源码分析@EnableAutoConfiguration在SpringBoot中的加载和实例化过程

万里长征第一步，我们先理解下什么是EnableAutoConfiguration?

什么是EnableAutoConfiguration注解？

在哪？

org.springframework.boot.autoconfigure.EnableAutoConfiguration

EnableAutoConfiguration概述

我们先来看下源码

package org.springframework.boot.autoconfigure;

import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.context.embedded.EmbeddedServletContainerFactory;
import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
import org.springframework.context.annotation.Conditional;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.core.io.support.SpringFactoriesLoader;

/**
 * Enable auto-configuration of the Spring Application Context, attempting to guess and
 * configure beans that you are likely to need. Auto-configuration classes are usually
 * applied based on your classpath and what beans you have defined. For example, If you
 * have {@code tomcat-embedded.jar} on your classpath you are likely to want a
 * {@link TomcatEmbeddedServletContainerFactory} (unless you have defined your own
 * {@link EmbeddedServletContainerFactory} bean).
 * <p>
 * When using {@link SpringBootApplication}, the auto-configuration of the context is
 * automatically enabled and adding this annotation has therefore no additional effect.
 * <p>
 * Auto-configuration tries to be as intelligent as possible and will back-away as you
 * define more of your own configuration. You can always manually {@link #exclude()} any
 * configuration that you never want to apply (use {@link #excludeName()} if you don't
 * have access to them). You can also exclude them via the
 * {@code spring.autoconfigure.exclude} property. Auto-configuration is always applied
 * after user-defined beans have been registered.
 * <p>
 * The package of the class that is annotated with {@code @EnableAutoConfiguration},
 * usually via {@code @SpringBootApplication}, has specific significance and is often used
 * as a 'default'. For example, it will be used when scanning for {@code @Entity} classes.
 * It is generally recommended that you place {@code @EnableAutoConfiguration} (if you're
 * not using {@code @SpringBootApplication}) in a root package so that all sub-packages
 * and classes can be searched.
 * <p>
 * Auto-configuration classes are regular Spring {@link Configuration} beans. They are
 * located using the {@link SpringFactoriesLoader} mechanism (keyed against this class).
 * Generally auto-configuration beans are {@link Conditional @Conditional} beans (most
 * often using {@link ConditionalOnClass @ConditionalOnClass} and
 * {@link ConditionalOnMissingBean @ConditionalOnMissingBean} annotations).
 */
@SuppressWarnings("deprecation")
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Inherited
@AutoConfigurationPackage
@Import(EnableAutoConfigurationImportSelector.class)
public @interface EnableAutoConfiguration {

	String ENABLED_OVERRIDE_PROPERTY = "spring.boot.enableautoconfiguration";

	/**
	 * Exclude specific auto-configuration classes such that they will never be applied.
	 * @return the classes to exclude
	 */
	Class<?>[] exclude() default {};

	/**
	 * Exclude specific auto-configuration class names such that they will never be
	 * applied.
	 * @return the class names to exclude
	 * @since 1.3.0
	 */
	String[] excludeName() default {};

}

类图

注意“@Import(EnableAutoConfigurationImportSelector.class)” 部分。后边源码分析中会使用到。

说明

EnableAutoConfiguration注解的功能大概如下。

• 开启Spring应该上下文的自动配置，尽可能去加载需要的配置Beans。自动配置类，一般是根据你的classpath路径来应用的。
• 当你使用了SpringBootApplication注解，在context中自动加载配置就已经开启，不需要其他操作。
• 可以通过exclude()传入Class类型；excludeName() 传入名称来排除其他类型的加载。自动加载的配置始终是在普通用户定义的Bean加载之后执行。
• 默认EnableAutoConfiguration扫描的是当前启用注解的Class对象的目录作为root目录。所以这个目录下的所有子目录都会被扫描。
• 自动装载的配置类，也是常规的SpringBean(被@Configuration修饰，@Configuration则被@Component修饰（如果你写的@Configuration在启动类的包名下，开启注解扫描的情况下，也是会把@Configuration注册为Bean对象。）)。当然也可以通过SpringFactoriesLoader的机制来定位到对应的org.springframework.boot.autoconfigure.EnableAutoConfiguration类(不在同用户扫描包目录中)。
• 一般配合Conditional、ConditionalOnClass、ConditionalOnMissingBean一起使用。

测试项目

│  pom.xml
└─src
    └─main
        ├─java
        │  └─com
        │      └─baigt
        │          ├─autoconfig
        │          │      BaigtAutoConfig.java
        │          │      
        │          └─sb
        │                  SBStarter.java
        │                  
        └─resources
            └─META-INF
                    spring.factories

• pom

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.baigt</groupId>
    <artifactId>SpringBootCodeAnalyze</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.14.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

• BaigtAutoConfig

注意和启动类不在一个目录中

package com.baigt.autoconfig;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * 测试Autoconfig
 */
@Configuration
public class BaigtAutoConfig {
    @Bean
    public String env(){
        return new String("Baigt Test");
    }
}

• SBStarter

注意和config不在一个目录 中

package com.baigt.sb;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

/**
 * 测试@EnableAutoConfig加载的流程(加载自定义的配置类，不在同一个目录中)
 */
@SpringBootApplication
public class SBStarter{
    public static void main(String[] args) {
        SpringApplication sb=new SpringApplication(SBStarter.class);
        ConfigurableApplicationContext run = sb.run(args);
        System.out.println(run.getBean("baigt",String.class));
    }

}

• spring.factories

# Auto Configure
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
com.baigt.autoconfig.BaigtAutoConfig

正题(源码)

我们只分析和EnableAutoConfiguration相关的源码。

new SpringApplication

初始化环境(是否是web)，设置ApplicationContextInitializer、ApplicationListener，设置启动类的class到mainApplicationClass上。我们的例子中不是web环境。

	//初始化入口
	public SpringApplication(Object... sources) {
		initialize(sources);
	}
	
	private void initialize(Object[] sources) {
		if (sources != null && sources.length > 0) {
			this.sources.addAll(Arrays.asList(sources));
		}
		this.webEnvironment = deduceWebEnvironment();
		setInitializers((Collection) getSpringFactoriesInstances(
				ApplicationContextInitializer.class));
		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
		this.mainApplicationClass = deduceMainApplicationClass();
	}

SpringApplication

启动SpringBoot项目，我们这里只关注Context创建和实例化AutoConfig相关的逻辑。注意我们的示例不是Web项目，只是个普通的java项目。

run

这里主要有三处，一个是createApplicationContext，一个是prepareContext，一个是refreshContext。

public ConfigurableApplicationContext run(String... args) {
		//...
		ConfigurableApplicationContext context = null;
		//。。。
		listeners.starting();
		try {
			//....
			//注意这部分  创建context
			context = createApplicationContext();
			analyzers = new FailureAnalyzers(context);
			prepareContext(context, environment, listeners, applicationArguments,
					printedBanner);
			//刷新context(实例化各种post以及Bean)
			refreshContext(context);
			afterRefresh(context, applicationArguments);
			// ...
			return context;
		}
		catch (Throwable ex) {
		}
	}

后边再讲refreshContext。

createApplicationContext

创建Context，我们不是web项目哦。所以我们Context是AnnotationConfigApplicationContext类型。

public static final String DEFAULT_CONTEXT_CLASS = "org.springframework.context."
			+ "annotation.AnnotationConfigApplicationContext";
	protected ConfigurableApplicationContext createApplicationContext() {
		Class<?> contextClass = this.applicationContextClass;
		if (contextClass == null) {
			try {
				//前边我们分析到，不是web 环境！！ 所以我们Context是AnnotationConfigApplicationContext类型。
				contextClass = Class.forName(this.webEnvironment
						? DEFAULT_WEB_CONTEXT_CLASS : DEFAULT_CONTEXT_CLASS);
			}
			catch (ClassNotFoundException ex) {
			//
			}
		}//这里实例化的是 AnnotationConfigApplicationContext类(无参构造)
		return (ConfigurableApplicationContext) BeanUtils.instantiate(contextClass);
	}

