一、系统架构设计

基于Drools+Spring Boot的动态规则引擎，实现业务规则与代码解耦，支持热更新和版本管理

二、核心功能实现

1. 规则定义与加载

public class RuleLoader {
    private final KieServices kieServices = KieServices.Factory.get();
    
    public KieContainer loadRulesFromString(String ruleContent) {
        KieFileSystem kfs = kieServices.newKieFileSystem();
        kfs.write("src/main/resources/rules.drl", 
            kieServices.getResources()
                .newReaderResource(new StringReader(ruleContent)));
        
        KieBuilder kieBuilder = kieServices.newKieBuilder(kfs).buildAll();
        Results results = kieBuilder.getResults();
        if (results.hasMessages(Message.Level.ERROR)) {
            throw new RuntimeException("规则编译错误: " + results.getMessages());
        }
        
        return kieServices.newKieContainer(
            kieServices.getRepository().getDefaultReleaseId());
    }
    
    public KieContainer loadRulesFromDatabase() {
        List rules = ruleRepository.findActiveRules();
        String ruleContent = rules.stream()
            .map(Rule::getContent)
            .collect(Collectors.joining("n"));
        
        return loadRulesFromString(ruleContent);
    }
}

2. 规则执行引擎

@Service
public class RuleEngineService {
    private final AtomicReference kieContainerRef = 
        new AtomicReference();
    
    @PostConstruct
    public void init() {
        reloadRules();
    }
    
    public void reloadRules() {
        KieContainer newContainer = ruleLoader.loadRulesFromDatabase();
        KieContainer oldContainer = kieContainerRef.getAndSet(newContainer);
        if (oldContainer != null) {
            oldContainer.dispose();
        }
    }
    
    public  T executeRules(T fact) {
        KieSession kieSession = kieContainerRef.get().newKieSession();
        try {
            kieSession.insert(fact);
            kieSession.fireAllRules();
            return fact;
        } finally {
            kieSession.dispose();
        }
    }
    
    public  List executeRules(Collection facts) {
        return facts.stream()
            .map(this::executeRules)
            .collect(Collectors.toList());
    }
}

3. 规则版本管理

@Entity
public class Rule {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private String ruleKey;
    private String name;
    private String content;
    private Integer version;
    private Boolean active;
    private LocalDateTime createTime;
    
    // Getters and Setters
}

public interface RuleRepository extends JpaRepository {
    @Query("SELECT r FROM Rule r WHERE r.active = true ORDER BY r.ruleKey, r.version DESC")
    List findActiveRules();
    
    @Modifying
    @Query("UPDATE Rule r SET r.active = false WHERE r.ruleKey = :ruleKey")
    void deactivateAllVersions(@Param("ruleKey") String ruleKey);
}

三、高级功能实现

1. 规则调试工具

@RestController
@RequestMapping("/api/rules")
public class RuleDebugController {
    
    @PostMapping("/debug")
    public RuleDebugResult debugRule(@RequestBody RuleDebugRequest request) {
        KieSession kieSession = ruleEngineService.createDebugSession();
        try {
            kieSession.setGlobal("debugResult", request.getDebugResult());
            kieSession.insert(request.getFact());
            kieSession.fireAllRules();
            return request.getDebugResult();
        } finally {
            kieSession.dispose();
        }
    }
    
    @GetMapping("/activations")
    public List getRuleActivations(@RequestBody Object fact) {
        KieSession kieSession = ruleEngineService.createDebugSession();
        List activations = new ArrayList();
        
        kieSession.addEventListener(new AgendaEventListener() {
            public void matchCreated(MatchCreatedEvent event) {
                activations.add(new RuleActivation(
                    event.getMatch().getRule().getName(),
                    event.getMatch().getObjects()
                ));
            }
            // 其他事件方法...
        });
        
        try {
            kieSession.insert(fact);
            kieSession.fireAllRules();
            return activations;
        } finally {
            kieSession.dispose();
        }
    }
}

2. 性能优化方案

• 规则分组：按业务领域拆分规则文件
• 预编译：启动时预加载常用规则
• 会话池：复用KieSession减少创建开销
• 监听器优化：选择性注册事件监听器

四、实战案例演示

1. 电商促销规则应用

// 规则文件示例
rule "VIP用户折扣"
    when
        $order: Order(customer.vip == true)
    then
        $order.setDiscount(0.2);
end

rule "满减活动"
    when
        $order: Order(totalAmount >= 500)
    then
        $order.setDiscount($order.getDiscount() + 0.1);
end

// Java调用示例
public Order applyPromotions(Order order) {
    return ruleEngineService.executeRules(order);
}

// 批量处理
public List applyPromotions(List orders) {
    return ruleEngineService.executeRules(orders);
}

2. 性能测试数据

测试场景：1000个订单应用20条规则
首次加载时间：1.2s
规则执行时间：45ms
内存占用峰值：350MB
吞吐量：850请求/秒