现在都是在springboot 中 集成 spirng，那我们就从springboot 开始。
一：springboot 启动main 函数
public static void main(String[] args) throws Exception { SpringApplication.run(AuditCenterWebApp.class, args); }
二：跟踪下来，会进入到springAppliaction 的 run(String... args) 方法。
public ConfigurableApplicationContext run(String... args) { StopWatch stopWatch = new StopWatch(); stopWatch.start(); ConfigurableApplicationContext context = null; Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList(); this.configureHeadlessProperty(); SpringApplicationRunListeners listeners = this.getRunListeners(args); listeners.starting(); Collection exceptionReporters; try { ApplicationArguments applicationArguments = new DefaultApplicationArguments(args); // 组织环境 ConfigurableEnvironment environment = this.prepareEnvironment(listeners, applicationArguments); this.configureIgnoreBeanInfo(environment); // 打印我们设置的banner Banner printedBanner = this.printBanner(environment); /**创建applicationContext 默认webApplicationType 是 SERVLET，
所以返回的是org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext对象*/ context = this.createApplicationContext(); exceptionReporters = this.getSpringFactoriesInstances(SpringBootExceptionReporter.class, new Class[]{ConfigurableApplicationContext.class}, context); // 准备上下文 this.prepareContext(context, environment, listeners, applicationArguments, printedBanner); // 刷新上下文 this.refreshContext(context); this.afterRefresh(context, applicationArguments); stopWatch.stop(); if (this.logStartupInfo) { (new StartupInfoLogger(this.mainApplicationClass)).logStarted(this.getApplicationLog(), stopWatch); } listeners.started(context); this.callRunners(context, applicationArguments); } catch (Throwable var10) { this.handleRunFailure(context, var10, exceptionReporters, listeners); throw new IllegalStateException(var10); } try { listeners.running(context); return context; } catch (Throwable var9) { this.handleRunFailure(context, var9, exceptionReporters, (SpringApplicationRunListeners)null); throw new IllegalStateException(var9); } }
三：准备上下文 this.prepareContext
点击进入，跟踪 this.load(context, sources.toArray(new Object[0])); 方法
private void prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment, SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) { context.setEnvironment(environment); this.postProcessApplicationContext(context); this.applyInitializers(context); listeners.contextPrepared(context); if (this.logStartupInfo) { this.logStartupInfo(context.getParent() == null); this.logStartupProfileInfo(context); } context.getBeanFactory().registerSingleton("springApplicationArguments", applicationArguments); if (printedBanner != null) { context.getBeanFactory().registerSingleton("springBootBanner", printedBanner); } Set<Object> sources = this.getAllSources(); Assert.notEmpty(sources, "Sources must not be empty"); this.load(context, sources.toArray(new Object[0])); listeners.contextLoaded(context); }
四：我们看一下 BeanDefinitionLoader 是如何创建的
protected void load(ApplicationContext context, Object[] sources) { if (logger.isDebugEnabled()) { logger.debug("Loading source " + StringUtils.arrayToCommaDelimitedString(sources)); } BeanDefinitionLoader loader = this.createBeanDefinitionLoader(this.getBeanDefinitionRegistry(context), sources); if (this.beanNameGenerator != null) { loader.setBeanNameGenerator(this.beanNameGenerator); } if (this.resourceLoader != null) { loader.setResourceLoader(this.resourceLoader); } if (this.environment != null) { loader.setEnvironment(this.environment); } loader.load(); }
（1）getBeanDefinitionRegistry，返回的是 BeanDefinitionRegistry 接口。 将 beanDefinitionRegistry 作为参数 创建 BeanDefinitionLoader
BeanDefinitionLoader(BeanDefinitionRegistry registry, Object... sources) { Assert.notNull(registry, "Registry must not be null"); Assert.notEmpty(sources, "Sources must not be empty");
