the Thread with the fireUntilHalt method is
>> not paused, the test finishes and the JTA manager is shut down before the
>> rules can fire and the transaction in the objectUpdated can be executed.
>> 
>> I would be very grateful for any insight from the more experienced users
>> that have come across such requirements before.
>> 
>> Best regards
>> 
>> 
>> 
>> --
>> View this message in context: http://drools.46999.n3.nabble.com/Working-memory-database-synchronisation-approach-tp4023094.html
>> Sent from the Drools: User forum mailing list archive at Nabble.com.
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> 
> 
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