『SpringBoot 源码分析』run() 方法执行流程：（2）刷新应用上下文-准备阶段

『SpringBoot 源码分析』run() 方法执行流程：（2）刷新应用上下文-准备阶段

• 基于 2.2.9.RELEASE
• 问题：当方法进行了注释标记之后，springboot 又是怎么注入到容器中并创建类呢？

1. 首先创建测试主程序

package com.lagou;@SpringBootApplication//标注在类上说明这个类是`SpringBoot`的主配置类
public class SpringBootMytestApplication{public static void main(String[] args) {SpringApplication.run(SpringBootMytestApplication.class, args);}
}

2. 创建测试 Controller

package com.lagou.controller;@RestController
public class TestController {@RequestMapping("/test")public String test(){System.out.println("源码环境构建成功...");return "源码环境构建成功";}
}

准备阶段

1. 当准备完成应用上下文环境，以及应用上下文以后，需要为应用上下文做个准备阶段，简单来说其实就是要配置应用上下文，把需要的类装配上

public class SpringApplication {...public ConfigurableApplicationContext run(String... args) {...try {// 将运行时参数封装ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);// 构造应用上下文环境ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);// 处理需要忽略的 BeanconfigureIgnoreBeanInfo(environment);// 打印 bannerBanner printedBanner = printBanner(environment);// 刷新应用上下文前的准备阶段context = createApplicationContext();// 实例化 SpringBootExceptionReporter.class，用来支持报告关于启动的错误exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,new Class[] { ConfigurableApplicationContext.class }, context);// 1. 刷新应用上下文前的准备阶段prepareContext(context, environment, listeners, applicationArguments, printedBanner);...}catch (Throwable ex) {...}...}
}

2. 在对应用上下文进行处理时，主要执行了下面几步的装配

• 把上下文环境设置到应用上下文中
• 执行容器后置处理
• 把应用上下文交给 SpringApplication 初始化收集的 org.springframework.context.ApplicationContextInitializer 所有实现类进行初始化工作
• 利用 org.springframework.boot.context.event.EventPublishingRunListener 向 org.springframework.context.ApplicationListener 发布容器准备好事件

public class SpringApplication {...// 完成属性设置 bean对象创建private void  prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {// 1. 设置容器环境context.setEnvironment(environment);// 2. 执行容器后置处理postProcessApplicationContext(context);// 3. 执行一些初始化器applyInitializers(context); // 4. 向各个监听器发送容器已经准备好的事件listeners.contextPrepared(context);...}
}

• 执行容器后置处理：其实只是往 BeanFactory 添加了基础的转换器

public class SpringApplication {private BeanNameGenerator beanNameGenerator;private ResourceLoader resourceLoader;private boolean addConversionService = true;...protected void postProcessApplicationContext(ConfigurableApplicationContext context) {if (this.beanNameGenerator != null) {context.getBeanFactory().registerSingleton(AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR,this.beanNameGenerator);}if (this.resourceLoader != null) {if (context instanceof GenericApplicationContext) {((GenericApplicationContext) context).setResourceLoader(this.resourceLoader);}if (context instanceof DefaultResourceLoader) {((DefaultResourceLoader) context).setClassLoader(this.resourceLoader.getClassLoader());}}if (this.addConversionService) { // 1. 设置了转换器，例如平时能把整数字符串转换为整形，设置转换器context.getBeanFactory().setConversionService(ApplicationConversionService.getSharedInstance());}}
}

• 执行一些初始化器：就是遍历 org.springframework.context.ApplicationContextInitializer 执行 initialize() 方法

public class SpringApplication {...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);}}
}

• 向各个监听器发送容器已经准备好的事件：就是 org.springframework.boot.context.event.EventPublishingRunListener 向 org.springframework.context.ApplicationListener 发布容器准备好事件

public class SpringApplication {...// 1. 当 ApplicationContext 构建完成时，该方法被调用void contextPrepared(ConfigurableApplicationContext context) {for (SpringApplicationRunListener listener : this.listeners) {listener.contextPrepared(context);}}
}

3. 发布完监听之后，从上下文中获取 IOC 工厂，并设置允许 bean 定义被覆盖参数

public class SpringApplication {...// 完成属性设置 bean 对象创建private void  prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {// 设置容器环境context.setEnvironment(environment);// 执行容器后置处理postProcessApplicationContext(context);// 执行一些初始化器applyInitializers(context); // 向各个监听器发送容器已经准备好的事件listeners.contextPrepared(context);if (this.logStartupInfo) {logStartupInfo(context.getParent() == null);logStartupProfileInfo(context);}// 1. 获取 IOC 容器ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();// 将 main() 函数中的 args 参数封装成单例 Bean，注册进容器beanFactory.registerSingleton("springApplicationArguments", applicationArguments);if (printedBanner != null) {// 将 printedBanner 也封装成单例，注册进容器beanFactory.registerSingleton("springBootBanner", printedBanner);}// 2. 设置允许 bean 定义被覆盖参数if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory) beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);}...}
}

