编辑“︁Spring引入通知（Introduction Advice）”︁（章节）

== 实际案例 ==
考虑一个电商系统中的订单服务，我们想在不修改原始类的情况下为其添加审计功能：

<syntaxhighlight lang="java">
// 原始服务类
public class OrderServiceImpl implements OrderService {
    public void createOrder(Order order) {
        // 业务逻辑
    }
}

// 审计接口
public interface Auditable {
    void setAuditLogger(AuditLogger logger);
    void logAuditEvent(String event);
}

// 审计实现
public class DefaultAuditable implements Auditable {
    private AuditLogger auditLogger;
    
    public void setAuditLogger(AuditLogger logger) {
        this.auditLogger = logger;
    }
    
    public void logAuditEvent(String event) {
        if(auditLogger != null) {
            auditLogger.log(event);
        }
    }
}

// 引入切面
@Aspect
public class AuditingIntroductionAspect {
    @DeclareParents(value="com.example.service.OrderServiceImpl",
                   defaultImpl=DefaultAuditable.class)
    public static Auditable auditable;
}

// 使用示例
OrderService orderService = applicationContext.getBean(OrderService.class);
((Auditable)orderService).setAuditLogger(auditLogger);
((Auditable)orderService).logAuditEvent("Order created");
</syntaxhighlight>