如何在Java中动态构建Drools规则？

Question

How to build Drools rules in Java dynamically instead of providing static drl file?

I have a set of matching rules defined in xml that I need to parse and be able to reload it in runtime. Is there any way to build Drools rules dynamically? Couldn't find it in the docs.

Answer 1

I agree with former answers and comments that rules are ment to be the "static" part. When rules are created dynamically on demand, the usage of a rules engine is questionable. However, there are cases where rules are not provided in form / format that drools can handle out of the box. In such cases programmatical creation of rules during the initialization phase is needed.

These things said, here is how you can add a rule (given as a String) to drools.

public void addRule(String myRuleStatement, String myPackage, RuleBase myRuleBase ) {
    PackageBuilder packageBuilder = new PackageBuilder(new Package(myPackage));
    packageBuilder.addPackgeFromDrl( new StringReader( myRuleStatement ) );
    myRuleBase.addPackage ( packageBuilder.getPackage() );
}

Answer 2

我同意Romain的评论-如果您具有某种声明形式的规则-您可以直接从中生成代码-除非这些规则中隐含了更高阶的逻辑（不太可能找到），或者您可能想做一个时间从XML迁移到规则语言。