måndag, februari 06, 2006

Combining TopLink with Oracle Business Rules

This sample will show you how you retrieve some objects by using TopLink and then use Oracle Business Rules to do some selection upon these objects. I am not using neither a file based nor a WebDAV based rule repository for this sample, instead I create the ruleset on the fly.

Suppose you have a table, PERSON, that has the following structure:


and this is mapped to a Person object which has corresponding fields and accessors. I will also assume that you have setup a TopLink mapping between the table and the object.

Now, we first need to retrieve the objects from the DB, assuming we are working with a 2-tier here, we do this as follows:

SessionManager sessionManager = SessionManager.getManager();
Session session = sessionManager.getSession("default");
Vector v = session.readAllObjects(Person.class);

This will read all persons in the database and put them into a Vector. Now, we have a vector, v, that holds our persons. The next step is to initiate the RuleSession, as mentioned before, this is done on the fly with one simple rule:

RuleSession rs = new RuleSession();
String rset =
"ruleset main {" +
" import ruleexample1.bo.Person;" +
" rule blueEyeFemaleWithIncomeOver40000 {" +
" if (fact Person p && p.getEye_color().equals(\"Blue\") && p.getSex().equals(\"F\") && p.getIncome()>40000 ) {" +
" println(p.getName() + \" is a female with blue eyes and an income over 400000.\");" +
" }" +
" }" +

this rule will fire for females with blue eyes and has an income over 40000. Once done, we can assign the persons as facts, this is done by:

for (int i=0;i<v.size();i++) {
rs.callFunctionWithArgument( "assert", (Person)v.elementAt(i) );

once the facts are in place, we can run this by calling:

rs.callFunction( "run" );

That's it! This will print out a list of objects that matches the conditions set out in the rule set.

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