[rules-users] question about updating main memory

[Senlin Liang]

Hi all,

I am trying to insert some object, querying them and the retract them.
My question, when I query the inserted objects using defined "query",
it return 0 objects. But when I iterate over all objects in WM, the
objects are returned.

Any information is appreciated!

Files:
===================test.drl====================
package tests;
query "selectQuery"
      p : ClassP()
end
==================end of test.drl================

==================Test.java====================
package tests;

import java.io.*;
import java.io.InputStreamReader;
import org.drools.RuleBase;
import org.drools.RuleBaseFactory;
import org.drools.StatefulSession;
import org.drools.compiler.PackageBuilder;
import org.drools.QueryResult;
import org.drools.QueryResults;
import org.drools.FactHandle;
import java.util.Iterator;

public class Test {
    public static void main (String args[]) {
	try {
	    Reader source = new
InputStreamReader(Test.class.getResourceAsStream("../test.drl"));
	    final PackageBuilder builder = new PackageBuilder();
	    builder.addPackageFromDrl(source);
	    if (builder.hasErrors()) {
		System.out.println(builder.getErrors().toString());
		System.exit(0);
	    }
	    final RuleBase ruleBase = RuleBaseFactory.newRuleBase();
	    ruleBase.addPackage(builder.getPackage());
	    final StatefulSession session = ruleBase.newStatefulSession();

            System.out.println("Inserting objects ...");
	    for (int i = 0; i < 5; i ++) {
		session.insert(new ClassP(1, i));
	    }
	
            System.out.println("Querying objects ...");
	    QueryResults results = session.getQueryResults("selectQuery");
	    System.out.println("ResultSize = " + results.size());
            /***************************************************************************************
             Here, it reports results.size() is 0, and there should be
5 objects in WM right now. It is
             the place I got the question.

             I have no idea whether I am using the "query" correctly.
Anything wrong?
            ***************************************************************************************/
	    for (Iterator it = results.iterator(); it.hasNext(); ) {
		final QueryResult result = (QueryResult) it.next();
		ClassP p = (ClassP) result.get("p");
		System.out.println("p(" + p.getFirst() + ", " + p.getSecond()+")");
	    }

	    System.out.println("Deleting ...");
	    for (Iterator it = session.iterateFactHandles(); it.hasNext(); ) {
		FactHandle factHandle = (FactHandle) it.next();
		ClassP p = (ClassP) session.getObject(factHandle);
		System.out.println("p(" + p.getFirst() + ", " + p.getSecond()+")");
		session.retract(factHandle);
	    }
            /***************************************************************************************
             Here, it prints out: it is deleting p(1, 1), ... p(1, 5).
             It verifies that there are the 5 objects inserted.
            ***************************************************************************************/

	    session.dispose();
	} catch (Exception e) {
	    System.out.println(e);
	    System.exit(0);
	}
    }

    public static class ClassP {
	private int first;
	private int second;
	public ClassP() {}
	public ClassP(int firstIn, int secondIn) {
	    this.first  = firstIn;
	    this.second = secondIn;
	}
	public int getFirst() {
	    return this.first;
	}
	public int getSecond() {
	    return this.second;
	}
    }
}
========================end of Test.java=====================

Thanks a lot,

-- 
Senlin Liang