循环依赖 - 流程图

Spring 默认是支持循环依赖（并且可以关闭）的，但是必须满足两个条件

• 必须基于 setter 方法注入
• 互斥引用的双方**不能都是 prototype 的 ```java @Service public class OrderService { @Autowired private UserService userService; public OrderService() {

    System.out.println("OrderService Constructor");

  } }

@Service public class UserService { @Autowired private OrderService orderService; public UserService() { System.out.println(“UserService Constructor”); } }

public class App { public static void main(String[] args) { AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(); ac.register(AppConfig.class); ac.refresh();

    System.out.println(ac.getBean(UserService.class));
}

}

// 打印结果 UserService Constructor OrderService Constructor org.wesoft.spring.cycle.bean.UserService@3224f60b

<a name="wIBvn"></a>
### 关闭循环依赖
```java
public class App {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext();
        ac.register(AppConfig.class);
        // 关闭循环依赖
        DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) ac.getBeanFactory();
        beanFactory.setAllowCircularReferences(false);
        ac.refresh();
        System.out.println(ac.getBean(UserService.class));
    }
}

循环依赖流程图

一直不太想写循环依赖逻辑，因为牵扯的知识点非常非常多，并不是网上很多说循环依赖的那么简单的几百个字，画张图吧，先走黑色线，再走蓝色线，再走橘黄色线，再走黄色线，再走墨兰色线