// 此处的source 就是第一步中 SpringApplication.run(AuditCenterWebApp.class,args) 中的 AuditCenterWebApp.class this.sources = sources;
// new 一个注解的读取器 this.annotatedReader = new AnnotatedBeanDefinitionReader(registry); this.xmlReader = new XmlBeanDefinitionReader(registry); if (this.isGroovyPresent()) { this.groovyReader = new GroovyBeanDefinitionReader(registry); } // new Bean定义的扫描器 this.scanner = new ClassPathBeanDefinitionScanner(registry); this.scanner.addExcludeFilter(new BeanDefinitionLoader.ClassExcludeFilter(sources)); }
（2）我们看下AnnotatedBeanDefinitionReader 的创建，AnnotatedBeanDefinitionReader 里注册了 proccess。跟踪代码到 AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
在这个方法里 springboot 注册 了spring 的几个注解 processor, spring的注解分为几类，每一类注解都有相应注解处理器
// configuration 注解，是个引导注解，所以的他的优先级是很高的，@Configuration 就是由他来处理 org.springframework.context.annotation.internalConfigurationAnnotationProcessor -> org.springframework.context.annotation.ConfigurationClassPostProcessor // 自动装配的处理器，可以自动装配带注解的字段，他支持(@Value, @Autowired, @Inject, @Lookup),默认他的require=true org.springframework.context.annotation.internalAutowiredAnnotationProcessor -> org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor // 用来检查java 的bean 的属性值 @Required org.springframework.context.annotation.internalRequiredAnnotationProcessor -> org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor // 这个注解支持许多java注解和jsr-250 注解。@PostConstruct，@PreDestroy，@Resource等 org.springframework.context.annotation.internalCommonAnnotationProcessor -> org.springframework.context.annotation.CommonAnnotationBeanPostProcessor org.springframework.context.event.internalEventListenerProcessor -> org.springframework.context.event.EventListenerMethodProcessor org.springframework.context.event.internalEventListenerFactory -> org.springframework.context.event.DefaultEventListenerFactory
五：好了回到第四步，调用了 BeanDefinitionLoader 的load()方法。再次跟进load()
public int load() { int count = 0; // 此处source 是 AuditCenterWebApp Object[] var2 = this.sources; int var3 = var2.length; for(int var4 = 0; var4 < var3; ++var4) { Object source = var2[var4]; // 将 AuditCenterWebApp 作为入参传入 count += this.load(source); } return count; }
六：这里判断启动类上是否有启动的注解
private int load(Class<?> source) { if (this.isGroovyPresent() && BeanDefinitionLoader.GroovyBeanDefinitionSource.class.isAssignableFrom(source)) { BeanDefinitionLoader.GroovyBeanDefinitionSource loader = (BeanDefinitionLoader.GroovyBeanDefinitionSource)BeanUtils.instantiateClass(source, BeanDefinitionLoader.GroovyBeanDefinitionSource.class); this.load(loader); } // 是否是组件，会根据启动类中是否有启动的注解 或者 根据类的信息本身(类名，构造方法等) if (this.isComponent(source)) { this.annotatedReader.register(new Class[]{source}); return 1; } else { return 0; } }
一直往下跟踪，跟踪到 org.springframework.context.annotation.AnnotatedBeanDefinitionReader#doRegisterBean 方法
这个方法叫doRegisterBean ，根据类型和方法名 可以知道：这个方法是注册 注解处理器的bean定义信息的
<T> void doRegisterBean(Class<T> annotatedClass, @Nullable Supplier<T> instanceSupplier, @Nullable String name, @Nullable Class<? extends Annotation>[] qualifiers, BeanDefinitionCustomizer... definitionCustomizers) {
// 创建bean的定义信息对象(类名，类的元数据对象) AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass); if (!this.conditionEvaluator.shouldSkip(abd.getMetadata())) { abd.setInstanceSupplier(instanceSupplier); ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd); // singleton abd.setScope(scopeMetadata.getScopeName()); // auditCenterWebApp String beanName = name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry); AnnotationConfigUtils.processCommonDefinitionAnnotations(abd); int var10; int var11; // qualifiers == null 上一层写死 if (qualifiers != null) { Class[] var9 = qualifiers; var10 = qualifiers.length; for(var11 = 0; var11 < var10; ++var11) { Class<? extends Annotation> qualifier = var9[var11]; if (Primary.class == qualifier) { abd.setPrimary(true); } else if (Lazy.class == qualifier) { abd.setLazyInit(true); } else { abd.addQualifier(new AutowireCandidateQualifier(qualifier)); } } } BeanDefinitionCustomizer[] var13 = definitionCustomizers; var10 = definitionCustomizers.length; for(var11 = 0; var11 < var10; ++var11) { BeanDefinitionCustomizer customizer = var13[var11]; customizer.customize(abd); } // 将beanDefinition 和 beanName 包装成BeanDefinitionHolder, adb就是bean定义信息对象 BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName); definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry); } }
