java – 我应该在这种情况下使用Drools吗？

通过规则引擎运行大量书籍将会变得昂贵.特别是因为您不会向用户显示所有结果：每页只有10-50个.想到的一个想法是使用规则引擎构建一组查询条件. (我实际上不会这样做 – 见下文)

这是我想到的：

rule "Only two books for networking"
when
  Student($checkedOutBooks : checkedOutBooks),Book(subjects contains "networking",$book1 : id) from $checkedOutBooks,id != $book1) from $checkedOutBooks
then
  criteria.add("subject is not 'networking'",PRIORITY.LOW);
end

rule "Books allowed for course"
when
  $course : Course($textbooks : textbooks),Student(enrolledCourses contains $course)

  Book($book : id) from $textbooks,then
  criteria.add("book_id = " + $book,PRIORITY.HIGH);
end

但我实际上不会这样做！

这是我如何改变问题：
不向用户显示书籍是一种糟糕的经历.用户可能想要仔细阅读这些书籍,看看下一次要下载哪些书籍.显示书籍,但不允许结帐受限制的书籍.这样,每个用户一次只能运行1-50本书来执行规则.这将是相当zippy.上述规则将成为：

rule "Allowed for course"
   activation-group "Only one rule is fired"
   salience 10000
when
  // This book is about to be displayed on the page,hence inserted into working memory
  $book : Book(),$course : Course(textbooks contains $book),Student(enrolledCourses contains $course),then
  //Do nothing,allow the book
end

rule "Only two books for networking"
   activation-group "Only one rule is fired"
   salience 100
when
  Student($checkedOutBooks : checkedOutBooks),id != $book1) from $checkedOutBooks,// This book is about to be displayed on the page,hence inserted into working memory.
  $book : Book(subjects contains "networking")
then
  disallowedForCheckout.put($book,"Cannot have more than two networking books");
end

我正在使用激活组来确保只有一个规则被触发,并且显着地确保它们按照我想要的顺序触发.

最后,保持规则缓存. Drools允许 – 并建议 – 您只将规则加载到知识库中,然后从中创建会话.知识库昂贵,会话便宜.