AnnotationConfigApplicationContext

类图

我们先看下类图。

• 是BeanDefinitionRegistry
• 是BeanFactory
• 是Resource

AnnotationConfigApplicationContext()

从前边我们了解到，我们的context是AnnotationConfigApplicationContext，无参构造会实例化AnnotatedBeanDefinitionReader和ClassPathBeanDefinitionScanner。因为Autoconfig相关的都会被@Configuration修饰，所以我们只关注AnnotatedBeanDefinitionReader，它是注解BeanDefinition读取器。我们主要分析说明的是这个。

	public AnnotationConfigApplicationContext() {
		this.reader = new AnnotatedBeanDefinitionReader(this);
		this.scanner = new ClassPathBeanDefinitionScanner(this);
	}

AnnotatedBeanDefinitionReader

AnnotatedBeanDefinitionReader(BeanDefinitionRegistry)

AnnotationConfigApplicationContext就是一个BeanDefinitionRegistry实例。将AnnotationConfigApplicationContext的实例传递到AnnotatedBeanDefinitionReader中使用。下边我们分析这个AnnotatedBeanDefinitionReader类实例化过程中都做了什么。

	public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry) {
		this(registry, getOrCreateEnvironment(registry));
	}
	public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
		Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
		Assert.notNull(environment, "Environment must not be null");
		this.registry = registry;
		this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
		AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
	}

AnnotationConfigUtils

registerAnnotationConfigProcessors

注册注解相关的后置处理器，比如ConfigurationClassPostProcessor、AutowiredAnnotationBeanPostProcessor、RequiredAnnotationBeanPostProcessor、CommonAnnotationBeanPostProcessor、PersistenceAnnotationBeanPostProcessor、EventListenerMethodProcessor、DefaultEventListenerFactory等。我们这里只关注配置类相关的源码部分。

	public static void registerAnnotationConfigProcessors(BeanDefinitionRegistry registry) {
		registerAnnotationConfigProcessors(registry, null);
	}
	
	public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
			BeanDefinitionRegistry registry, Object source) {

		DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
		Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(4);
		// 注册ConfigurationClassPostProcessor处理器 
		if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
			RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
			def.setSource(source);
			beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
		}
		return beanDefs;
	}
	

ConfigurationClassPostProcessor

类图

• 是BeanDefinitionRegistryPostProcessor
• 是BeanFactoryPostProcessor
• 是PriorityOrdered
• 上边两个接口，是关键，后边要用到!!!!

registerPostProcessor

注册ConfigurationClassPostProcessor处理器到BeanFactory中。

	private static BeanDefinitionHolder registerPostProcessor(
			BeanDefinitionRegistry registry, RootBeanDefinition definition, String beanName) {

		definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
		registry.registerBeanDefinition(beanName, definition);
		return new BeanDefinitionHolder(definition, beanName);
	}

BeanDefinitionRegistry

从入口处我们知道，registry是AnnotationConfigApplicationContext的实例，被传递过来。它的父类是GenericApplicationContext。在无参实例化时，GenericApplicationContext会持有一个DefaultListableBeanFactory对象。

• 结构图

• BeanFactory

GenericApplicationContext的实例化BeanFactory过程

	private final DefaultListableBeanFactory beanFactory;
	public GenericApplicationContext() {
		this.beanFactory = new DefaultListableBeanFactory();
	}
	public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
			throws BeanDefinitionStoreException {

		this.beanFactory.registerBeanDefinition(beanName, beanDefinition);
	}

DefaultListableBeanFactory

registerBeanDefinition

将BeanDefinition定义交给BeanFactory管理。主要在beanDefinitionMap、beanDefinitionNames这几个map对象中存储。

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 ex) {
				throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
						"Validation of bean definition failed", ex);
			}
		}

		BeanDefinition oldBeanDefinition;

		oldBeanDefinition = this.beanDefinitionMap.get(beanName);
		if (oldBeanDefinition != null) {
			if (!isAllowBeanDefinitionOverriding()) {
				throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
						"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
						"': There is already [" + oldBeanDefinition + "] bound.");
			}
			else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
				// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
				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 {
			if (hasBeanCreationStarted()) {
				// Cannot modify startup-time collection elements anymore (for stable iteration)
				synchronized (this.beanDefinitionMap) {
					this.beanDefinitionMap.put(beanName, beanDefinition);
					List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);
					updatedDefinitions.addAll(this.beanDefinitionNames);
					updatedDefinitions.add(beanName);
					this.beanDefinitionNames = updatedDefinitions;
					if (this.manualSingletonNames.contains(beanName)) {
						Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames);
						updatedSingletons.remove(beanName);
						this.manualSingletonNames = updatedSingletons;
					}
				}
			}
			else {
				// Still in startup registration phase
				this.beanDefinitionMap.put(beanName, beanDefinition);
				this.beanDefinitionNames.add(beanName);
				this.manualSingletonNames.remove(beanName);
			}
			this.frozenBeanDefinitionNames = null;
		}

		if (oldBeanDefinition != null || containsSingleton(beanName)) {
			resetBeanDefinition(beanName);
		}
	}

至此ConfigurationClassPostProcessor已经被BeanFactory管理起来。下边我们再来分析后边这个对象是怎么使用。那么我们再次回到SpringApplication的Run方法中prepareContext和**refreshContext(context);**部分。

SpringApplication

prepareContext

我们重点关注下load部分，传入的是当前启动类。source是new SpringApplication时传入的Class对象，也就是SBStarter.class。

	private void prepareContext(ConfigurableApplicationContext context,
			ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
			ApplicationArguments applicationArguments, Banner printedBanner) {
		//。。。。。
		// Load the sources
		Set<Object> sources = getSources();
		Assert.notEmpty(sources, "Sources must not be empty");
		load(context, sources.toArray(new Object[sources.size()]));
		// 。。。。
	}

load

加载bean到ApplicationContext中.BeanDefinitionLoader是持有Context对象的。Context本身就是个registry.

protected void load(ApplicationContext context, Object[] sources) {
		if (logger.isDebugEnabled()) {
			logger.debug(
					"Loading source " + StringUtils.arrayToCommaDelimitedString(sources));
		}
		BeanDefinitionLoader 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);
		}
		loader.load();
	}