4. 然后加载启动类，并将启动类注入到容器当中，然后发布容器已加载事件

public class SpringApplication {...// 完成属性设置 bean 对象创建private void  prepareContext(ConfigurableApplicationContext context, ConfigurableEnvironment environment,SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments, Banner printedBanner) {// 设置容器环境context.setEnvironment(environment);// 执行容器后置处理postProcessApplicationContext(context);// 执行一些初始化器applyInitializers(context); // 向各个监听器发送容器已经准备好的事件listeners.contextPrepared(context);if (this.logStartupInfo) {logStartupInfo(context.getParent() == null);logStartupProfileInfo(context);}// 获取 IOC 容器ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();// 将 main() 函数中的 args 参数封装成单例 Bean，注册进容器beanFactory.registerSingleton("springApplicationArguments", applicationArguments);if (printedBanner != null) {// 将 printedBanner 也封装成单例，注册进容器beanFactory.registerSingleton("springBootBanner", printedBanner);}// 设置允许 bean 定义被覆盖参数if (beanFactory instanceof DefaultListableBeanFactory) {((DefaultListableBeanFactory) beanFactory).setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);}if (this.lazyInitialization) { // 是否需要进行懒加载，这里不是context.addBeanFactoryPostProcessor(new LazyInitializationBeanFactoryPostProcessor());}// 1. 加载源，这里拿到的是主类，com.lagou.SpringBootMytestApplicationSet<Object> sources = getAllSources();Assert.notEmpty(sources, "Sources must not be empty");// 2. 加载我们的启动类，将启动类注入容器 重点关注load(context, sources.toArray(new Object[0]));// 取出第一个元素，就是主类，要先实例化主类，灌入容器中// 3. 发布容器已加载事件listeners.contextLoaded(context);}
}

• 其中将启动类注入到容器当中是比较关键的一步，首先先把 ApplicationContext 转换成 BeanDefinitionRegistry，然后创建 bean 定义加载器

public class SpringApplication {...protected void load(ApplicationContext context, Object[] sources) {if (logger.isDebugEnabled()) {logger.debug("Loading source " + StringUtils.arrayToCommaDelimitedString(sources));}// 2. 创建 BeanDefinitionLoaderBeanDefinitionLoader loader = createBeanDefinitionLoader(getBeanDefinitionRegistry(context), sources);...}private BeanDefinitionRegistry getBeanDefinitionRegistry(ApplicationContext context) {// 1. 将 ApplicationContext 转换成 BeanDefinitionRegistryif (context instanceof BeanDefinitionRegistry) {return (BeanDefinitionRegistry) context;}if (context instanceof AbstractApplicationContext) {return (BeanDefinitionRegistry) ((AbstractApplicationContext) context).getBeanFactory();}throw new IllegalStateException("Could not locate BeanDefinitionRegistry");}
}

• 创建 BeanDefinitionLoader 主要是把 BeanDefinitionRegistry 以及主类的 sources 进行赋值初始化

public class SpringApplication {private final Object[] sources;private final AnnotatedBeanDefinitionReader annotatedReader;private final XmlBeanDefinitionReader xmlReader;private BeanDefinitionReader groovyReader;private final ClassPathBeanDefinitionScanner scanner;private ResourceLoader resourceLoader;...protected BeanDefinitionLoader createBeanDefinitionLoader(BeanDefinitionRegistry registry, Object[] sources) {// 1. 创建 bean 定义加载器return new BeanDefinitionLoader(registry, sources);}BeanDefinitionLoader(BeanDefinitionRegistry registry, Object... sources) {// 其中，sources 就是主类 com.lagou.SpringBootMytestApplicationAssert.notNull(registry, "Registry must not be null");Assert.notEmpty(sources, "Sources must not be empty");this.sources = sources;// 2. 注解形式的 Bean 定义读取器 比如：@Configuration @Bean @Component @Controller @Service等等this.annotatedReader = new AnnotatedBeanDefinitionReader(registry);// 3. XML 形式的 Bean 定义读取器this.xmlReader = new XmlBeanDefinitionReader(registry);if (isGroovyPresent()) {this.groovyReader = new GroovyBeanDefinitionReader(registry);}// 4. 类路径扫描器this.scanner = new ClassPathBeanDefinitionScanner(registry);// 5. 扫描器添加排除过滤器this.scanner.addExcludeFilter(new ClassExcludeFilter(sources));}
}

5. 创建 BeanDefinitionLoader 成功后，就可以开始执行 load()，这里主要是先把主类注册到 IOC 容器中去

public class SpringApplication {private BeanNameGenerator beanNameGenerator;...protected void load(ApplicationContext context, Object[] sources) {if (logger.isDebugEnabled()) {logger.debug("Loading source " + StringUtils.arrayToCommaDelimitedString(sources));}// 创建 BeanDefinitionLoaderBeanDefinitionLoader loader = createBeanDefinitionLoader(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);}// 1. 执行 load()loader.load();}
}

