如何编辑和更新 Drools 规则文件？

Question

我的项目使用了 drools expert means (DRL) 文件。在规则文件中，如果用户想删除和更新规则，应该怎么办？

规则文件：

package com.sample;

import com.sample.Tuplebean;
import com.sample.DroolsBolt;

dialect "mvel"

rule "SafetyAlert-Critical"
when
    t:Tuplebean(t.getSmoke() == true && t.getSmoke_density() == true && t.getTemperature() > 25.0)
then
    DroolsBolt.insertToAlertLog("alert generated");
end

比如用户想把温度的值改成30.0

Answer 1

在我的应用程序中，我遇到了同样的问题，我通过休闲方式解决了这些问题，我正在维护所有规则文件数据库。

我将所有规则文件保存在 tables 中，并且我正在根据 IMEI 编号加载每个规则文件（在我的例子中，我为一个适配器生成一个规则，即具有唯一 IMEI 编号的适配器） .

在下面的代码中，首先从数据库加载规则文件并将该字符串转换为资源，因为资源工厂只接受资源作为构造函数参数。并将其存储到 ksession 中并触发规则。

对于编辑和删除操作，我在数据库中制作了一个标志，如果该标志再次为真，则将规则文件更新到数据库table。如果为假，则加载相同的旧规则文件。

在这里您生成规则文件并保存到数据库 table 如果标志为真，您再次 re-generate 规则文件。

public void generateDrrols(String macAddress) throws SQLException, ClassNotFoundException, IOException{
        logger.error("++++Generate drools file started++++");
        Class.forName("org.postgresql.Driver");
        Connection conn = DriverManager.getConnection("jdbc:postgresql://10.0.0.5:5432/iotdb",
                    "postgres", "track@123");

        //String sql="SELECT alert_playload FROM iot.alert_configuration WHERE drools_boolean=true and alert_configuration_id=94 && 95";
         String sql = ""
              + "select drools_condtion , iot.alert_configuration.alert_status , iot.alert_configuration.websocket_key , device_id , iot.alert_configuration.device_configuration_id , "
              + "email , iot.alert_configuration.mac_address , phone , sensor_id , iot.alert_configuration.sensor_configuration_id , alert_configuration_id , site_id , "
              + "startdatetime , enddatetime , exludedays , timetoexclude , log_update_time ,iot.sensor_configuration.sensor_name "
              + "from iot.alert_configuration "
              + "join iot.sensor_configuration on iot.sensor_configuration.sensor_configuration_id=iot.alert_configuration.sensor_configuration_id "
              + "where iot.alert_configuration.mac_address=? and soft_delete_flag=false";

         PreparedStatement prepareStatement = conn.prepareStatement(sql);
         prepareStatement.setString(1, macAddress);
         ResultSet rs = prepareStatement.executeQuery();
        //ResultSet rs = sta.executeQuery(sql);

        final ResultSetGenerator converter = new ResultSetGenerator();
        InputStream in = getClass().getResourceAsStream("/alert.drt"); 
        final String drl = converter.compile(rs, in);
        System.out.println(drl);
        rs.close();
        KnowledgeBuilder kbuilder =
              KnowledgeBuilderFactory.newKnowledgeBuilder();
        kbuilder.add(ResourceFactory.newByteArrayResource(drl.getBytes()),
                   ResourceType.DRL);
        KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
        kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());
        StatefulKnowledgeSession kSession = 
        kbase.newStatefulKnowledgeSession();
        logger.error("++++Reading rule file ie., rule.drl started++++");

        logger.error("++++Making drool table status false++++");
        String sql2="update iot.drool_rules set drool_rules=? where mac_address=?";
        PreparedStatement prepareStatement2 = conn.prepareStatement(sql2);
        prepareStatement2.setString(1, drl.toString());
        prepareStatement2.setString(2, macAddress);
        boolean execute2 = prepareStatement2.execute();
        String sql1="update iot.alert_configuration set storm_drool_status=false where mac_address=?";
        //Statement createStatement = conn.createStatement();
        PreparedStatement prepareStatement3 = conn.prepareStatement(sql1);
        prepareStatement3.setString(1, macAddress);
        boolean execute = prepareStatement3.execute();

    }

在这里，您从数据库中加载规则文件并触发所有规则。

KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder();
    try{
        String sql="select drool_rules from iot.drool_rules where mac_address=?";
        PreparedStatement prepareStatement = connectPostgres.prepareStatement(hql);
        prepareStatement.setString(1, topicId);
        ResultSet executeQuery1 = prepareStatement.executeQuery();
        String rules=null;
        while(executeQuery1.next()){
            rules=executeQuery1.getString(1);
        }
        String i=null;
        String replace = rules.replace('"', '\"');
        System.out.println(replace);
        Reader reader=(Reader)new StringReader(replace);
        Resource myResource = ResourceFactory.newReaderResource(reader);
        kbuilder.add(myResource, ResourceType.DRL);
    }
    catch(Exception e)
    {
        e.printStackTrace();
    }
        KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
        kbase.addKnowledgePackages( kbuilder.getKnowledgePackages() );
        ksession = kbase.newStatefulKnowledgeSession();

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