BeanDefinitionLoader

load

我们的source就是SBStarter.class,也就是会执行load((Class<?>) source)。最后注册成类型AnnotatedBeanDefinition的BeanDefinition。

	public int load() {
		int count = 0;
		for (Object source : this.sources) {
			count += load(source);
		}
		return count;
	}
	private int load(Object source) {
		Assert.notNull(source, "Source must not be null");
		if (source instanceof Class<?>) {
			return load((Class<?>) source);
		}
		if (source instanceof Resource) {
			return load((Resource) source);
		}
		if (source instanceof Package) {
			return load((Package) source);
		}
		if (source instanceof CharSequence) {
			return load((CharSequence) source);
		}
		throw new IllegalArgumentException("Invalid source type " + source.getClass());
	}

	private int load(Class<?> source) {
		if (isGroovyPresent()) {
			// Any GroovyLoaders added in beans{} DSL can contribute beans here
			if (GroovyBeanDefinitionSource.class.isAssignableFrom(source)) {
				GroovyBeanDefinitionSource loader = BeanUtils.instantiateClass(source,
						GroovyBeanDefinitionSource.class);
				load(loader);
			}
		}
		//如果SBStarter是个组件的话，会注册到beanDefinition上去。
		if (isComponent(source)) {
			//AnnotatedBeanDefinitionReader是前边实例化时创建。目的是注册一个类型AnnotatedBeanDefinition的BeanDefinition
			this.annotatedReader.register(source);
			return 1;
		}
		return 0;
	}

isComponent

• @SpringBootApplication是SpringBootConfiguration类型的。

• SpringBootConfiguration是Configuration类型的。

• Configuration是Component类型的

• 最后SBStarter也就是个Component类型的

AnnotatedBeanDefinitionReader

register

	//annotatedClasses=com.baigt.sb.SBStarter
	public void register(Class<?>... annotatedClasses) {
		for (Class<?> annotatedClass : annotatedClasses) {
			registerBean(annotatedClass);
		}
	}

registerBean

这里我们要注意的是我们是创建了一个AnnotatedGenericBeanDefinition类型的BeanDefinition对象通过BeanDefinitionReaderUtils工具进行注册的。

	public void registerBean(Class<?> annotatedClass) {
		registerBean(annotatedClass, null, (Class<? extends Annotation>[]) null);
	}

	public void registerBean(Class<?> annotatedClass, Class<? extends Annotation>... qualifiers) {
		registerBean(annotatedClass, null, qualifiers);
	}
	
	public void registerBean(Class<?> annotatedClass, String name, Class<? extends Annotation>... qualifiers) {
		//注意这里，我是一个AnnotatedGenericBeanDefinition类型的BeanDefinition实例
		AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass);
		if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
			return;
		}

		ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
		abd.setScope(scopeMetadata.getScopeName());
		String 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));
				}
			}
		}

		BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
		definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
		//我是在这里和context关联上的
		BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
	}

BeanDefinitionReaderUtils

registerBeanDefinition

注意传入的registry,AnnotationConfigApplicationContext本身就是个BeanDefinitionRegistry。而这个部分最后调用的是AnnotationConfigApplicationContext在实例化中隐式实例化父类GenericApplicationContext时创建的一个DefaultListableBeanFactory对象的registerBeanDefinition方法。这就又回到了ConfiguationClassPostProcessor时registerBeanDefinition的过程。因此这里就不再继续深入分析。最终的结果是交给了BeanFactory统一管理BeanDefinition！！

	public static void registerBeanDefinition(
			BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
			throws BeanDefinitionStoreException {

		// Register bean definition under primary name.
		String beanName = definitionHolder.getBeanName();
		registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());

		// Register aliases for bean name, if any.
		String[] aliases = definitionHolder.getAliases();
		if (aliases != null) {
			for (String alias : aliases) {
				registry.registerAlias(beanName, alias);
			}
		}
	}

SpringApplication

refreshContext

刷新Context和注册关机钩子；注意传入的是一个AnnotationConfigApplicationContext实例。我们主要分析refresh

	private void refreshContext(ConfigurableApplicationContext context) {
		refresh(context);
		if (this.registerShutdownHook) {
			try {
				context.registerShutdownHook();
			}
			catch (AccessControlException ex) {
				// Not allowed in some environments.
			}
		}
	}

	protected void refresh(ApplicationContext applicationContext) {
		Assert.isInstanceOf(AbstractApplicationContext.class, applicationContext);
		((AbstractApplicationContext) applicationContext).refresh();
	}

刷新用的是AbstractApplicationContext中的refresh方法。

AbstractApplicationContext

org.springframework.context.support.AbstractApplicationContext

refresh

在ConfigurationClassPostProcessor那一部分，我们知道它是一个BeanFactoryPostProcessor。所以我们一定要看的是invokeBeanFactoryPostProcessors部分的逻辑，其次因为Configuration注解类中相关的如@Bean修饰的方法也是要实例化的，所以我们还要看的是finishBeanFactoryInitialization中的逻辑。

	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// refresh的前置准备，比如设置startTime，开启激活状态、关闭close状态等等等
			prepareRefresh();

			//告诉子类去刷新内容Bean工厂(从类图中可以明显看出来入口类实例也是个bean工厂)
			// 观察和刷新BeanFactory
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			//提前设置一些在该context中使用的属性，比如Classloader、Callback、environment等
			prepareBeanFactory(beanFactory);

			try {
				// 通知context子类，后置处理beanFactory。比如用一系列的Webcontext子类
				postProcessBeanFactory(beanFactory);

				// 将BeanFactoryPostProcessor在当前Context中注册为Bean
				invokeBeanFactoryPostProcessors(beanFactory);

				// 注册BeanPostProcessor来拦截Bean创建的后置处理。
				registerBeanPostProcessors(beanFactory);

				// 为当前Context初始化MessageSource
				initMessageSource();

				// 为当前context初始化应用事件广播
				initApplicationEventMulticaster();

				// 初始化其他特殊的bean对象 比如webcontext
				onRefresh();

				// 检查监听Bean 并发布他们(ApplicationListener)
				registerListeners();

				// 实例化BeanFactory中所有的其他的单例对象集合(非延迟的)
				finishBeanFactoryInitialization(beanFactory);

				// 最后发布LifecycleProcessor和ContextRefreshedEvent事件
				finishRefresh();
			}

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

				// 失败销毁bean
				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();
			}
		}
	}

invokeBeanFactoryPostProcessors

使用委托模式来执行BeanFactoryPostProcessors。注意委托类PostProcessorRegistrationDelegate接收的beanFactory是我们的Context实例(是个BeanFactory，同时它也持有ConfigurationClassPostProcessor的BeanDefinition信息)。getBeanFactoryPostProcessors部分中的BeanFactoryPostProcessors是其他步骤中注入的后置器，我们这里不关注。直接进委托类中继续 分析。

	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

		// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
		// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
		if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
		}
	}

PostProcessorRegistrationDelegate

org.springframework.context.support.PostProcessorRegistrationDelegate

invokeBeanFactoryPostProcessors

我们不关注beanFactoryPostProcessors部分传入的参数，因为ConfigurationClassPostProcessor不在此。前边我们分析到ConfigurationClassPostProcessor同时是一个BeanDefinitionRegistryPostProcessor，invokeBeanFactoryPostProcessors中与此有关的逻辑我们重点看下!!!

• 首先执行实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor
• 其次执行实现Ordered接口的BeanDefinitionRegistryPostProcessor
• 最后执行其他所有的BeanDefinitionRegistryPostProcessor对象

public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

		// Invoke BeanDefinitionRegistryPostProcessors first, if any.
		Set<String> processedBeans = new HashSet<String>();

		if (beanFactory instanceof BeanDefinitionRegistry) {
			BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
			List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
			List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();

			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				//省略
			}

		
			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();

			// 首先执行一个实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessors!!! 这不就是我们的ConfigurationClassPostProcessor嘛!!!
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// 其次执行一个实现Ordered接口的BeanDefinitionRegistryPostProcessors!!! 且没有在processedBeans中
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
			currentRegistryProcessors.clear();

			// 最后执行其他 BeanDefinitionRegistryPostProcessor
			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					if (!processedBeans.contains(ppName)) {
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						processedBeans.add(ppName);
						reiterate = true;
					}
				}
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
				currentRegistryProcessors.clear();
			}

			// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {
			// Invoke factory processors registered with the context instance.
			invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}

		// Do not initialize FactoryBeans here: We need to leave all regular beans
		// uninitialized to let the bean factory post-processors apply to them!
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
		// Ordered, and the rest.
		List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
		List<String> orderedPostProcessorNames = new ArrayList<String>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
		for (String ppName : postProcessorNames) {
			if (processedBeans.contains(ppName)) {
				// skip - already processed in first phase above
			}
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// Finally, invoke all other BeanFactoryPostProcessors.
		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
		for (String postProcessorName : nonOrderedPostProcessorNames) {
			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

