如何在简单规则中使用变量？

Ricky 发表于常见问题

瑞奇

我习惯使用易用规则JSON descriptor加载规则，而我想在易用规则中使用变量。例如，我有一组规则，其中定义了规则ID，名称，描述，如下所示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\":\"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\\\"]}\"]);"
    ]
  }
]

这里有以下两种可能吗

->使用规则name，description内部动作？

...
[
  {
    "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\\\"]}\"]);"
    ]
  }
]
...

->在动作下使用变量？

...
"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\\\"]}\"]);"
    ]
...

在这里更新我正在初始化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 +
                '}';
    }
}

Mahmoud Ben Hassine

您基本上是在尝试访问条件/操作内的规则信息，或者换句话说，使条件/操作了解规则。您可以使用规则侦听器来执行此操作，该规则侦听器会将规则作为事实放在规则执行之前，然后将其删除。这是一个简单的示例：

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
}

这里是如何使用它：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);
    }
}