JBoss Drools 规则引擎示例程序

package com.sample;
import java.io.InputStreamReader;
import java.io.Reader;
import org.drools.RuleBase;
import org.drools.RuleBaseFactory;
import org.drools.WorkingMemory;
import org.drools.compiler.PackageBuilder;
import org.drools.rule.Package;
public class DroolsTest {

public static final void main(String[] args) {

try {
RuleBase ruleBase = readRule();
WorkingMemory workingMemory = ruleBase.newStatefulSession();
Message message = new Message();
message.setMessage("Hello World");
message.setStatus(Message.HELLO);
workingMemory.insert(message);
workingMemory.fireAllRules();
} catch (Throwable t) {
t.printStackTrace();
}
}
private static RuleBase readRule() throws Exception {

Reader source = new InputStreamReader(DroolsTest.class.getResourceAsStream("./Sample.drl"));
PackageBuilder builder = new PackageBuilder();
builder.addPackageFromDrl(source);
Package pkg = builder.getPackage();
RuleBase ruleBase = RuleBaseFactory.newRuleBase();
ruleBase.addPackage(pkg);
return ruleBase;
}
public static class Message {

public static final int HELLO = 0;
public static final int GOODBYE = 1;
public static final int GAME_OVER = 2;
private String message;
private int status;
public String getMessage() {
return this.message;
}
public void setMessage(String message) {
this.message = message;
}
public int getStatus() {
return this.status;
}
public void setStatus(int status) {
this.status = status;
}
}
}

package com.sample
import com.sample.DroolsTest.Message;
rule "Hello World"
when
m : Message( status == Message.HELLO, message : message )
then
System.out.println( message );
m.setMessage( "Goodbye cruel world" );
m.setStatus( Message.GOODBYE );
update( m );
end
rule "GoodBye"
no-loop true
when
m : Message( status == Message.GOODBYE, message : message )
then
System.out.println( message );
m.setStatus(Message.GAME_OVER);
m.setMessage("game over now!");
update( m );
end
rule "game over"
when
m : Message( status == Message.GAME_OVER)
then
System.out.println( m.getMessage() );
end