如何访问在drools中作为事实插入的String对象

declare MyFact
    myString: String
end

rule "My Rule"
when
    // 规则条件
then
    MyFact fact = new MyFact();
    fact.setMyString("Hello, World!");
    insert(fact);
end

// 创建KieServices实例
KieServices kieServices = KieServices.Factory.get();

// 加载规则文件
KieContainer kieContainer = kieServices.getKieClasspathContainer();

// 创建KieSession实例
KieSession kieSession = kieContainer.newKieSession();

// 执行规则
kieSession.fireAllRules();

// 获取插入的String对象
QueryResults results = kieSession.getQueryResults("getMyString");
for (QueryResultsRow row : results) {
    MyFact fact = (MyFact) row.get("$fact");
    String myString = fact.getMyString();
    System.out.println(myString);
}

query "getMyString"
    $fact: MyFact()
end