标签:string dep stat errors pac 依赖 mave bye author
规则引擎适用于有复杂多变的规则,如商品满减、积分赠送、考勤规则等
一、引入maven依赖
<dependency> <groupId>org.drools</groupId> <artifactId>drools-core</artifactId> <version>7.13.0.Final</version> </dependency> <dependency> <groupId>org.drools</groupId> <artifactId>drools-compiler</artifactId> <version>7.13.0.Final</version> </dependency>
二、drools有两种执行方式,第一种是基于kmodule.xml、drl配置文件,第二种是动态读取规则
基于kmodule方式
1)创建Fact,drools中的Fact即是java中的普通的bean,用于传递参数
package com.beyond.odc.entity; /** * Fact java bean * @author Hejinsheng */ public class Message { private String message; private String result; private int status; public String getMessage() { return this.message; } public void setMessage(String message) { this.message = message; } public int getStatus() { return this.status; } public void setStatus(int status) { this.status = status; } public String getResult() { return result; } public void setResult(String result) { this.result = result; } }
2)在resources/META-INF下创建kmodule.xml文件,内容如下
<?xml version="1.0" encoding="UTF-8"?> <kmodule xmlns="http://jboss.org/kie/6.0.0/kmodule"> <kbase name="rules" packages="rules"> <ksession name="ksession-rules"/> </kbase> </kmodule>
3)在resources/rules文件夹下创建规则描述文件rules.drl,内容如下
package rules import com.beyond.odc.entity.Message; rule "hello" no-loop true lock-on-active true when $message:Message(status==0) then System.out.println("消息:"+$message.getMessage()); $message.setResult("hello 响应的消息"); update($message) end rule "byebye" no-loop true lock-on-active true when $message:Message(status==1) then System.out.println("消息:"+$message.getMessage()); $message.setResult("byebye 响应的消息"); update($message) end
4)编写测试文件
public static void main(String[] args) { try { KieSession kSession = KieContainerFactory.getKieContainer().newKieSession("ksession-rules"); Message message = new Message(); message.setMessage("hello"); // 对应drl文件中的rule name,表示要执行的规则 message.setStatus(0); // 取message中的某个字段,用户规则文件中的判断是否执行代码块 kSession.insert(message); // 将message作为传递的参数传入drools执行 kSession.fireAllRules(); // 加载规则 System.out.println("从drools中接收到的消息:"+message.getResult()); // drools中如果有参数响应,可以通过字段获取 } catch (Throwable t) { t.printStackTrace(); } }
//KieContainerFactory代码片段 public class KieContainerFactory { private static KieContainer kieContainer; public static KieContainer getKieContainer() { if(kieContainer == null){ // load up the knowledge base KieServices ks = KieServices.Factory.get(); KieContainer kContainer = ks.getKieClasspathContainer(); kieContainer = kContainer; } return kieContainer; } }
5)执行结果,说明代码已经执行到drools文件中,具体的业务逻辑可以在then后的代码块中实现
进来了,消息:hello 从drools中接收到的消息:hello 响应的消息
三、动态方式执行
一般指从数据库或者远程获取的规则描述信息,进行规则执行。动态方式不需要kmodule.xml和drl文件,执行上更加简单
public static void execFromDB(){ KieSession kSession = null; try { // 实际情况从数据库根据code查规则,这里模拟写死 String rule = "package rules\n" + "\n" + "import com.beyond.odc.entity.Message;\n" + "\n" + "rule \"hello\"\n" + " no-loop true\n" + " lock-on-active true\n" + " when\n" + " $message:Message(status==0)\n" + " then\n" + " System.out.println(\"动态执行,消息:\"+$message.getMessage());\n" + " $message.setResult(\"hello 响应的消息\");\n" + " update($message)\n" + "end\n" + "\n" + "rule \"byebye\"\n" + " no-loop true\n" + " lock-on-active true\n" + " when\n" + " $message:Message(status==1)\n" + " then\n" + " System.out.println(\"动态执行,消息:\"+$message.getMessage());\n" + " $message.setResult(\"byebye 响应的消息\");\n" + " update($message)\n" + "end"; KnowledgeBuilder kb = KnowledgeBuilderFactory.newKnowledgeBuilder(); kb.add(ResourceFactory.newByteArrayResource(rule.getBytes("utf-8")), ResourceType.DRL); // 检查规则正确性 KnowledgeBuilderErrors errors = kb.getErrors(); for (KnowledgeBuilderError error : errors) { System.out.println("规则文件正确性有误:{}" + error); } InternalKnowledgeBase kBase = KnowledgeBaseFactory.newKnowledgeBase(); kBase.addPackages(kb.getKnowledgePackages()); // 执行规则 kSession = kBase.newKieSession(); // fact Message fact = new Message(); fact.setMessage("byebye"); fact.setStatus(1); kSession.insert(fact); kSession.fireAllRules(); System.out.println("从drools规则中接收到的消息:"+fact.getResult()); } catch (Exception e) { System.out.println("规则执行异常:{}"+e); } finally { if (null != kSession) kSession.dispose(); } }
执行结果如下:
动态执行,消息:byebye 从drools规则中接收到的消息:byebye 响应的消息
标签:string dep stat errors pac 依赖 mave bye author
原文地址:https://www.cnblogs.com/half-two-feet/p/9876684.html