Red Hat Summit 红帽全球峰会支持控制台（Console）开发人员开始试用联系人

此内容没有您所选择的语言版本。

3.2. JBoss Rules Theory

3.2.1. Methods in JBoss Rules
复制链接

Methods are different to rules. They are called directly and are used to pass specific instances. A single call results in a single execution.
Report a bug

3.2.2. Method Example
复制链接

A method looks like this: 
public void helloWorld(Person person) {
    if ( person.getName().equals( "Chuck" ) ) {
        System.out.println( "Hello Chuck" );
    }
}
Report a bug

3.2.3. Rule Example
复制链接

A rule looks like this: 
rule "Hello World"
    when
        Person( name == "Chuck" )
    then
        System.out.println( "Hello Chuck" );
end
Report a bug

3.2.4. Cross-Products
复制链接

When two or more sets of data are combined, the result is called a cross-product.
Report a bug

3.2.5. Cross-Product Constraining
复制链接

Procedure 3.6. Task

  • To prevent a rule from outputting a huge amount of cross-products, you should constrain the cross-products themselves. Do this using the variable constraint seen below: 
    rule
when
    $room : Room()
    $sprinkler : Sprinkler( room == $room )
then
    System.out.println( "room:" + $room.getName() +
                        " sprinkler:" + $sprinkler.getRoom().getName() );
end
    The following output will be displayed: 
    room:office sprinkler:office
room:kitchen sprinkler:kitchen
room:livingroom sprinkler:livingroom
room:bedroom sprinkler:bedroom
Result

Only four rows are outputted with the correct sprinkler for each room. Without this variable, every row in the Room table would have been joined with every row in the Sprinkler table resulting in many lines of output.

Report a bug

3.2.6. The Inference Engine
复制链接

The inference engine is the part of the JBoss Rules engine which matches production facts and data to rules. It will then perform actions based on what it infers from the information. A production rules system's inference engine is stateful and is responsible for truth maintenance.
Report a bug

3.2.7. Inference Example
复制链接

In this example, a Person fact with an age field and a rule that provides age policy control is used. Inference is used to determine if a Person is an adult or a minor, then act on the result: 
rule "Infer Adult"
when
  $p : Person( age >= 18 )
then
  insert( new IsAdult( $p ) )
end
In the above snippet, every Person who is 18 or over will have an instance of IsAdult inserted for them. This fact is special in that it is known as a relation. We can use this inferred relation in any rule: 
$p : Person()
IsAdult( person == $p )
Report a bug
Red Hat logoGithubredditYoutubeTwitter

学习

尝试、购买和销售

社区

关于红帽文档

通过我们的产品和服务，以及可以信赖的内容，帮助红帽用户创新并实现他们的目标。 了解我们当前的更新.

让开源更具包容性

红帽致力于替换我们的代码、文档和 Web 属性中存在问题的语言。欲了解更多详情，请参阅红帽博客.

關於紅帽

我们提供强化的解决方案，使企业能够更轻松地跨平台和环境（从核心数据中心到网络边缘）工作。

Theme

© 2026 Red Hat返回顶部