16.0 Spring扩展点应用
Spring扩展点在微服务组件中的应用
前提:
- 掌握Spring主线流程源码
- 掌握Spring Boot主线流程源码
- 熟悉Spring Cloud&Spring Cloud Alibaba中间件核心功能源码
一、Spring扩展点梳理
-
BeanFactoryPostProcessor
-
- BeanDefinitionRegistryPostProcessor
-
BeanPostProcessor
-
- InstantiationAwareBeanPostProcessor
- AbstractAutoProxyCreator
-
@Import
-
- ImportBeanDefinitionRegistrar
- ImportSelector
-
Aware
-
- ApplicationContextAware
- BeanFactoryAware
-
InitializingBean || @PostConstruct
-
FactoryBean
-
SmartInitializingSingleton
-
ApplicationListener
-
Lifecycle
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- SmartLifecycle
- LifecycleProcessor
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HandlerInterceptor
-
MethodInterceptor
Bean生命周期主线流程:
https://www.processon.com/view/link/5eafa609f346fb177ba8091f
二、Spring扩展点应用场景
2.1 整合Nacos
ApplicationListener扩展场景——监听容器中发布的事件
思考: 为什么整合Nacos注册中心后,服务启动就会自动注册,Nacos是如何实现自动服务注册的?
NacosAutoServiceRegistration
# 对ApplicationListener的扩展
AbstractAutoServiceRegistration#onApplicationEvent
# 服务注册
》NacosServiceRegistry#register
Lifecycle扩展场景——管理具有启动、停止生命周期需求的对象
NacosWatch
#对SmartLifecycle的扩展
NacosWatch#start
#订阅服务接收实例更改的事件
》NamingService#subscribe
扩展: Eureka Server端上下文的初始化是在SmartLifecycle#start中实现的
EurekaServerInitializerConfiguration
Eureka Server源码分析:
https://www.processon.com/view/link/5e5fa095e4b0a967bb35b667
2.2 整合Ribbon
SmartInitializingSingleton扩展场景—— 对容器中的Bean对象进行定制处理
思考:为什么@Bean修饰的RestTemplate加上@LoadBalanced就能实现负载均衡功能?
@Bean
@LoadBalanced
public RestTemplate restTemplate() {
return new RestTemplate();
}
LoadBalancerAutoConfiguration
对SmartInitializingSingleton的扩展,为所有用@LoadBalanced修饰的restTemplate(利用了@Qualifier)绑定实现了负载均衡逻辑的拦截器LoadBalancerInterceptor
LoadBalancerInterceptor
https://www.processon.com/view/link/5e7466dce4b027d999bdaddb
2.3 整合Feign
FactoryBean的扩展场景——将接口生成的代理对象交给Spring管理
思考:为什么Feign接口可以通过@Autowired直接注入使用?Feign接口是如何交给Spring管理的?
@FeignClient(value = "mall-order",path = "/order")
public interface OrderFeignService {
@RequestMapping("/findOrderByUserId/{userId}")
R findOrderByUserId(@PathVariable("userId") Integer userId);
}
@RestController
@RequestMapping("/user")
public class UserController {
@Autowired
OrderFeignService orderFeignService;
@RequestMapping(value = "/findOrderByUserId/{id}")
public R findOrderByUserId(@PathVariable("id") Integer id) {
//feign调用
R result = orderFeignService.findOrderByUserId(id);
return result;
}
}
FeignClientsRegistrar
FeignClientFactorybean
https://www.processon.com/view/link/5e80ae79e4b03b99653fe42f
2.4 整合sentinel
HandlerInterceptor扩展场景——对mvc请求增强
AbstractSentinelInterceptor
# Webmvc接口资源保护入口
AbstractSentinelInterceptor#preHandle
SmartInitializingSingleton&FactoryBean结合场景——根据类型动态装配对象
SentinelDataSourceHandler
# Sentinel持久化读数据源设计,利用了SmartInitializingSingleton扩展点
SentinelDataSourceHandler#afterSingletonsInstantiated
# 注册一个FactoryBean类型的数据源
SentinelDataSourceHandler#registerBean
NacosDataSourceFactoryBean#getObject
# 利用FactoryBean获取到读数据源
new NacosDataSource(properties, groupId, dataId, converter)
NacosDataSourceFactoryBean
https://www.processon.com/view/link/607fef267d9c08283ddc2f8d
2.5 整合seata
AbstractAutoProxyCreator&MethodInterceptor结合场景——实现方法增强
GlobalTransactionScanner
GlobalTransactionalInterceptor
https://www.processon.com/view/link/5f743063e0b34d0711f001d2