跟踪 BeanDefinitionReaderUtils.registerBeanDefinition 方法。
GenericApplicationContext 类中 定义的beanFactory是 DefaultListableBeanFactory，所以最后调的是 DefaultListableBeanFactory 的 registerBeanDefinition
public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException { String beanName = definitionHolder.getBeanName(); // 调用的是 GenericApplicationContext 的registerBeanDefinition 方法。 registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition()); String[] aliases = definitionHolder.getAliases(); if (aliases != null) { String[] var4 = aliases; int var5 = aliases.length; for(int var6 = 0; var6 < var5; ++var6) { String alias = var4[var6]; registry.registerAlias(beanName, alias); } } }
这里是开始注册bean 定义信息（注解处理器，启动类 等 基础bean信息），将bean信息注册到
List<String> beanDefinitionNames // bean 定义信息的注册名称 列表，有序
Map<String, BeanDefinition> beanDefinitionMap // bean 定义信息 的映射，无序
Set<String> manualSingletonNames //手动注册的单例名称列表
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { Assert.hasText(beanName, "Bean name must not be empty"); Assert.notNull(beanDefinition, "BeanDefinition must not be null"); if (beanDefinition instanceof AbstractBeanDefinition) { try { ((AbstractBeanDefinition)beanDefinition).validate(); } catch (BeanDefinitionValidationException var9) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", var9); } } //Map<String, BeanDefinition> beanDefinitionMap ，key=bean名称,bean 对象的定义 // bean 定义对象的映射，beanName 是对象的全限定名称 BeanDefinition oldBeanDefinition = (BeanDefinition)this.beanDefinitionMap.get(beanName); if (oldBeanDefinition != null) { // 如果定义了重复的bean 名称，是否允许覆盖，默认true if (!this.isAllowBeanDefinitionOverriding()) { throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName + "': There is already [" + oldBeanDefinition + "] bound."); } if (oldBeanDefinition.getRole() < beanDefinition.getRole()) { if (this.logger.isWarnEnabled()) { this.logger.warn("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else if (!beanDefinition.equals(oldBeanDefinition)) { if (this.logger.isInfoEnabled()) { this.logger.info("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } } else if (this.logger.isDebugEnabled()) { this.logger.debug("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]"); } this.beanDefinitionMap.put(beanName, beanDefinition); } else { // 注册工作是否已经启动 if (this.hasBeanCreationStarted()) { synchronized(this.beanDefinitionMap) { this.beanDefinitionMap.put(beanName, beanDefinition); List<String> updatedDefinitions = new ArrayList(this.beanDefinitionNames.size() + 1); updatedDefinitions.addAll(this.beanDefinitionNames); updatedDefinitions.add(beanName); this.beanDefinitionNames = updatedDefinitions; if (this.manualSingletonNames.contains(beanName)) { Set<String> updatedSingletons = new LinkedHashSet(this.manualSingletonNames); updatedSingletons.remove(beanName); this.manualSingletonNames = updatedSingletons; } } } else { // 正常的话，会走到这里。设置bean 的名称和定义 this.beanDefinitionMap.put(beanName, beanDefinition); // bean定义的名称列表 this.beanDefinitionNames.add(beanName); this.manualSingletonNames.remove(beanName); } this.frozenBeanDefinitionNames = null; } if (oldBeanDefinition != null || this.containsSingleton(beanName)) { this.resetBeanDefinition(beanName); } }
ok，总结下 this.prepareContext 主要做的事情
环境预处理
创建系统上下文
打印banner
预加载，注册 基础bean定义 (注解处理器，启动类，bean名称处理器 等)
设置上下文监听