默认单实例情况下，通过字段循环依赖不会报错，可以互相依赖
@Component
public class BeanA {
private static final Logger logger = LoggerFactory.getLogger(BeanA.class);
@Autowired
private BeanB beanB;
public void print() {
logger.info("hello springboot !");
}
}
@Component
public class BeanB {
private static final Logger logger = LoggerFactory.getLogger(BeanB.class);
@Autowired
private BeanA beanA;
public void print() {
logger.info("hello springboot !");
}
}
构造循环依赖启动时直接报错
异常信息:
The dependencies of some of the beans in the application context form a cycle:
┌─────┐
| beanA defined in file [D:\workspaces\demo\target\classes\com\example\demo\bean2\BeanA.class]
↑ ↓
| beanB defined in file [D:\workspaces\demo\target\classes\com\example\demo\bean2\BeanB.class]
└─────┘
@Component
public class BeanA {
private static final Logger logger = LoggerFactory.getLogger(BeanA.class);
private BeanB beanB;
public BeanA(BeanB beanB) {
this.beanB = beanB;
}
public void print() {
logger.info("hello springboot !");
}
}
@Component
public class BeanB {
private static final Logger logger = LoggerFactory.getLogger(BeanB.class);
private BeanA beanA;
public BeanB(BeanA beanA) {
this.beanA = beanA;
}
public void print() {
logger.info("hello springboot !");
}
}
非单例循环依赖,启动时不会报错,但是获取bean时会报错
异常信息: Requested bean is currently in creation: Is there an unresolvable circular reference?
@Service
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class BeanA {
private static final Logger logger = LoggerFactory.getLogger(BeanA.class);
@Autowired
private BeanB beanB;
public void print() {
logger.info("hello springboot !");
}
}
@Service
@Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
public class BeanB {
private static final Logger logger = LoggerFactory.getLogger(BeanB.class);
@Autowired
private BeanA beanA;
public void print() {
logger.info("hello springboot !");
}
}
测试代码
@SpringBootApplication
public class DemoApplication {
private static final Logger logger = LoggerFactory.getLogger(DemoApplication.class);
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(DemoApplication.class, args);
BeanA bean = context.getBean(BeanA.class);
bean.print();
}
}