关于spring:Spring-IOC

Spring Boot 加载

​ Spring 的 IOC 即管制反转, 外围行将类的创立交给 Spring 工厂.Spring 会扫描 @MapperScan()指定的地址, 将其中所有交给 Spring 容器治理的类 (@Component,@Service,@Controller,@@Configuration 等 …) 以 Bean 的模式放到 Spring 工厂. 当须要某个类的时候, 间接通过 @Resource 或者 @Autowired 即可实现类实例的拆卸. 如果没有指定 @MapperScan(), 默认扫描启动类下所有包及子包.

1. 启动类

@MapperScan("com.trevis.sharding.mapper")
@SpringBootApplication
public class ShardingApplication {public static void main(String[] args) {SpringApplication.run(ShardingApplication.class, args);
    }
}

2. 进入 SpringApplication.Java 构造函数初始化 SpringApplication 对象后调用 run()办法;

public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
        this.resourceLoader = resourceLoader;
        Assert.notNull(primarySources, "PrimarySources must not be null");
        this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
        this.webApplicationType = WebApplicationType.deduceFromClasspath();
        setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
        setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
        this.mainApplicationClass = deduceMainApplicationClass();}

public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {return new SpringApplication(primarySources).run(args);
    }

3. 这里的返回值是 ConfigurableApplicationContext, 即返回利用上下文. 在这里实现 Bean 的拆卸

• Stopwatch: Spring 计时器
• SpringApplicationRunListeners: 监听器
• ApplicationArguments: main 办法启动时携带的参数,args 大多数时候都是空的
• Banner: 启动 banner 图
• context = createApplicationContext(): 创立利用上下文
• prepareContext(): 将主类信息加载到 Spring 容器
• refreshContext(): 将扫描到的须要 Sping 治理的类加载到 IOC 容器

public ConfigurableApplicationContext run(String... args) {StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
   configureHeadlessProperty();
   SpringApplicationRunListeners listeners = getRunListeners(args);
   listeners.starting();
   try {ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
      ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
      configureIgnoreBeanInfo(environment);
      Banner printedBanner = printBanner(environment);
      context = createApplicationContext();
      exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
            new Class[] { ConfigurableApplicationContext.class}, context);
      prepareContext(context, environment, listeners, applicationArguments, printedBanner);
      refreshContext(context);
      afterRefresh(context, applicationArguments);
      stopWatch.stop();
      if (this.logStartupInfo) {new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
      }
      listeners.started(context);
      callRunners(context, applicationArguments);
   }
   catch (Throwable ex) {handleRunFailure(context, ex, exceptionReporters, listeners);
      throw new IllegalStateException(ex);
   }

   try {listeners.running(context);
   }
   catch (Throwable ex) {handleRunFailure(context, ex, exceptionReporters, null);
      throw new IllegalStateException(ex);
   }
   return context;
}

依据初始化构造函数时的 webApplicationType 创立上下文. 这里应该是 SERVLET 容器.

protected ConfigurableApplicationContext createApplicationContext() {
   Class<?> contextClass = this.applicationContextClass;
   if (contextClass == null) {
      try {switch (this.webApplicationType) {
         case SERVLET:
            contextClass = Class.forName(DEFAULT_SERVLET_WEB_CONTEXT_CLASS);
            break;
         case REACTIVE:
            contextClass = Class.forName(DEFAULT_REACTIVE_WEB_CONTEXT_CLASS);
            break;
         default:
            contextClass = Class.forName(DEFAULT_CONTEXT_CLASS);
         }
      }
      catch (ClassNotFoundException ex) {
         throw new IllegalStateException("Unable create a default ApplicationContext, please specify an ApplicationContextClass", ex);
      }
   }
   return (ConfigurableApplicationContext) BeanUtils.instantiateClass(contextClass);
}

获取 context, 依据 webApplicationType 通过反射加载如下类. 这里并没有对于 Bean 工厂的创立, 咱们去他的父类寻找. 如图(略含糊),GenericApplicationContext 是 Bean 工厂的实现类.

在 GenericApplicationContext 找到了 beanFactory;

private final DefaultListableBeanFactory beanFactory;

@Nullable
private ResourceLoader resourceLoader;

private boolean customClassLoader = false;

private final AtomicBoolean refreshed = new AtomicBoolean();


/**
 * Create a new GenericApplicationContext.
 * @see #registerBeanDefinition
 * @see #refresh
 */
public GenericApplicationContext() {this.beanFactory = new DefaultListableBeanFactory();
}

4. 实现 Bean 的注册

从上下文拿到 Bean 工厂

ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();

spring 容器默认笼罩雷同 bean

if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory) beanFactory)
         .setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
}