		// Clear cached merged bean definitions since the post-processors might have
		// modified the original metadata, e.g. replacing placeholders in values...
		beanFactory.clearMetadataCache();
	}

• 我们只关注第一个，因为ConfigurationClassPostProcessor实现了PriorityOrdered接口!!!!

invokeBeanDefinitionRegistryPostProcessors

传入的postProcessors是ConfigurationClassPostProcessor，传入的registry则是我们的AnnotationConfigApplicationContext（前边也提到了他也是个BeanDefinitionRegistry）。哇偶!终于到了我们ConfigurationClassPostProcessor的源码部分了(postProcessBeanDefinitionRegistry)

	private static void invokeBeanDefinitionRegistryPostProcessors(
			Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {

		for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
			postProcessor.postProcessBeanDefinitionRegistry(registry);
		}
	}

ConfigurationClassPostProcessor

postProcessBeanDefinitionRegistry

这个方法比较简单，有些检查，核心方法是processConfigBeanDefinitions。我们跟进去看下。

	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
		int registryId = System.identityHashCode(registry);
		if (this.registriesPostProcessed.contains(registryId)) {
			throw new IllegalStateException(
					"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
		}
		if (this.factoriesPostProcessed.contains(registryId)) {
			throw new IllegalStateException(
					"postProcessBeanFactory already called on this post-processor against " + registry);
		}
		this.registriesPostProcessed.add(registryId);

		processConfigBeanDefinitions(registry);
	}

processConfigBeanDefinitions

类的Doc说明是构建和验证由Configuration注解修饰的Class对象。注意注入的BeanDefinitionRegistry是一个DefaultListableBeanFactory实例，因此也是一个SingletonBeanRegistry对象。具体可自行分析类图的继承关系。这里会加载我们启动类SBStarter这个配置类。

启动类SBStarter是我们自定义的类，是在org.springframework.boot.SpringApplication#prepareContext步骤中注入的。

	/**
	 * Build and validate a configuration model based on the registry of
	 * {@link Configuration} classes.
	 */
	public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
		List<BeanDefinitionHolder> configCandidates = new ArrayList<BeanDefinitionHolder>();
		String[] candidateNames = registry.getBeanDefinitionNames();

		for (String beanName : candidateNames) {
			BeanDefinition beanDef = registry.getBeanDefinition(beanName);
			//是否已经加载过
			if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
					ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
			
			}
			//没有加载过 就放入configCandidates集合中  这里只有我们手写的启动类SBStarter是没有被加载过的。具体加载过程上边我们已经说过了  我们这里看下SBStarter的后续操作。
			else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
				configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
			}
		}

		// 没有就快速返回
		if (configCandidates.isEmpty()) {
			return;
		}

		// 根据Order排序
		Collections.sort(configCandidates, new Comparator<BeanDefinitionHolder>() {
			@Override
			public int compare(BeanDefinitionHolder bd1, BeanDefinitionHolder bd2) {
				int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
				int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
				return (i1 < i2) ? -1 : (i1 > i2) ? 1 : 0;
			}
		});

		// Detect any custom bean name generation strategy supplied through the enclosing application context
		SingletonBeanRegistry sbr = null;
		if (registry instanceof SingletonBeanRegistry) {
			sbr = (SingletonBeanRegistry) registry;
			if (!this.localBeanNameGeneratorSet && sbr.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) {
				BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
				this.componentScanBeanNameGenerator = generator;
				this.importBeanNameGenerator = generator;
			}
		}

		// 解析每一个 @Configuration class  这里只解析到我们开启SpringBootApplication注解的SBStarter类是Configuration class,我们写的那个不在扫描路径中。
		ConfigurationClassParser parser = new ConfigurationClassParser(
				this.metadataReaderFactory, this.problemReporter, this.environment,
				this.resourceLoader, this.componentScanBeanNameGenerator, registry);

		Set<BeanDefinitionHolder> candidates = new LinkedHashSet<BeanDefinitionHolder>(configCandidates);
		Set<ConfigurationClass> alreadyParsed = new HashSet<ConfigurationClass>(configCandidates.size());
		do {
			//从SBStarter为入口解析Configuration相关Class
			parser.parse(candidates);
			parser.validate();

			Set<ConfigurationClass> configClasses = new LinkedHashSet<ConfigurationClass>(parser.getConfigurationClasses());
			configClasses.removeAll(alreadyParsed);

			// Read the model and create bean definitions based on its content
			if (this.reader == null) {
				this.reader = new ConfigurationClassBeanDefinitionReader(
						registry, this.sourceExtractor, this.resourceLoader, this.environment,
						this.importBeanNameGenerator, parser.getImportRegistry());
			}
			// 在这里加载成BeanDefinition 并交给BeanFactory管理。
			this.reader.loadBeanDefinitions(configClasses);
			alreadyParsed.addAll(configClasses);

			candidates.clear();
			if (registry.getBeanDefinitionCount() > candidateNames.length) {
				String[] newCandidateNames = registry.getBeanDefinitionNames();
				Set<String> oldCandidateNames = new HashSet<String>(Arrays.asList(candidateNames));
				Set<String> alreadyParsedClasses = new HashSet<String>();
				for (ConfigurationClass configurationClass : alreadyParsed) {
					alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
				}
				for (String candidateName : newCandidateNames) {
					if (!oldCandidateNames.contains(candidateName)) {
						BeanDefinition bd = registry.getBeanDefinition(candidateName);
						if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
								!alreadyParsedClasses.contains(bd.getBeanClassName())) {
							candidates.add(new BeanDefinitionHolder(bd, candidateName));
						}
					}
				}
				candidateNames = newCandidateNames;
			}
		}
		while (!candidates.isEmpty());

		// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
		if (sbr != null) {
			if (!sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
				sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
			}
		}

		if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
			((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
		}
	}

ConfigurationClassParser

parse(set)

这里主要分析两个部分，一个是再次Parse(不同入参)，一个是完整流程（processDeferredImportSelectors()）

• SBStarter注入的BeanDefiniton是个AnnotatedBeanDefinition

触发parse(AnnotationMetadata metadata, String beanName)调用

public void parse(Set<BeanDefinitionHolder> configCandidates) {
		this.deferredImportSelectors = new LinkedList<DeferredImportSelectorHolder>();

		for (BeanDefinitionHolder holder : configCandidates) {
			BeanDefinition bd = holder.getBeanDefinition();
			try {
				if (bd instanceof AnnotatedBeanDefinition) {
					parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
				}
				else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
					parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
				}
				else {
					parse(bd.getBeanClassName(), holder.getBeanName());
				}
			}
			catch (BeanDefinitionStoreException ex) {
				throw ex;
			}
			catch (Throwable ex) {
				throw new BeanDefinitionStoreException(
						"Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
			}
		}

		processDeferredImportSelectors();
	}

parse(AnnotationMetadata, String)

	protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
		processConfigurationClass(new ConfigurationClass(metadata, beanName));
	}

processConfigurationClass

处理ConfigurationClass对象。主要是doProcessConfigurationClass部分。

protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
		if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
			return;
		}

		ConfigurationClass existingClass = this.configurationClasses.get(configClass);
		if (existingClass != null) {
			if (configClass.isImported()) {
				if (existingClass.isImported()) {
					existingClass.mergeImportedBy(configClass);
				}
				// Otherwise ignore new imported config class; existing non-imported class overrides it.
				return;
			}
			else {
				// Explicit bean definition found, probably replacing an import.
				// Let's remove the old one and go with the new one.
				this.configurationClasses.remove(configClass);
				for (Iterator<ConfigurationClass> it = this.knownSuperclasses.values().iterator(); it.hasNext();) {
					if (configClass.equals(it.next())) {
						it.remove();
					}
				}
			}
		}

