如何在简单规则中使用变量?

How to use variables in easy rules?

我正在使用 JSON descriptor 来加载使用 easy-rules 的规则,我想在简单规则 actions 中使用变量。例如,我有一组规则,我在其中定义规则 ID、名称、描述,如下所示

[
  {
    "id": 1,
    "name": "Task using Oracle DB",
    "description": "Updated comments to update connector",
    "priority": 1,
    "condition": "user.getTaskData().getTargetConnectorType().contains(\"Oracle\") || user.getTaskData().getSourceConnectorType().contains(\"Oracle\")",
    "actions": [
      "user.setRuleDetail([\"impacted_feature\":\"Task using Oracle DB\", \"desc\": \"Updated comments to update connector\", \"impact\":\"low\", \"count\":\"Using \"+user.getTaskDetail().getConnBucketData().get(\"Oracle\")+\" connector type\",\"id\":1, \"extra_detail\":\"{\\"impacted_connectors\\":[\\"Oracle\\"]}\"]);"
    ]
  }
]

下面两种可能吗

-> 使用规则 name, description inside actions?

...
[
  {
    "id": 1,
    "name": "Task using Oracle DB",
    "description": "Updated comments to update connector",
    "priority": 1,
    "condition": "user.getTaskData().getTargetConnectorType().contains(\"Oracle\") || user.getTaskData().getSourceConnectorType().contains(\"Oracle\")",
    "actions": [
      "user.setRuleDetail([\"impacted_feature\":\"+name+\", \"desc\": \"+description+\", \"impact\":\"low\", \"count\":\"Using \"+user.getTaskDetail().getConnBucketData().get(\"Oracle\")+\" connector type\",\"id\":1, \"extra_detail\":\"{\\"impacted_connectors\\":[\\"Oracle\\"]}\"]);"
    ]
  }
]
...

-> 在操作下使用变量?

...
"actions": [
        "def name = \"Task using Oracle DB\"",
        "def desc = \"Updated comments to update connector\"",
        "def connector = \"Oracle\"",           
      "user.setRuleDetail([\"impacted_feature\":\"+name+\", \"desc\": \"+desc+\", \"impact\":\"low\", \"count\":\"Using \"+user.getTaskDetail().getConnBucketData().get(\"Oracle\")+\" connector type\",\"id\":1, \"extra_detail\":\"{\\"impacted_connectors\\":[\\"Oracle\\"]}\"]);"
    ]
...

更新 这里我在初始化MVELRuleFactory

def computeRules(UserData userData) {
    try {
        Facts facts = new Facts()
        facts.put("user", userData)

        MVELRuleFactory ruleFactory = new MVELRuleFactory(new JsonRuleDefinitionReader())
        Rules rules = ruleFactory.createRules(new FileReader("conf/rules.json"))

        //create a default rules engine and fire rules on known facts
        RulesEngine rulesEngine = new DefaultRulesEngine()
        rulesEngine.fire(rules, facts)
    } catch(FileNotFoundException fnfe) {
        _errorLogger.error("Error in #computeRules {}", fnfe)
    } catch(Exception e) {
        _errorLogger.error("Error in #computeRules {}", e)
    }
    return userData.getRuleDetail()
}

//UserData POJO

@CompileStatic
class UserData {
    String orgKey
    TaskData taskData
    List<Map> ruleDetail

    UserData(String orgKey, TaskData taskData) {
        this.orgKey = orgKey
        this.taskData = taskData
    }

    String getOrgKey() {
        return orgKey
    }

    void setOrgKey(String orgKey) {
        this.orgKey = orgKey
    }

    TaskData getTaskData() {
        return taskData
    }

    void setTaskData(TaskData taskData) {
        this.taskData = taskData
    }

    List<Map> getRuleDetail() {
        return ruleDetail
    }

    void setRuleDetail(Map ruleData) {
        if (this.ruleDetail == null)
            this.ruleDetail = []
        this.ruleDetail.add(ruleData)
    }

    @Override
    public String toString() {
        return "UserData{" +
                "orgKey='" + orgKey + '\'' +
                ", taskData=" + taskData +
                ", ruleDetail=" + ruleDetail +
                '}';
    }
}

总结一下,没有也有!

