南宁建设局网站,网站建设背景朝阳,河南工程建设信息网站,网页制作模板素材免费文章目录 前言SpringBoot核心源码拓展Initializer拓展监听器ApplicationListenerBeanFactory的后置处理器 Bean的后置处理器AOP其他的拓展点 前言 当我们引入注册中心的依赖#xff0c;比如nacos的时候#xff0c;当我们启动springboot#xff0c;这个服务就会根据配置… 文章目录 前言SpringBoot核心源码拓展Initializer拓展监听器ApplicationListenerBeanFactory的后置处理器 Bean的后置处理器AOP其他的拓展点 前言 当我们引入注册中心的依赖比如nacos的时候当我们启动springboot这个服务就会根据配置文件自动注册到注册中心中这个动作是如何完成的 注册中心使用了SpringBoot中的事件监听机制在springboot初始化的时候完成服务注册
SpringBoot核心源码
public SpringApplication(ResourceLoader resourceLoader, Class?... primarySources) { ...this.primarySources new LinkedHashSet(Arrays.asList(primarySources));// Servletthis.webApplicationType WebApplicationType.deduceFromClasspath(); this.bootstrapRegistryInitializers new ArrayList(this.getSpringFactoriesInstances(BootstrapRegistryInitializer.class)); // 注意这里Initializersthis.setInitializers(this.getSpringFactoriesInstances(ApplicationContextInitializer.class)); // 注意这里 Listenersthis.setListeners(this.getSpringFactoriesInstances(ApplicationListener.class)); this.mainApplicationClass this.deduceMainApplicationClass();
}我们可以看到空的SpringBoot项目有一些initializers以及一些listeners
注意这两行换言之我们只要实现这两个类就可以自定义拓展SpringBoot了
这里和手写Starter都是对SpringBoot的拓展有兴趣的小伙伴可以看这篇文章
拓展Initializer
再看这张图
我们需要研究一下ApplicationContextInitializer这个类
FunctionalInterface
public interface ApplicationContextInitializerC extends ConfigurableApplicationContext { /** * Initialize the given application context. * param applicationContext the application to configure */ void initialize(C applicationContext);
}这样就很清晰了我们尝试手写一个继承类
public class DemoInitializer implements ApplicationContextInitializer { Override public void initialize(ConfigurableApplicationContext applicationContext) { System.out.println(自定义初始化器执行...); ConfigurableEnvironment environment applicationContext.getEnvironment(); MapString, Object map new HashMap(1); map.put(name, sccccc); environment.getPropertySources().addLast(new MapPropertySource(DemoInitializer, map)); System.out.println(DemoInitializer execute, and add some property); }
}通过SPI机制将自定义初始化器交给list集合initializers
然后再debug就会发现
最后经过一次回调:
private void prepareContext(DefaultBootstrapContext bootstrapContext, ConfigurableApplicationContext context, ... applyInitializers(context); ...// Add boot specific singleton beans 下面是beanFactory的操作遍历所有的初始化器然后
/**
* Apply any {link ApplicationContextInitializer}s to the context before it is
* refreshed.
* param context the configured ApplicationContext (not refreshed yet)
* see ConfigurableApplicationContext#refresh()
*/
SuppressWarnings({ rawtypes, unchecked })
protected void applyInitializers(ConfigurableApplicationContext context) { for (ApplicationContextInitializer initializer : getInitializers()) { Class? requiredType GenericTypeResolver.resolveTypeArgument(initializer.getClass(), ApplicationContextInitializer.class); Assert.isInstanceOf(requiredType, context, Unable to call initializer.); initializer.initialize(context); }
}流程
拓展监听器ApplicationListener FunctionalInterface
public interface ApplicationListenerE extends ApplicationEvent extends EventListener { /** * Handle an application event. */ void onApplicationEvent(E event); /** * Create a new {code ApplicationListener} for the given payload consumer. */ static T ApplicationListenerPayloadApplicationEventT forPayload(ConsumerT consumer) { return event - consumer.accept(event.getPayload()); } }这里和上面initializer一样就不演示了
BeanFactory的后置处理器 Bean的后置处理器 Spring Boot解析配置成BeanDefinition的操作在invokeBeanFactoryPostProcessors方法中 自定义BeanFactory的后置处理器:
Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactorybeanFactory) throws BeansException {Arrays.asList(beanFactory.getBeanDefinitionNames()).forEach(beanDefinitionName -System.out.println(beanDefinitionName));System.out.println(BeanFactoryPostProcessor...);}
}自定义Bean的后置处理器
Component
public class MyBeanPostProcessor implements BeanPostProcessor {Overridepublic Object postProcessBeforeInitialization(Object bean, String beanName)throws BeansException {if(beanName.equals(userController)){System.out.println(找到了userController: bean);}return null;}
}AOP
这个相信大家用的比较多可以自定义切面
Aspect
Component
public class LogAspect {// 切入点 Pointcut 可以对Service服务做切面
Pointcut(execution(* com.example.service.*.*(..)))
public void mypointcut(){}// 前置通知
Before(value mypointcut())
public void before(JoinPoint joinPoint){System.out.println([前置通知] 准备开始记录日志...);System.out.println([前置通知] 目标类是: joinPoint.getTarget());System.out.println([前置通知] 目标方法是:joinPoint.getSignature().getName());
}// 后置通知
AfterReturning(value mypointcut())
public void afterReturning(JoinPoint joinPoint){System.out.println([后置通知] 记录日志完成...);System.out.println([后置通知] 目标类是: joinPoint.getTarget());System.out.println([后置通知] 目标方法是:joinPoint.getSignature().getName());
}/*Around(value mypointcut())
public void around(ProceedingJoinPoint joinPoint){System.out.println([环绕通知] 日志记录前的操作...);try {joinPoint.proceed();System.out.println([环绕通知] 日志记录后的操作...);System.out.println([环绕通知] joinPoint.getTarget());System.out.println([环绕通知] joinPoint.getSignature().getName());} catch (Throwable throwable) {System.out.println([环绕通知] 发生异常的操作...);throwable.printStackTrace();}finally {...}
}其他的拓展点
Banner
方法地址 printBanner(env)-bannerPrinter.print-SpringBootBanner#printBanner 可以在resource目录下建立banner.txt文件夹实现自定义Banner
Runners
流程
自定义
Component
public class JackApplicationRunner implements ApplicationRunner {Overridepublic void run(ApplicationArguments args) throws Exception {System.out.println(JackApplicationRunner...);}
}
