3.4. Function - JBoss RULES 4.0.0.11754MR2 manual 英文版使用指南文档
Functions are a way to put semantic code in your rule source, as opposed to in normal java classes. They can't do anything more then what you can do with helper classes (in fact, the compiler generates the helper class for you behind the scenes, isn't that helpful). The main advantage of using functions in a rule is that you can keep the logic all in one place, and you can change the functions as needed (this can be a good and bad thing). Functions are most useful for invoking actions on the consequence ("then") part of a rule, especially if that particular action is used over and over (perhaps with only differing parameters for each rule - for example the contents of an email message).
A typical function declaration looks like:
function String calcSomething(String arg) {
return "hola !";
}
Note that the "function" keyword is used, even though its not really part of java. Parameters to the function are just like a normal method (and you don't have to have parameters if they are not needed). Return type is just like a normal method. To call the function from within a rule (in a consequence, or perhaps an eval, simply use the function name, and toss in the parameters - just like a method call).
An alternative to a function, could be to use a static method in a helper class: Foo.doSomething(), or perhaps pass in an instance of a helper class/service as a named global (see the section on globals): foo.soSomething() (where foo is a named global variable).