10:51 p.m.
Hi,
I am working with Drools to implement a high-profile rules-engine. I have
two rules defined. Clearly, only the first should fire, but both do. Here is
my DRL:
package com.sample
import com.sample.DroolsTest.Request;
rule "ExpensiveCanonShopper0"
when
Request( attributeMap["camera0"] == "canon" &&
attributeMap["price0"] >= 500 )
then
System.out.println("ExpensiveCanonShopper0");
end
rule "ExpensiveCanonShopper1"
when
Request( attributeMap["camera1"] == "canon" &&
attributeMap["price1"] >= 500 )
then
System.out.println("ExpensiveCanonShopper1");
end
And the Java class to execute it:
public class DroolsTest {
@SuppressWarnings({ "rawtypes", "unchecked" })
public static final void main(String[] args) {
try {
//Loading the Rules
System.out.println("Loading rules");
RuleBase ruleBase = readRule();
StatelessSession workingMemory =
ruleBase.newStatelessSession();
System.out.println("Firing rules");
Map map = new HashMap();
map.put("camera0", "canon");
map.put("price0", 600);
Request request = new Request();
request.setAttributeMap(map);
workingMemory.execute(request);
} catch (Throwable t) {
t.printStackTrace();
}
}
/**
* Please note that this is the “low level” rule assembly API.
*/
private static RuleBase readRule() throws Exception {
//read in the source
Reader source = new FileReader(new File("drl",
"Generated.drl"));
//optionally read in the DSL (if you are using it).
//Reader dsl = new InputStreamReader(
DroolsTest.class.getResourceAsStream( “/mylang.dsl” ) );
//Use package builder to build up a rule package.
//An alternative lower level class called “DrlParser” can
also be used…
PackageBuilder builder = new PackageBuilder();
//this wil parse and compile in one step
//NOTE: There are 2 methods here, the one argument one is
for normal DRL.
builder.addPackageFromDrl( source );
if (builder.hasErrors()) {
PackageBuilderErrors errors = builder.getErrors();
throw new RuntimeException("Error adding package to
builder: " + errors.toString());
}
//Use the following instead of above if you are using a DSL:
//builder.addPackageFromDrl( source, dsl );
//get the compiled package (which is serializable)
Package pkg = builder.getPackage();
//add the package to a rulebase (deploy the rule package).
RuleBase ruleBase = RuleBaseFactory.newRuleBase();
ruleBase.addPackage( pkg );
return ruleBase;
}
public static class Request {
private Map attributeMap;
public Map getAttributeMap() {
return attributeMap;
}
public void setAttributeMap(Map attributeMap) {
this.attributeMap = attributeMap;
}
}
}
The output is this, meaning both rules fired:
Loading rules
Firing rules
ExpensiveCanonShopper1
ExpensiveCanonShopper0
I have two questions:
1. Is this a bug, or am I doing something wrong? Only
"ExpensiveCanonShopper0" should fire.
2. I am pretty sure this is somehow related to the fact that I'm using Map
attributes, and not POJO to get "price0" and "camera0". My issue is
that I
won't know the parameters in advance (they are coming in a URL), so I can't
pre-declare them, and thus need something dynamic like a Map. Is this how
Drools is intended to be used? The documentation appears very POJO-centric.
I am using Drools 5.2
Thank you!
-Matt
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