Drools在运行时从数据库中获取事实

Question

我需要一点Drools eval和变量赋值的帮助.

rule "check that no previously submitted requests exist"
when
    $user : UserFormField( name == 'employeeId', value != null )
    $repository : Repository(  )
    $activeRequests : List( ) from $repository.findActiveRequestsByEmployee( $user.getValue() ) # call to repository
    eval( $activeRequests.size() > 0 )
then
    System.err.println(' You have active requests: ' + ((Request)$activeRequests.get(0)).getTitle);
    insert(Boolean.TRUE);
end

在此规则中,我尝试访问存储库并获取当前用户的活动请求.规则编译和执行,没有任何例外或警告.在调试模式下,可以看到存储库返回非空列表,我希望看到控制台消息"您有活动请求",但这不会发生.我认为问题出在这一行

$activeRequests : List( ) from $repository.findActiveRequestsByEmployee( $user.getValue() )

因为这条规则很好

rule "check that no previously submitted requests exist"
when
    $user : UserFormField( name == 'employeeId', value != null )
    $repository : Repository(  )
    eval( $repository.findActiveRequestsByEmployee($user.getValue()).size() > 0 )
then
    System.err.println(' You have active requests !' );
    insert(Boolean.TRUE);
end

有人能指出我如何解决这个问题吗？

谢谢!

Answer 1

我帮助找到了解决方案.我应该使用from collect表达式来简单地from将事实捆绑到集合中:

$activeRequests : ArrayList() from collect ( Request() from $repository.findActiveRequestsByEmployee( $user.getValue() ) )