• 其中 load() 通过 AnnotatedBeanDefinitionReader 将主类 source 注册进 beanDefinitionMap 中

class BeanDefinitionLoader {private final AnnotatedBeanDefinitionReader annotatedReader;...int load() {int count = 0;for (Object source : this.sources) {count += load(source);}return count;}// 根据加载不同类型调用不同的方法private int load(Object source) {Assert.notNull(source, "Source must not be null");// 1. 从 Class 加载if (source instanceof Class<?>) {return load((Class<?>) source);}...}private int load(Class<?> source) {// source 就是 class com.lagou.SpringBootMytestApplicationif (isGroovyPresent() && GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {// Any GroovyLoaders added in beans{} DSL can contribute beans hereGroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source, GroovyBeanDefinitionSource.class);load(loader);}if (isComponent(source)) { // 判断方法有没有标记 Component 注解// 1. 将启动类的 BeanDefinition 注册进 beanDefinitionMapthis.annotatedReader.register(source);return 1;}return 0;}
}

• 调用 register() 方法时，真正会传到 doRegisterBean() 进行执行。首先会把主类转换成 AnnotatedGenericBeanDefinition，然后获取主类的名称，把名称和 AnnotatedGenericBeanDefinition 封装成 BeanDefinitionHolder 后，注册到上下文中

public class AnnotatedBeanDefinitionReader {...public void register(Class<?>... componentClasses) {for (Class<?> componentClass : componentClasses) {registerBean(componentClass);}}public void registerBean(Class<?> beanClass) {doRegisterBean(beanClass, null, null, null, null);}private <T> void doRegisterBean(Class<T> beanClass, @Nullable String name,@Nullable Class<? extends Annotation>[] qualifiers, @Nullable Supplier<T> supplier,@Nullable BeanDefinitionCustomizer[] customizers) {// 1. 把主类转换成 AnnotatedGenericBeanDefinition，其中 beanClass 为 com.lagou.SpringBootMytestApplicationAnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass);if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {return;}abd.setInstanceSupplier(supplier);ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);abd.setScope(scopeMetadata.getScopeName());// 2. 获取类名 springBootMytestApplicationString beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);if (qualifiers != null) {for (Class<? extends Annotation> qualifier : qualifiers) {if (Primary.class == qualifier) {abd.setPrimary(true);}else if (Lazy.class == qualifier) {abd.setLazyInit(true);}else {abd.addQualifier(new AutowireCandidateQualifier(qualifier));}}}if (customizers != null) {for (BeanDefinitionCustomizer customizer : customizers) {customizer.customize(abd);}}// 3. 封装成 BeanDefinitionHolder BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);// 4. 注册到容器中		BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);}
}

• 注册到容器中，简单而言就是调用 BeanDefinitionRegistry 把 BeanDefinitionHolder 的 name 和 AnnotatedGenericBeanDefinition 装配进去

public abstract class BeanDefinitionReaderUtils {...public static void registerBeanDefinition(BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry) throws BeanDefinitionStoreException {// 1. 获取名称 springBootMytestApplicationString beanName = definitionHolder.getBeanName();// 2. 注册到 IOC 容器中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);}}}
}

• 最后会把 name 和 AnnotatedGenericBeanDefinition 存入到 beanDefinitionMap 中

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {...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");// 1. 先校验 beanDefinition 是否合法if (beanDefinition instanceof AbstractBeanDefinition) {try {((AbstractBeanDefinition)beanDefinition).validate();} catch (BeanDefinitionValidationException var8) {throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName, "Validation of bean definition failed", var8);}}BeanDefinition existingDefinition = (BeanDefinition)this.beanDefinitionMap.get(beanName);if (existingDefinition != null) {if (!this.isAllowBeanDefinitionOverriding()) {throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);}if (existingDefinition.getRole() < beanDefinition.getRole()) {if (this.logger.isInfoEnabled()) {this.logger.info("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");}} else if (!beanDefinition.equals(existingDefinition)) {if (this.logger.isDebugEnabled()) {this.logger.debug("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");}} else if (this.logger.isTraceEnabled()) {this.logger.trace("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]");}this.beanDefinitionMap.put(beanName, beanDefinition);} else {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;this.removeManualSingletonName(beanName);}} else {// 2. 再把 beanDefinition 放到 beanDefinitionMap 中this.beanDefinitionMap.put(beanName, beanDefinition);this.beanDefinitionNames.add(beanName);this.removeManualSingletonName(beanName);}this.frozenBeanDefinitionNames = null;}if (existingDefinition == null && !this.containsSingleton(beanName)) {if (this.isConfigurationFrozen()) {this.clearByTypeCache();}} else {this.resetBeanDefinition(beanName);}}	
}

6. 总结