Question

我有一个模型对象帐户

package com.drool.model;

import java.util.Date;

public class Acccount {

    private int id;
    private int balance;
    private Date transDate;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getBalance() {
        return balance;
    }
    public void setBalance(int balance) {
        this.balance = balance;
    }
    public Date getTransDate() {
        return transDate;
    }
    public void setTransDate(Date transDate) {
        this.transDate = transDate;
    }



}

DroolsRule

import com.drool.model.Acccount

rule "accountTransaction"
when
$first : Acccount()
$second : Acccount( this != $first, transDate==$first.transDate )
then
System.out.println("second Accounbt had latest transaction");
end

测试应用程序代码：

KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
kbuilder.add(ResourceFactory.newClassPathResource("HelloWorld.drl"), ResourceType.DRL);
KnowledgeBase kbase = kbuilder.newKnowledgeBase();
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
Acccount account = new Acccount();
account.setBalance(1000000);
account.setId(123);
account.setTransDate(new Date());
Acccount account1 = new Acccount();
account1.setBalance(200);
account1.setId(1234);
account1.setTransDate(new Date());
ksession.insert(account);
ksession.insert(account1);
ksession.fireAllRules();

输出：

second Accounbt had latest transaction
second Accounbt had latest transaction

我是drools的新手，当我运行上面的示例时。结果打印两次，理想情况下只打印一次。如果我的规则是正确的，请告诉我？

Answer 1

像这样的一对约束：

$first : Acccount()
$second : Acccount( this != $first, transDate==$first.transDate )

如果它完全发射，

必然会发射两次。由于同一日期的两个Acccount事实，事实A被绑定到$first，因此事实B被匹配并绑定到$second。但是A和B的对称性并没有被约束所打破，因此同样的事情再次发生，A和B交换角色。

要避免这种情况，请使用具有排序关系的唯一属性，大概是id：

$first : Acccount( $id1: id )
$second : Acccount( id > $id1, transDate==$first.transDate )

Answer 2

如果您想使用“帐户（名称=”格式）比较同一班级的两个实例，您会怎么做。

比较Drools中相同对象的两个实例

2 个答案: