曹工说Spring Boot源码系列开讲了（1）-- Bean Definition到底是什么，附spring思维导图分享
写在前面的话 &&About me#
网上写 spring 的文章多如牛毛，为什么还要写呢，因为，很简单，那是人家写的；网上都鼓励你不要造轮子，为什么你还要造呢，因为，那不是你造的。
我不是要造 spring，我只是想把自己学习 spring 的一些感想，一些心得说出来，希望大家看到有不对的地方，请一定不吝赐教。
说说我自己，13 年小本毕业，软件工程专业，校招去了最近疯传的牢厂总部里待了 2 年，15 年越狱出来，某落魄互联网公司（PC 时代风头无两）待了 1 年，慨叹深圳买房之艰难，遂于 16 年底回蓉。趁着热血未冷，去了一家创业公司，9 个月后，欠薪 3 月，靠刷信用卡还贷，不得不含泪辞职；17 年投奔国企，目前从事公共安全相关工作，趁着对技术还有一腔热情，没事写写文章，目前主要兴趣是：分布式、微服务等后端技术；对 k8s 等新技术保持关注；没事参加一些线下技术活动，欢迎大家和我交流。
本系列的源码讲解思路#
本来，我是想分享一些 spring cloud 的东西，但后来发现，我自己在读 spring cloud 的过程中，有些东西也不是理解得很透彻，比如各种 @Enable 注解其实是用到了 spring boot 的东西，然后我觉得应该倒回去先看看 spring boot，然后呢，看 spring boot 的过程中，发现 spring 和 spring boot 其实是一个深度融合，“你中有我，我中有你”的关系，比如 spring boot 启动时，不是会连带启动 spring 容器吗，等等。
我就想着，干脆把 spring boot 系统研究一把算了，我在 github 上找了 spring boot 的工程，克隆到了码云上（速度要快得多），然后自己回退到了 spring boot 的第一个版本，时间大概是 2013 年 4 月，其实这第一个版本，基本的代码也已经成型了，我就拿这个版本的源码在本地 idea 里面看，配套的 spring 版本是 4.0.0，也还行。
我自己加了不少注释在工程里，工程地址在这：
https://gitee.com/ckl111/spring-boot-first-version-learn
工程结构如下：
这个工程我也会一直维护着，我觉得，spring 4.0.0 的版本，暂时对我阅读代码来说，足够了，如果大家大概了解 spring 每个版本的新特性的话，可以发现，spring 4.0 开始，各种注解已经很完善了，现在虽然已经出到 5.2 版本了，但核心的东西也还是没有变化，所以，对我们研读源码，影响不大。如果真的把这个版本能读得差不多了，那想必对 spring /spring boot 的核心也理解差不多了，到时候再读新版本的源码也不迟，是吧。
总体来说：
spring boot 版本，2013 年 4 月，first version。
配套的 spring 版本，4.0.0.BOOTSTRAP-SNAPSHOT
那时候的 spring boot 长什么样子，我这边给个地址（我这已经克隆到码云了）
https://gitee.com/ckl111/spring-boot/tree/fb6b2244707dd5dfad12d62cb6a3c396555270d1/
目前已更新的部分#
曹工说 Spring Boot 源码（1）-- Bean Definition 到底是什么，附 spring 思维导图分享
曹工说 Spring Boot 源码（2）-- Bean Definition 到底是什么，咱们对着接口，逐个方法讲解
曹工说 Spring Boot 源码（3）-- 手动注册 Bean Definition 不比游戏好玩吗，我们来试一下
曹工说 Spring Boot 源码（4）-- 我是怎么自定义 ApplicationContext，从 json 文件读取 bean definition 的？
曹工说 Spring Boot 源码（5）-- 怎么从 properties 文件读取 bean
曹工说 Spring Boot 源码（6）-- Spring 怎么从 xml 文件里解析 bean 的
曹工说 Spring Boot 源码（7）-- Spring 解析 xml 文件，到底从中得到了什么（上）
曹工说 Spring Boot 源码（8）-- Spring 解析 xml 文件，到底从中得到了什么（util 命名空间）
曹工说 Spring Boot 源码（9）-- Spring 解析 xml 文件，到底从中得到了什么（context 命名空间上）
曹工说 Spring Boot 源码（10）-- Spring 解析 xml 文件，到底从中得到了什么（context:annotation-config 解析）
曹工说 Spring Boot 源码（11）-- context:component-scan，你真的会用吗（这次来说说它的奇技淫巧）
曹工说 Spring Boot 源码（12）-- Spring 解析 xml 文件，到底从中得到了什么（context:component-scan 完整解析 )
曹工说 Spring Boot 源码（13）-- AspectJ 的运行时织入（Load-Time-Weaving），基本内容是讲清楚了（附源码）
曹工说 Spring Boot 源码（14）-- AspectJ 的 Load-Time-Weaving 的两种实现方式细细讲解，以及怎么和 Spring Instrumentation 集成
曹工说 Spring Boot 源码（15）-- Spring 从 xml 文件里到底得到了什么（context：load-time-weaver 完整解析）
曹工说 Spring Boot 源码（16）-- Spring 从 xml 文件里到底得到了什么（aop：config 完整解析【上】）
曹工说 Spring Boot 源码（17）-- Spring 从 xml 文件里到底得到了什么（aop：config 完整解析【中】）
曹工说 Spring Boot 源码（18）-- Spring AOP 源码分析三部曲，终于快讲完了 (aop：config 完整解析【下】)
曹工说 Spring Boot 源码（19）-- Spring 带给我们的工具利器，创建代理不用愁（ProxyFactory）
曹工说 Spring Boot 源码（20）-- 码网恢恢，疏而不漏，如何记录 Spring RedisTemplate 每次操作日志
曹工说 Spring Boot 源码（21）-- 为了让大家理解 Spring Aop 利器 ProxyFactory，我已经拼了
曹工说 Spring Boot 源码（22）-- 你说我 Spring Aop 依赖 AspectJ，我依赖它什么了
曹工说 Spring Boot 源码（23）-- ASM 又立功了，Spring 原来是这么递归获取注解的元注解的
曹工说 Spring Boot 源码（24）-- Spring 注解扫描的瑞士军刀，asm 技术实战（上）
曹工说 Spring Boot 源码（25）-- Spring 注解扫描的瑞士军刀，ASM + Java Instrumentation，顺便提提 Jar 包破解
曹工说 Spring Boot 源码（26）-- 学习字节码也太难了，实在不能忍受了，写了个小小的字节码执行引擎
曹工说 Spring Boot 源码（27）-- Spring 的 component-scan，光是 include-filter 属性的各种配置方式，就够玩半天了
spring 思维导图（bean definition 部分）#
因为我这个系列，大概会按照思维导图的流程来走，然后思维导图太大了，我这里先直接贴前面这部分：
思维导图完整链接：https://www.processon.com/view/link/5deeefdee4b0e2c298aa5596
我大概的讲解思路也会是上面那样，从上到下，每个点细细地讲。
正文#
bean definition 是什么#
闲言少叙，进入正题。第一讲，先说说 bean definition 吧，这个东西，实在太重要了，核心的存储结构啊。
大家可以再想一想，spring 当初刚出来的时候，主打的是 ioc 容器，容器里装了啥呢，bean 啊！bean 是什么呢？
恩。。。我也不知道是啥，反正 spring 里拿出来的就是 bean。
行，那 bean 有什么特征吗？
哦，bean 是一个对象，有名字，有 class 类型，有 scope（单例、prototype 那些），有 role（属于应用的 bean、还是 spring 框架的 bean），有是否延迟初始化（lazy-init），有它依赖的其他 bean，如果这个 bean 不好造（不能直接反射生成的话），可能还有个工厂方法和工厂 bean 呢，哎，好像还说漏了，反正挺多的。
那是不是每个 bean 都有这些属性呢？
仔细想想，好像是的吧。
既然都有这些东西，那这个东西感觉像是个模板了，就像是最近写了年终总结，hr 小姐姐就给我们发了模板，上面姓名啊、部门啊、职位啊、述职的基本格式啊，都是固定的，我们只要拿来，填上自己的信息就行了，那我们是不是可以抽象一下，搞个 class 啊，比如下面这样：
package com.learn;import lombok.Data;
@Data
public class SpringDefinition {<span class="token comment">/** * bean class名 */</span> <span class="token class-name">String</span> beanClassName<span class="token punctuation">;</span> <span class="token comment">/** * 工厂bean的名称 */</span> <span class="token class-name">String</span> factoryBeanName<span class="token punctuation">;</span> <span class="token comment">/** * 工厂方法的名称 */</span> <span class="token class-name">String</span> factoryMethodName<span class="token punctuation">;</span> <span class="token comment">/** * singleton/prototype等 */</span> <span class="token class-name">String</span> scope<span class="token punctuation">;</span> <span class="token comment">/** * 是否延迟初始化 */</span> <span class="token keyword">boolean</span> isLazyInit<span class="token punctuation">;</span> <span class="token comment">/** * 依赖的bean */</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> dependsOn<span class="token punctuation">;</span> <span class="token comment">/** * bean的角色，比如：1：框架；2：应用 */</span> <span class="token keyword">int</span> role<span class="token punctuation">;</span> <span class="token comment">/** * 是否为主候选bean */</span> <span class="token keyword">boolean</span> primary<span class="token punctuation">;</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>其他属性}
实话说，是可以的，一些简单的，轻量级 ioc 容器就是这么玩的，但是 spring 作为优秀代码的代表，肯定不能这么 low，接口的抽象性要好得多，方便我们替换不同的实现，该用接口来抽象，肯定要抽象为接口。
下边我们就看看该接口, 先看接口的描述：
* A BeanDefinition describes a bean instance, which has property values, * constructor argument values, and further information supplied by * concrete implementations. * * <p>This is just a minimal interface: The main intention is to allow a * {@link BeanFactoryPostProcessor} such as {@link PropertyPlaceholderConfigurer} * to introspect and modify property values and other bean metadata. * @author Juergen Hoeller * @author Rob Harrop * @since 19.03.2004
这里说的是，bean definition 描述一个 bean 实例的各种属性，尤其声明了：这是一个最小化接口，主要目的是允许 bean factory 后置处理器，对 bean property 和其他元数据进行修改。而且，这是 2004 年的接口，可想而知，是多么核心的 api 了。
再看看具体定义的方法，更好理解：
public interface BeanDefinition extends AttributeAccessor, BeanMetadataElement {<span class="token comment">/** * Return the name of the parent definition of this bean definition, if any. */</span> <span class="token class-name">String</span> <span class="token function">getParentName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Set the name of the parent definition of this bean definition, if any. */</span> <span class="token keyword">void</span> <span class="token function">setParentName</span><span class="token punctuation">(</span><span class="token class-name">String</span> parentName<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return the current bean class name of this bean definition. * <p>Note that this does not have to be the actual class name used at runtime, in * case of a child definition overriding/inheriting the class name from its parent. * Hence, do <i>not</i> consider this to be the definitive bean type at runtime but * rather only use it for parsing purposes at the individual bean definition level. */</span> <span class="token class-name">String</span> <span class="token function">getBeanClassName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Override the bean class name of this bean definition. * <p>The class name can be modified during bean factory post-processing, * typically replacing the original class name with a parsed variant of it. */</span> <span class="token keyword">void</span> <span class="token function">setBeanClassName</span><span class="token punctuation">(</span><span