提早加载, 默认 false

if (this.lazyInitialization) {context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
}

private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,
      SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {context.setEnvironment(environment);
   postProcessApplicationContext(context);
   applyInitializers(context);
   listeners.contextPrepared(context);
   if (this.logStartupInfo) {logStartupInfo(context.getParent() == null);
      logStartupProfileInfo(context);
   }
   // Add boot specific singleton beans
   ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
   beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
   if (printedBanner != null) {beanFactory.registerSingleton("springBootBanner", printedBanner);
   }
   if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory) beanFactory)
            .setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
   }
   if (this.lazyInitialization) {context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());
   }
   // Load the sources
   Set<Object> sources = getAllSources();
   Assert.notEmpty(sources, "Sources must not be empty");
   load(context, sources.toArray(new Object[0]));
   listeners.contextLoaded(context);
}

5.BeanDefinitionLoader

6. 是否被 @Component 注解, 如果是, 注册 bin.(@Controller @Service 等都是 @Component 的子注解)

private int load(Class<?> source) {if (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {// Any GroovyLoaders added in beans{} DSL can contribute beans here
      GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);
      load(loader);
   }
   if (isComponent(source)) {this.annotatedReader.register(source);
      return 1;
   }
   return 0;
}

public void register(Class<?>... componentClasses) {for (Class<?> componentClass : componentClasses) {registerBean(componentClass);
   }
}

public void registerBean(Class<?> beanClass) {doRegisterBean(beanClass, null, null, null, null);
}

7.doRegisterBean 注册 bean

​ 这里看到,Spring 将 bean 放到了 beanDefinitionMap 这个 map 容器中,. 到这里就差不多实现了 bean 注册.

private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
this.beanDefinitionMap.put(beanName, beanDefinition);

8.refreshContext

刷新利用上下文, 注册 bean, 实现 Spring IOC 容器初始化.

1. 筹备刷新 —>2. 获取刷新 bean 工厂 —>3. 筹备 bean 工厂 —>4. 前解决 bean 工厂 —>

5. 调用 bean 工厂前处理器 —>6. 注册 bean 前处理器 —>7. 初始化音讯源 —>8. 初始化利用事件公布器 —>

9. 刷新 —>10. 注册监听器 —>11. 实现 bean 工厂初始化 —>12. 实现刷新.

@Override
public void refresh() throws BeansException, IllegalStateException {synchronized (this.startupShutdownMonitor) {
      // Prepare this context for refreshing.
      prepareRefresh();

      // Tell the subclass to refresh the internal bean factory.
      ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

      // Prepare the bean factory for use in this context.
      prepareBeanFactory(beanFactory);

      try {
         // Allows post-processing of the bean factory in context subclasses.
         postProcessBeanFactory(beanFactory);

         // Invoke factory processors registered as beans in the context.
         invokeBeanFactoryPostProcessors(beanFactory);

         // Register bean processors that intercept bean creation.
         registerBeanPostProcessors(beanFactory);

         // Initialize message source for this context.
         initMessageSource();

         // Initialize event multicaster for this context.
         initApplicationEventMulticaster();

         // Initialize other special beans in specific context subclasses.
         onRefresh();

         // Check for listener beans and register them.
         registerListeners();

         // Instantiate all remaining (non-lazy-init) singletons.
         finishBeanFactoryInitialization(beanFactory);

         // Last step: publish corresponding event.
         finishRefresh();}

      catch (BeansException ex) {if (logger.isWarnEnabled()) {
            logger.warn("Exception encountered during context initialization -" +
                  "cancelling refresh attempt:" + ex);
         }

         // Destroy already created singletons to avoid dangling resources.
         destroyBeans();

         // Reset 'active' flag.
         cancelRefresh(ex);

         // Propagate exception to caller.
         throw ex;
      }

      finally {
         // Reset common introspection caches in Spring's core, since we
         // might not ever need metadata for singleton beans anymore...
         resetCommonCaches();}
   }
}

初始化工厂

protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
   // Tell the internal bean factory to use the context's class loader etc.
   beanFactory.setBeanClassLoader(getClassLoader());
   beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
   beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

   // Configure the bean factory with context callbacks.
   beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
   beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
   beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
   beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
   beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
   beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
   beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);

   // BeanFactory interface not registered as resolvable type in a plain factory.
   // MessageSource registered (and found for autowiring) as a bean.
   beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
   beanFactory.registerResolvableDependency(ResourceLoader.class, this);
   beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
   beanFactory.registerResolvableDependency(ApplicationContext.class, this);

   // Register early post-processor for detecting inner beans as ApplicationListeners.
   beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));

   // Detect a LoadTimeWeaver and prepare for weaving, if found.
   if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
      // Set a temporary ClassLoader for type matching.
      beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
   }

   // Register default environment beans.
   if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
   }
   if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
   }
   if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
   }
}

实现 bean 的注册

invokeBeanFactoryPostProcessors(beanFactory);