如何在流口水规则引擎中处理列表项中对象的先前值？答案

【问题标题】：How to process Previous value of object in list item in drool rule engine?如何在流口水规则引擎中处理列表项中对象的先前值？
【发布时间】：2017-08-11 09:29:09
【问题描述】：

我希望 Drool 在列表的所有元素中触发规则

这是我的订单类

package com.sample;

import java.util.ArrayList;
import java.util.List;

public class Order {

    public static final int ORDER_AMOUNT_LIMIT = 10;
    public static final int DEFAULT_VALUE=0;

    public int id  ;
    public String name;
    public OrderItem item;
    public String code;
    public List<String> message=new ArrayList<String>();

    public void addmessage(String m) {
        message.add(m);
    }




    public String getCode() {
        return code;
    }
    public void setCode(String code) {
        this.code = code;
    }

    public List<OrderItem> orderItems = new ArrayList<OrderItem>();

    public OrderItem getItem() {
        return item;
    }
    public void setItem(OrderItem item) {
        this.item = item;
    }
    Order(int id,String name){
        this.id = id;
        this.name =  name;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    public void addOrderItem(OrderItem item) {
        orderItems.add(item);
}

}

OrderItem.java

package com.sample;

import java.util.ArrayList;
import java.util.List;

public class OrderItem {

    public static final int TEMP_PRICE = 0; 

    public Order order;
    public int price;
    public String code;
    public List<String> message=new ArrayList();

    public  void addMessage(String msg){
        message.add(msg);
    }


    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    OrderItem(Order order,int price){
        this.order = order;
        this.price = price;
    }

    public Order getOrder() {
        return order;
    }

    public void setOrder(Order order) {
        this.order = order;
    }

    public int getPrice() {
        return price;
    }

    public void setPrice(int price) {
        this.price = price;
    }



}

order.drl

 package com.sample
import com.sample.Order;

rule "order"
when
    $order : Order()
     $total : Double() from accumulate( OrderItem( order == $order, $price : price,code == $order.code,),
                              sum( $price ) )


   eval($total>Order.ORDER_AMOUNT_LIMIT)
then
   System.out.println($total);
   $order.orderItems.get(0).price=0;

   System.out.println("price is "+ $order.orderItems.get(0).getPrice());
end

DroolTest.java

public class DroolsTest {

    public static final void main(String[] args) {
        try {
            // load up the knowledge base
            KieServices ks = KieServices.Factory.get();
            KieContainer kContainer = ks.getKieClasspathContainer();
            KieSession kSession = kContainer.newKieSession("ksession-rules");


            Order order =  new Order(1,"bob");
            order.setCode("test1");

            OrderItem item1 =  new OrderItem(order, 11);
            item1.setCode("test1");
            OrderItem item2 =  new OrderItem(order, 7);
            item2.setCode("test1");

            order.addOrderItem(item1);
            order.addOrderItem( item2 );


            kSession.insert(order);
            kSession.insert(item1);

            kSession.fireAllRules();


            kSession.insert(item2);
            kSession.fireAllRules();            

        } catch (Throwable t) {
            t.printStackTrace();
        }
    }

}

输出

11.0
price is 0

如您所见，then 条件仅执行一次，因为当流口水检查 11 > 10 工作正常并将值设置为 0 但现在当流口水处理第二个列表项时 sum 将返回 0+7 > 10 这是错误的，但我想在第二个列表中触发然后条件 item 因为 11+7 = 19 大于 10 有什么办法可以开火那么两个列表项的条件？有什么办法让我们得到对象的原始值不是来自工作内存？

【问题讨论】：

标签： drools rule business-rules

【解决方案1】：

您添加了一个模式 OrderItem，因此规则将针对超出限制的订单中的每个项目触发。

rule "order"
when
  $order: Order( $code: code )
  accumulate( OrderItem( order == $order, $price: price,
                         code == $code );
              $total: sum( $price );
              $total > Order.ORDER_AMOUNT_LIMIT )
  $item: OrderItem( order == $order, $price: price, code == $code )
then
   System.out.println( $item ); // an order item of a "big" order

end

【讨论】：