要了解如何,您必须了解只要变量以 Fact 形式存在或以某种方式存在于 MVEL 上下文中,就可以解析。

这里有详细的解答-

Use rule name, description inside actions?

没有。您不能在 Action 中使用 Rulenamedescription。要在规则中使用外部变量,您必须将它们添加为事实。如果您想要这种能力,请使用 drools,它 feature richheavy framework.

Use a variable under actions?

这你可以做到,但不是你所拥有的方式。 defMVEL里面有特殊的含义。所以要使用变量,你可以做这些事情中的任何一个-

  1. 将变量定义为单独的操作项:

    "actions": [
       "name=\"....\"",
       "description=\"....\"",
       "user.setRuleDetail([\"impacted_feature\": name, \"desc\": description, \"impact\": \"low\", \"count\":\"Using \"+user.getTaskDetail().getConnBucketData().get(\"Oracle\")+\" connector type\",\"id\":1, \"extra_detail\":\"{\\"impacted_connectors\\":[\\"Oracle\\"]}\"]);"
    ]
    
  2. 添加行内变量:

    "actions": [
       "name=\"....\";description=\"....\";user.setRuleDetail([\"impacted_feature\": name, \"desc\": description, \"impact\": \"low\", \"count\":\"Using \"+user.getTaskDetail().getConnBucketData().get(\"Oracle\")+\" connector type\",\"id\":1, \"extra_detail\":\"{\\"impacted_connectors\\":[\\"Oracle\\"]}\"]);"
    ]
    

    注意在动作中使用它们时不需要额外的 quotes

希望对您有所帮助!

您基本上是在尝试访问 condition/action 内的规则信息,或者换句话说,让 condition/action 了解该规则。您可以使用规则侦听器来做到这一点,该侦听器在规则执行之前将规则作为事实并在之后将其删除。这是一个简单的例子:

public class MyListener implements RuleListener {
    @Override
    public void beforeExecute(Rule rule, Facts facts) {
        facts.put("rule", rule);
    }

    @Override
    public void onSuccess(Rule rule, Facts facts) {
        facts.remove("rule");
    }

    @Override
    public void onFailure(Rule rule, Facts facts, Exception exception) {
        facts.remove("rule");
    }

    // implement other methods if needed
}

下面是如何使用它:给定以下规则描述文件 rule-aware-action.json:

[
  {
    "name": "rule aware action",
    "description": "a rule where the action is aware of the rule",
    "condition": "true",
    "actions": [
      "System.out.println(rule.name);"
    ]
  }
]

以下示例打印 rule aware action:

import java.io.FileReader;

import org.jeasy.rules.api.Facts;
import org.jeasy.rules.api.Rule;
import org.jeasy.rules.api.RuleListener;
import org.jeasy.rules.api.Rules;
import org.jeasy.rules.core.DefaultRulesEngine;
import org.jeasy.rules.mvel.MVELRuleFactory;
import org.jeasy.rules.support.reader.JsonRuleDefinitionReader;

public class RuleAwareActionExample {

    public static void main(String[] args) throws Exception {
        MVELRuleFactory mvelRuleFactory = new MVELRuleFactory(new JsonRuleDefinitionReader());
        Rules rules = mvelRuleFactory.createRules(new FileReader("rule-aware-action.json"));
        DefaultRulesEngine rulesEngine = new DefaultRulesEngine();
        rulesEngine.registerRuleListener(new MyListener());
        Facts facts = new Facts();
        rulesEngine.fire(rules, facts);
    }
}

这意味着操作能够访问它所属的规则的名称。该示例展示了如何使操作了解其规则,但它也应该适用于条件。