		// Recursively process the configuration class and its superclass hierarchy.
		SourceClass sourceClass = asSourceClass(configClass);
		do {
			sourceClass = doProcessConfigurationClass(configClass, sourceClass);
		}
		while (sourceClass != null);

		this.configurationClasses.put(configClass, configClass);
	}

doProcessConfigurationClass

这里很重要了，也是很复杂的一部分。不过也是SpringBoot可以不使用Xml就能扫描注解相关类的关键部分。下边大概涉及到@PropertySources,@PropertySource,@ComponentScans.class, @ComponentScan.class，@Import,@ImportSource等等。我们主要关注的是@Import部分。为什么？因为我们还是目的就是想看@EnableAutoConfiguration是怎么加载不同目录下的配置类，并实例化的!!! 而在@EnableAutoConfiguration中有使用了@Import,@Import(EnableAutoConfigurationImportSelector.class)

protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
			throws IOException {

		// 处理成员class  比如内部class 静态class
		processMemberClasses(configClass, sourceClass);

		// 处理 @PropertySource annotations
		for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), PropertySources.class,
				org.springframework.context.annotation.PropertySource.class)) {
			if (this.environment instanceof ConfigurableEnvironment) {
				processPropertySource(propertySource);
			}
			else {
				logger.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
						"]. Reason: Environment must implement ConfigurableEnvironment");
			}
		}

		// 处理 @ComponentScan annotations
		Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
		if (!componentScans.isEmpty() &&
				!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
			for (AnnotationAttributes componentScan : componentScans) {
				// The config class is annotated with @ComponentScan -> perform the scan immediately
				Set<BeanDefinitionHolder> scannedBeanDefinitions =
						this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
				// Check the set of scanned definitions for any further config classes and parse recursively if needed
				for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
					BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
					if (bdCand == null) {
						bdCand = holder.getBeanDefinition();
					}
					if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
						parse(bdCand.getBeanClassName(), holder.getBeanName());
					}
				}
			}
		}

		// 处理 any @Import annotations  我们Spring.factories就是在这一部分  会解析出org.springframework.boot.autoconfigure.EnableAutoConfigurationImportSelector
		processImports(configClass, sourceClass, getImports(sourceClass), true);

		// 处理 any @ImportResource annotations  如果手动引入了xml配置文件 基本是这种的
		if (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) {
			AnnotationAttributes importResource =
					AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
			String[] resources = importResource.getStringArray("locations");
			Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
			for (String resource : resources) {
				String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
				configClass.addImportedResource(resolvedResource, readerClass);
			}
		}

		// Process individual @Bean methods
		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
		for (MethodMetadata methodMetadata : beanMethods) {
			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
		}

		// Process default methods on interfaces
		processInterfaces(configClass, sourceClass);

		// Process superclass, if any
		if (sourceClass.getMetadata().hasSuperClass()) {
			String superclass = sourceClass.getMetadata().getSuperClassName();
			if (!superclass.startsWith("java") && !this.knownSuperclasses.containsKey(superclass)) {
				this.knownSuperclasses.put(superclass, configClass);
				// Superclass found, return its annotation metadata and recurse
				return sourceClass.getSuperClass();
			}
		}

		// No superclass -> processing is complete
		return null;
	}

processImports

从EnableAutoConfigurationImportSelector中获取Spring.factories中key=org.springframework.boot.autoconfigure.EnableAutoConfiguration的需要自动化加载的配置类。最后存放在deferredImportSelectors集合中。

private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
			Collection<SourceClass> importCandidates, boolean checkForCircularImports) {

		if (importCandidates.isEmpty()) {
			return;
		}

		if (checkForCircularImports && isChainedImportOnStack(configClass)) {
			this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
		}
		else {
			this.importStack.push(configClass);
			try {
				for (SourceClass candidate : importCandidates) {
					if (candidate.isAssignable(ImportSelector.class)) {
						// Candidate class is an ImportSelector -> delegate to it to determine imports
						Class<?> candidateClass = candidate.loadClass();
						//实例化EnableAutoConfigurationImportSelector  存放在deferredImportSelectors中
						ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
						ParserStrategyUtils.invokeAwareMethods(
								selector, this.environment, this.resourceLoader, this.registry);
						if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
							this.deferredImportSelectors.add(
									new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
						}
						else {
							String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
							Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
							processImports(configClass, currentSourceClass, importSourceClasses, false);
						}
					}
					else {
					//省略代码
					}
				}
			}
			catch (BeanDefinitionStoreException ex) {
				//
			}
			finally {
				this.importStack.pop();
			}
		}
	}

parse(Set<BeanDefinitionHolder> configCandidates)

返回到此处，执行 processDeferredImportSelectors方法。处理刚才存放在deferredImportSelectors中的import对象。

public void parse(Set<BeanDefinitionHolder> configCandidates) {
		this.deferredImportSelectors = new LinkedList<DeferredImportSelectorHolder>();

		for (BeanDefinitionHolder holder : configCandidates) {
			BeanDefinition bd = holder.getBeanDefinition();
			try {
				if (bd instanceof AnnotatedBeanDefinition) {
					parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
				}
				else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
					parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
				}
				else {
					parse(bd.getBeanClassName(), holder.getBeanName());
				}
			}
			catch (BeanDefinitionStoreException ex) {
				throw ex;
			}
		}
		//处理我们刚才存放在这里的deferredImportSelectors
		processDeferredImportSelectors();
	}

processDeferredImportSelectors

调用ImportSelector类的selectImports方法，最后递归调用processImports来处理其他Configuration类。这里我们来看下EnableAutoConfigurationImportSelector的selectImports方法。

private void processDeferredImportSelectors() {
		List<DeferredImportSelectorHolder> deferredImports = this.deferredImportSelectors;
		this.deferredImportSelectors = null;
		Collections.sort(deferredImports, DEFERRED_IMPORT_COMPARATOR);

		for (DeferredImportSelectorHolder deferredImport : deferredImports) {
			ConfigurationClass configClass = deferredImport.getConfigurationClass();
			try {
				String[] imports = deferredImport.getImportSelector().selectImports(configClass.getMetadata());
				processImports(configClass, asSourceClass(configClass), asSourceClasses(imports), false);
			}
			catch (BeanDefinitionStoreException ex) {
				
			}
		}
	}

EnableAutoConfigurationImportSelector

@EnableAutoConfiguration 中@Import引入的ImportSelector。我们Ctrl+F12来看下selectImports方法在哪？

