How to get a Fact creating BRL in Guvnor and querying Drools Server

Question

I'm stuck with BRL rules in Guvnor.. I'm trying to execute rules from my application using Drools Server (this solution because in production I can use more server and maybe improve performance.. Not sure about this as it's the first time that in my company we are using Drools)..

So basically the rule is .. Given an object Route setting the property "selectedOutboundJourney" that I uploaded in guvnor in a jar, I'd like to get another object with the property "selectedReturnJourney" set.. (but Is it possible to get the same object??) Actually I get a Route object where the selectedReturnJourney is null.

I'm not sure if using BRL is a good solution given the troubles that I'm having.. It seems easy to use for non technical people that may want to change the rules or creating new ones.

Anyway..

This is the BRL that I created in Guvnor:

rule "Selected Return for Dover - Calais"
   dialect "mvel"
    when
        Route( selectedOutboundJourney == "DOCA" )
    then
        Route fact0 = new Route();
        fact0.setSelectedReturnJourney( "CADO" );
        insertLogical( fact0 );
        end

This is the code I'm using:

final List<Command> commands = new ArrayList<Command>();
final Command insertObjectCommand = CommandFactory.newInsert(input, RESULT, true, "default");
final Command getObjectCommand = CommandFactory.newGetObjects();
final Command fireAllRulesCommand = CommandFactory.newFireAllRules();
commands.add(insertObjectCommand);
commands.add(getObjectCommand);
commands.add(fireAllRulesCommand);

final ExecutionResults executionResults = droolsHttpClient.callDroolsServer(commands);
return executionResults.getValue(RESULT);

The class DroolsHttpClient is:

public ExecutionResults callDroolsServer(final List<Command> commands) throws  DroolsException
{
    PostMethod postMethod = null;
    try
    {
        final HttpClient httpClient = new HttpClient();
        final String droolsServerHost = Config.getString(PoferriesrulesengineConstants.DROOLS_SERVER_HOST, "");
        final int droolsServerPort = Config.getInt(PoferriesrulesengineConstants.DROOLS_SERVER_PORT, 0);
        httpClient.getHostConfiguration().setHost(droolsServerHost, droolsServerPort);

        final String droolsServerUrl = Config.getString(PoferriesrulesengineConstants.DROOLS_SERVER_URL, "");
        postMethod = new PostMethod(droolsServerUrl);

        final BatchExecutionCommand command = CommandFactory.newBatchExecution(commands, PoferriesrulesengineConstants.DROOLS_SESSION);
        final XStream xStreamMarshaller = BatchExecutionHelper.newXStreamMarshaller();
        final String xmlCommand = xStreamMarshaller.toXML(command);

        final StringRequestEntity request = new StringRequestEntity(xmlCommand, MediaType.TEXT_PLAIN_VALUE, CharEncoding.UTF_8);
        postMethod.setRequestEntity(request);

        httpClient.executeMethod(postMethod);
        if (postMethod.getStatusCode() != 200)
        {
            throw new RuntimeException("Drools Communication Error, code: " + postMethod.getStatusCode());
        }
        final String response = postMethod.getResponseBodyAsString();

        final ExecutionResults executionResults = (ExecutionResults) xStreamMarshaller.fromXML(response);
        return executionResults;
    }
    catch (final Exception e)
    {
        throw new DroolsException(e.getMessage());
    }
    finally
    {
        postMethod.releaseConnection();
    }
}

If I use a DRL like below it words perfectly without using the getObjectCommand:

rule "Selected Return Routes for Dover Calais"

    when
    r : Route(selectedOutboundJourney == "DOCA")
then
    r.setSelectedReturnJourney("CADO")

end

Can anyone help me out, please?

Answer 1

Assuming you only have one fact in your Knowledge Session at the start, after the execution of the following rule

rule "Selected Return for Dover - Calais"
dialect "mvel"
when
    Route( selectedOutboundJourney == "DOCA" )
then
    Route fact0 = new Route()
    fact0.setSelectedReturnJourney( "CADO" )
    insert( fact0 )
end

you will have two Route facts in your session, since you just have inserted the second one.

Route: selectedOutboundJourney = "DOCA", selectedReturnJourney=null
Route: selectedOutboundJourney = null, selectedReturnJourney="DACO"

If you want to modify the original fact use the following rule:

rule "Selected Return Routes for Dover Calais"
when
   $r : Route(selectedOutboundJourney == "DOCA")
then
   modify ($r) {
     selectedReturnJourney = "CADO"
   }
end