AutoConfigurationImportSelector

EnableAutoConfigurationImportSelector 的父类。selectImports方法所在的类。我们重点关注getCandidateConfigurations方法的源码。通过SpringFactoriesLoader.loadFactoryNames来加载spring.factories中对应key为EnableAutoConfiguration的ConfigClass集合。

public String[] selectImports(AnnotationMetadata annotationMetadata) {
		//如果不是EnableAutoConfigurationImportSelector的时候 isEnabled==true  默认AutoConfigurationImportSelector的isEnable==true ,走后边的逻辑
		if (!isEnabled(annotationMetadata)) {
			return NO_IMPORTS;
		}
		try {
			AutoConfigurationMetadata autoConfigurationMetadata = AutoConfigurationMetadataLoader
					.loadMetadata(this.beanClassLoader);
			AnnotationAttributes attributes = getAttributes(annotationMetadata);
			//获取需要自动化加载配置类 这个是核心类。我们下边分析
			List<String> configurations = getCandidateConfigurations(annotationMetadata,
					attributes);
			//删除重复的configClass		
			configurations = removeDuplicates(configurations);
			//排序
			configurations = sort(configurations, autoConfigurationMetadata);
			Set<String> exclusions = getExclusions(annotationMetadata, attributes);
			//删除exclue掉的Class
			checkExcludedClasses(configurations, exclusions);
			configurations.removeAll(exclusions);
			//处理AutoConfigurationImportFilter
			configurations = filter(configurations, autoConfigurationMetadata);
			//处理AutoConfigurationImportListener
			fireAutoConfigurationImportEvents(configurations, exclusions);
			return configurations.toArray(new String[configurations.size()]);
		}
		catch (IOException ex) {
			throw new IllegalStateException(ex);
		}
	}
	// 通过SpringFactoriesLoader加载EnableAutoConfiguration相关的配置类
	protected List<String> getCandidateConfigurations(AnnotationMetadata metadata,
			AnnotationAttributes attributes) {
		List<String> configurations = SpringFactoriesLoader.loadFactoryNames(
				getSpringFactoriesLoaderFactoryClass(), getBeanClassLoader());
		Assert.notEmpty(configurations,
				"No auto configuration classes found in META-INF/spring.factories. If you "
						+ "are using a custom packaging, make sure that file is correct.");
		return configurations;
	}

	// 要通过SpringFactories来加载的类
	protected Class<?> getSpringFactoriesLoaderFactoryClass() {
		return EnableAutoConfiguration.class;
	}

SpringFactoriesLoader

loadFactoryNames

//从META-INF/spring.factories的文件中解析内容(所有的spring.factories。包括spring-boot-1.5.14.RELEASE.jar中的)。从中拿到org.springframework.boot.autoconfigure.EnableAutoConfiguration对应的配置类，比如我们自己定义的BaigtAutoConfig类。

public static final String FACTORIES_RESOURCE_LOCATION = "META-INF/spring.factories";
	public static List<String> loadFactoryNames(Class<?> factoryClass, ClassLoader classLoader) {
		//factoryClassName=org.springframework.boot.autoconfigure.EnableAutoConfiguration
		String factoryClassName = factoryClass.getName();
		try {
			//从META-INF/spring.factories的文件中解析内容(所有的spring.factories。包括spring-boot-1.5.14.RELEASE.jar中的)
			Enumeration<URL> urls = (classLoader != null ? classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :
					ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));
			List<String> result = new ArrayList<String>();
			while (urls.hasMoreElements()) {
				URL url = urls.nextElement();
				//转换为Properties
				Properties properties = PropertiesLoaderUtils.loadProperties(new UrlResource(url));
				//从properties中获取EnableAutoConfiguration对应的Value  比如我们的com.baigt.autoconfig.BaigtAutoConfig
				String factoryClassNames = properties.getProperty(factoryClassName);
				result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));
			}
			return result;
		}
		catch (IOException ex) {
			
		}
	}

接下来我们返回到ConfigurationClassPostProcessor的processConfigBeanDefinitions方法。

ConfigurationClassPostProcessor

processConfigBeanDefinitions

接下来我们来看下**this.reader.loadBeanDefinitions(configClasses);**加载我们配置类，交给beanFactory管理。

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
		List<BeanDefinitionHolder> configCandidates = new ArrayList<BeanDefinitionHolder>();
		String[] candidateNames = registry.getBeanDefinitionNames();

		//。。。。
		// Parse each @Configuration class
		ConfigurationClassParser parser = new ConfigurationClassParser(
				this.metadataReaderFactory, this.problemReporter, this.environment,
				this.resourceLoader, this.componentScanBeanNameGenerator, registry);

		Set<BeanDefinitionHolder> candidates = new LinkedHashSet<BeanDefinitionHolder>(configCandidates);
		Set<ConfigurationClass> alreadyParsed = new HashSet<ConfigurationClass>(configCandidates.size());
		do {
			parser.parse(candidates);
			parser.validate();

			Set<ConfigurationClass> configClasses = new LinkedHashSet<ConfigurationClass>(parser.getConfigurationClasses());
			configClasses.removeAll(alreadyParsed);

			// Read the model and create bean definitions based on its content
			if (this.reader == null) {
				this.reader = new ConfigurationClassBeanDefinitionReader(
						registry, this.sourceExtractor, this.resourceLoader, this.environment,
						this.importBeanNameGenerator, parser.getImportRegistry());
			}
			this.reader.loadBeanDefinitions(configClasses);
			alreadyParsed.addAll(configClasses);

	}

ConfigurationClassBeanDefinitionReader

loadBeanDefinitions

我们只关注我们定义的配置类(BaigtAutoConfig)

	public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
		TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
		for (ConfigurationClass configClass : configurationModel) {
			loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
		}
	}

loadBeanDefinitionsForConfigurationClass

处理配置类中上的注解(比如Import)，以及@Bean方法

	private void loadBeanDefinitionsForConfigurationClass(
			ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {

		if (trackedConditionEvaluator.shouldSkip(configClass)) {
			String beanName = configClass.getBeanName();
			if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
				this.registry.removeBeanDefinition(beanName);
			}
			this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
			return;
		}
		// BaigtAutoConfig是通过Import(SelectImports)来创建的ConfigClass  所以这里是true
		if (configClass.isImported()) {
			//将该配置类注册为BeanDefinition
			registerBeanDefinitionForImportedConfigurationClass(configClass);
		}
		// BaigtAutoConfig中有个@Bean修饰的方法 也会执行这个方法
		for (BeanMethod beanMethod : configClass.getBeanMethods()) {
			loadBeanDefinitionsForBeanMethod(beanMethod);
		}
		//配置类中如果使用了ImportSource注解和ImportBeanDefinitionRegistrar。则去加载相关内容成BeanDefinition
		loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
		loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
	}

registerBeanDefinitionForImportedConfigurationClass

将BaigtAutoConfig配置类注册为BeanDefinition

private void registerBeanDefinitionForImportedConfigurationClass(ConfigurationClass configClass) {
		AnnotationMetadata metadata = configClass.getMetadata();
		AnnotatedGenericBeanDefinition configBeanDef = new AnnotatedGenericBeanDefinition(metadata);

		ScopeMetadata scopeMetadata = scopeMetadataResolver.resolveScopeMetadata(configBeanDef);
		configBeanDef.setScope(scopeMetadata.getScopeName());
		String configBeanName = this.importBeanNameGenerator.generateBeanName(configBeanDef, this.registry);
		AnnotationConfigUtils.processCommonDefinitionAnnotations(configBeanDef, metadata);

		BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(configBeanDef, configBeanName);
		definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
		// 注册我们的BaigtAutoConfig
		this.registry.registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition());
		configClass.setBeanName(configBeanName);
	}

loadBeanDefinitionsForBeanMethod

解析@Bean方法中相关的属性，比如设置factoryMethod、InitMethod、DestroyMethod、beanName、alias等。也设置lazy、dependOn等等。最后this.registry.registerBeanDefinition(beanName, beanDefToRegister); 完成配置类中@Bean方法的注册。this.registry又是我们前边提到的DefaultListableBeanFactory。交给BeanFactory管理。

	private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
		ConfigurationClass configClass = beanMethod.getConfigurationClass();
		MethodMetadata metadata = beanMethod.getMetadata();
		String methodName = metadata.getMethodName();

		// 这一步(shouldSkip)会设置mergedBeanDefinitions中该name的scope为单例。即使没有这个在最后判断的时候scope=""时也等价于单例
		if (this.conditionEvaluator.shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN)) {
			configClass.skippedBeanMethods.add(methodName);
			return;
		}
		if (configClass.skippedBeanMethods.contains(methodName)) {
			return;
		}

		// Consider name and any aliases
		AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
		List<String> names = new ArrayList<String>(Arrays.asList(bean.getStringArray("name")));
		String beanName = (!names.isEmpty() ? names.remove(0) : methodName);

		// Register aliases even when overridden
		for (String alias : names) {
			this.registry.registerAlias(beanName, alias);
		}

		// Has this effectively been overridden before (e.g. via XML)?
		if (isOverriddenByExistingDefinition(beanMethod, beanName)) {
			if (beanName.equals(beanMethod.getConfigurationClass().getBeanName())) {
				throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
						beanName, "Bean name derived from @Bean method '" + beanMethod.getMetadata().getMethodName() +
						"' clashes with bean name for containing configuration class; please make those names unique!");
			}
			return;
		}

		ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata);
		beanDef.setResource(configClass.getResource());
		beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));

		if (metadata.isStatic()) {
			// static @Bean method
			beanDef.setBeanClassName(configClass.getMetadata().getClassName());
			beanDef.setFactoryMethodName(methodName);
		}
		else {
			// instance @Bean method
			beanDef.setFactoryBeanName(configClass.getBeanName());
			beanDef.setUniqueFactoryMethodName(methodName);
		}
		beanDef.setAutowireMode(RootBeanDefinition.AUTOWIRE_CONSTRUCTOR);
		beanDef.setAttribute(RequiredAnnotationBeanPostProcessor.SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);

		AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);

		Autowire autowire = bean.getEnum("autowire");
		if (autowire.isAutowire()) {
			beanDef.setAutowireMode(autowire.value());
		}

		String initMethodName = bean.getString("initMethod");
		if (StringUtils.hasText(initMethodName)) {
			beanDef.setInitMethodName(initMethodName);
		}

		String destroyMethodName = bean.getString("destroyMethod");
		if (destroyMethodName != null) {
			beanDef.setDestroyMethodName(destroyMethodName);
		}

		// Consider scoping
		ScopedProxyMode proxyMode = ScopedProxyMode.NO;
		AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(metadata, Scope.class);
		if (attributes != null) {
			beanDef.setScope(attributes.getString("value"));
			proxyMode = attributes.getEnum("proxyMode");
			if (proxyMode == ScopedProxyMode.DEFAULT) {
				proxyMode = ScopedProxyMode.NO;
			}
		}

		// Replace the original bean definition with the target one, if necessary
		BeanDefinition beanDefToRegister = beanDef;
		if (proxyMode != ScopedProxyMode.NO) {
			BeanDefinitionHolder proxyDef = ScopedProxyCreator.createScopedProxy(
					new BeanDefinitionHolder(beanDef, beanName), this.registry,
					proxyMode == ScopedProxyMode.TARGET_CLASS);
			beanDefToRegister = new ConfigurationClassBeanDefinition(
					(RootBeanDefinition) proxyDef.getBeanDefinition(), configClass, metadata);
		}

		if (logger.isDebugEnabled()) {
			logger.debug(String.format("Registering bean definition for @Bean method %s.%s()",
					configClass.getMetadata().getClassName(), beanName));
		}

		this.registry.registerBeanDefinition(beanName, beanDefToRegister);
	}

接下来，我们回到 AbstractApplicationContext#refresh

AbstractApplicationContext

refresh

finishBeanFactoryInitialization(beanFactory);

finishBeanFactoryInitialization

通过beanFactory来实例化我们之前交给它管理的BeanDefinition。

protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
		//省略一些代码
		// 实例化一些单例(non-lazyinit)
		beanFactory.preInstantiateSingletons();
	}

DefaultListableBeanFactory

preInstantiateSingletons

实例化beanDefinitionNames中定义BeanDefinition的单例。当然也包含我们的BaigtAutoConfig中对应的@Bean(name="baigt")方法的BeanDefinition

public void preInstantiateSingletons() throws BeansException {
		// 从我们放入到beanDefinitionNames中来遍历进行实例化。
		List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);

		// Trigger initialization of all non-lazy singleton beans...
		for (String beanName : beanNames) {
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
				if (isFactoryBean(beanName)) {
					final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
					boolean isEagerInit;
					if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
						isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
							@Override
							public Boolean run() {
								return ((SmartFactoryBean<?>) factory).isEagerInit();
							}
						}, getAccessControlContext());
					}
					else {
						isEagerInit = (factory instanceof SmartFactoryBean &&
								((SmartFactoryBean<?>) factory).isEagerInit());
					}
					if (isEagerInit) {
						getBean(beanName);
					}
				}
				else {
					// 最后执行这个方法进行实例化
					getBean(beanName);
				}
			}
		}

		// SmartInitializingSingleton的处理
	}

AbstractBeanFactory

getBean

	public Object getBean(String name) throws BeansException {
		return doGetBean(name, null, null, false);
	}

doGetBean

这里我们就是要创建单例的实例(有就从缓存中取)。创建的方式是通过ObjectFactory内部类实现中的createBean方法来完成。我们先看下getSingleton的逻辑。

		// 首次进来为空  最后会走下边的逻辑
		Object sharedInstance = getSingleton(beanName);
		// 通过this.beanDefinitionMap得到的  具体可自行查看源码。这里不太花篇幅讲述。
		final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
		//...
		if (mbd.isSingleton()) {
					sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
						@Override
						public Object getObject() throws BeansException {
							try {
							 	//最终创建Bean的逻辑
								return createBean(beanName, mbd, args);
							}
							catch (BeansException ex) {
								destroySingleton(beanName);
								throw ex;
							}
						}
					});
					bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
				}
	//....		
	// 注意这里，会把单例cache起来，在后边可以直接使用
	if (newSingleton) {
		addSingleton(beanName, singletonObject);
	}

DefaultSingletonBeanRegistry

getSingleton

这里我们要分析的核心逻辑(instance singleton)是调用的了ObjectFactory.getObject，即我们上边的内部类，而内部类的实现则是通过createBean完成。我们再来看下createBean的逻辑。

			try {
					//回到了AbstractBeanFactory#doGetBean的ObjectFactory的getObject方法，执行其中的createBean方法
					singletonObject = singletonFactory.getObject();
					newSingleton = true;
				}

AbstractAutowireCapableBeanFactory

createBean

AbstractBeanFactory的子类实现方法

	AbstractAutowireCapableBeanFactory#createBean(java.lang.Class<T>)
	public <T> T createBean(Class<T> beanClass) throws BeansException {
		// Use prototype bean definition, to avoid registering bean as dependent bean.
		RootBeanDefinition bd = new RootBeanDefinition(beanClass);
		bd.setScope(SCOPE_PROTOTYPE);
		bd.allowCaching = ClassUtils.isCacheSafe(beanClass, getBeanClassLoader());
		return (T) createBean(beanClass.getName(), bd, null);
	}

// 接上
protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
		
		RootBeanDefinition mbdToUse = mbd;
		Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
		if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
			mbdToUse = new RootBeanDefinition(mbd);
			mbdToUse.setBeanClass(resolvedClass);
		}
		try {
			mbdToUse.prepareMethodOverrides();
		}
		catch (BeanDefinitionValidationException ex) {
			
		}

		try {
			// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
			Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
			if (bean != null) {
				return bean;
			}
		}
		catch (Throwable ex) {
			
		}
		// 普通Bean的实例创建
		Object beanInstance = doCreateBean(beanName, mbdToUse, args);
		if (logger.isDebugEnabled()) {
			logger.debug("Finished creating instance of bean '" + beanName + "'");
		}
		return beanInstance;
	}

doCreateBean

核心关注instanceWrapper和exposedObject对象的处理过程

	BeanWrapper instanceWrapper = null;
		if (mbd.isSingleton()) {
			instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
		}
		if (instanceWrapper == null) {
			//创建bean实例的Wrapper对象
			instanceWrapper = createBeanInstance(beanName, mbd, args);
		}
		// bean实例在wrapper中已经创建了(不完整)
		final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
		//省略一些代码。。。
		// Initialize the bean instance.
		Object exposedObject = bean;
		try {
			// 注入property到Bean中
			populateBean(beanName, mbd, instanceWrapper);
			if (exposedObject != null) {
				exposedObject = initializeBean(beanName, exposedObject, mbd);
			}
		}
		//省略一些代码。。。
		return exposedObject;

createBeanInstance

instanceWrapper = createBeanInstance(beanName, mbd, args); 该方法是给指定的name的Class创建Bean对象，支持无参、factoryMethod、AutoWireConstructor三种策略。默认执行无参的"instantiateBean"。而我们的BaigtAutoConfig中的@Bean则设置的有FactoryMethodName(我们定义的@Bean的方法名="env")

protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
		// Make sure bean class is actually resolved at this point.
		Class<?> beanClass = resolveBeanClass(mbd, beanName);

		if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
			throw new BeanCreationException(mbd.getResourceDescription(), beanName,
					"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
		}
		//配置类中的@Bean方法是通过下边这种方式实例化的。
		if (mbd.getFactoryMethodName() != null)  {
			return instantiateUsingFactoryMethod(beanName, mbd, args);
		}

		// Shortcut when re-creating the same bean...
		boolean resolved = false;
		boolean autowireNecessary = false;
		if (args == null) {
			synchronized (mbd.constructorArgumentLock) {
				if (mbd.resolvedConstructorOrFactoryMethod != null) {
					resolved = true;
					autowireNecessary = mbd.constructorArgumentsResolved;
				}
			}
		}
		// 一般我们不是FactoryMethod和有参构造(也可以有哈)
		if (resolved) {
			if (autowireNecessary) {
				return autowireConstructor(beanName, mbd, null, null);
			}
			else {
				return instantiateBean(beanName, mbd);
			}
		}

		// Need to determine the constructor...
		Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
		if (ctors != null ||
				mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
				mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
			return autowireConstructor(beanName, mbd, ctors, args);
		}
		//没有特殊处理就使用无参构造实例
		// No special handling: simply use no-arg constructor.
		return instantiateBean(beanName, mbd);
	}

instantiateUsingFactoryMethod

	protected BeanWrapper instantiateUsingFactoryMethod(
			String beanName, RootBeanDefinition mbd, Object[] explicitArgs) {

		return new ConstructorResolver(this).instantiateUsingFactoryMethod(beanName, mbd, explicitArgs);
	}

ConstructorResolver

instantiateUsingFactoryMethod

	BeanWrapperImpl bw = new BeanWrapperImpl();
		this.beanFactory.initBeanWrapper(bw);
//。。。。
Object beanInstance;
	beanInstance = this.beanFactory.getInstantiationStrategy().instantiate(
						mbd, beanName, this.beanFactory, factoryBean, factoryMethodToUse, argsToUse);
	bw.setBeanInstance(beanInstance);
	return bw;					

SimpleInstantiationStrategy

instantiate

最后调用@Bean对应的方法的invoke方法。到此配置类中的@Bean已经实例化完成。

public Object instantiate(RootBeanDefinition bd, String beanName, BeanFactory owner,
			Object factoryBean, final Method factoryMethod, Object... args) {

		try {
			if (System.getSecurityManager() != null) {
				AccessController.doPrivileged(new PrivilegedAction<Object>() {
					@Override
					public Object run() {
						ReflectionUtils.makeAccessible(factoryMethod);
						return null;
					}
				});
			}
			else {
				ReflectionUtils.makeAccessible(factoryMethod);
			}

			Method priorInvokedFactoryMethod = currentlyInvokedFactoryMethod.get();
			try {
				currentlyInvokedFactoryMethod.set(factoryMethod);
				//执行方法
				return factoryMethod.invoke(factoryBean, args);
			}
			finally {
				if (priorInvokedFactoryMethod != null) {
					currentlyInvokedFactoryMethod.set(priorInvokedFactoryMethod);
				}
				else {
					currentlyInvokedFactoryMethod.remove();
				}
			}
		}
		catch (IllegalArgumentException ex) {
			throws ex;
		}
	}

AbstractAutowireCapableBeanFactory

返回到doCreateBean方法

doCreateBean

我们继续看exposedObject处理的内容。装载Bean的Property属性，initBean对象。我们着重看下initializeBean方法。

final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
Object exposedObject = bean;
		try {
			//装载比如Property属性  可以是其他Bean对象，也可能是String等基本属性。  具体见populateBean中的applyPropertyValues方法
			populateBean(beanName, mbd, instanceWrapper);
			if (exposedObject != null) {
				//初始化Bean对象
				exposedObject = initializeBean(beanName, exposedObject, mbd);
			}
		}

initializeBean

• org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#initializeBean(java.lang.String, java.lang.Object, org.springframework.beans.factory.support.RootBeanDefinition)

初始化给定的Bean，（RootBeanDefinition为空时，执行BeanPost）执行wired的相关方法((BeanNameAware、BeanClassLoaderAware、BeanFactoryAware))、执行initMethod。比如InitializingBean#afterPropertiesSet();或者是自定义的init方法。

protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
		if (System.getSecurityManager() != null) {
			AccessController.doPrivileged(new PrivilegedAction<Object>() {
				@Override
				public Object run() {
					invokeAwareMethods(beanName, bean);
					return null;
				}
			}, getAccessControlContext());
		}
		else {
			//执行wire的method(BeanNameAware、BeanClassLoaderAware、BeanFactoryAware)
			invokeAwareMethods(beanName, bean);
		}

		Object wrappedBean = bean;
		if (mbd == null || !mbd.isSynthetic()) {
			wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
		}

		try {
			//执行init方法
			invokeInitMethods(beanName, wrappedBean, mbd);
		}
		catch (Throwable ex) {
			throw new BeanCreationException(
					(mbd != null ? mbd.getResourceDescription() : null),
					beanName, "Invocation of init method failed", ex);
		}
		if (mbd == null || !mbd.isSynthetic()) {
			wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
		}
		return wrappedBean;
	}

invokeInitMethods

org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#invokeInitMethods。执行afterPropertiesSet方法。如果是自定义的init方法，就调用invokeCustomInitMethod。

protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
			throws Throwable {

		boolean isInitializingBean = (bean instanceof InitializingBean);
		if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
			if (logger.isDebugEnabled()) {
				logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
			}
			if (System.getSecurityManager() != null) {
				try {
					AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
						@Override
						public Object run() throws Exception {
							((InitializingBean) bean).afterPropertiesSet();
							return null;
						}
					}, getAccessControlContext());
				}
				catch (PrivilegedActionException pae) {
					throw pae.getException();
				}
			}
			else {
				((InitializingBean) bean).afterPropertiesSet();
			}
		}

		if (mbd != null) {
			String initMethodName = mbd.getInitMethodName();
			if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
					!mbd.isExternallyManagedInitMethod(initMethodName)) {
				invokeCustomInitMethod(beanName, bean, mbd);
			}
		}
	}

AbstractApplicationContext

返回到refresh方法

refresh

至此配置类相关的Bean实例化完成。

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

其他Bean

我们这里只关注的是配置类的加载，普通Bean的加载可以看我的另外一篇文章 彻底弄懂Spring中Bean的解析、创建和使用

结语

分析使用的Spring版本为4.3.18。代码上如有出入，请自行区分。最后如有不对，欢迎指正。 作者：ricky QQ交流群：244930845。