class="token class-name">String</span> beanClassName<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return the factory bean name, if any. */</span> <span class="token class-name">String</span> <span class="token function">getFactoryBeanName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Specify the factory bean to use, if any. */</span> <span class="token keyword">void</span> <span class="token function">setFactoryBeanName</span><span class="token punctuation">(</span><span class="token class-name">String</span> factoryBeanName<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return a factory method, if any. */</span> <span class="token class-name">String</span> <span class="token function">getFactoryMethodName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Specify a factory method, if any. This method will be invoked with * constructor arguments, or with no arguments if none are specified. * The method will be invoked on the specified factory bean, if any, * or otherwise as a static method on the local bean class. * @param factoryMethodName static factory method name, * or {@code null} if normal constructor creation should be used * @see #getBeanClassName() */</span> <span class="token keyword">void</span> <span class="token function">setFactoryMethodName</span><span class="token punctuation">(</span><span class="token class-name">String</span> factoryMethodName<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return the name of the current target scope for this bean, * or {@code null} if not known yet. */</span> <span class="token class-name">String</span> <span class="token function">getScope</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Override the target scope of this bean, specifying a new scope name. * @see #SCOPE_SINGLETON * @see #SCOPE_PROTOTYPE */</span> <span class="token keyword">void</span> <span class="token function">setScope</span><span class="token punctuation">(</span><span class="token class-name">String</span> scope<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return whether this bean should be lazily initialized, i.e. not * eagerly instantiated on startup. Only applicable to a singleton bean. */</span> <span class="token keyword">boolean</span> <span class="token function">isLazyInit</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Set whether this bean should be lazily initialized. * <p>If {@code false}, the bean will get instantiated on startup by bean * factories that perform eager initialization of singletons. */</span> <span class="token keyword">void</span> <span class="token function">setLazyInit</span><span class="token punctuation">(</span><span class="token keyword">boolean</span> lazyInit<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return the bean names that this bean depends on. */</span> <span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> <span class="token function">getDependsOn</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Set the names of the beans that this bean depends on being initialized. * The bean factory will guarantee that these beans get initialized first. */</span> <span class="token keyword">void</span> <span class="token function">setDependsOn</span><span class="token punctuation">(</span><span class="token class-name">String</span><span class="token punctuation">[</span><span class="token punctuation">]</span> dependsOn<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return whether this bean is a candidate for getting autowired into some other bean. */</span> <span class="token keyword">boolean</span> <span class="token function">isAutowireCandidate</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Set whether this bean is a candidate for getting autowired into some other bean. */</span> <span class="token keyword">void</span> <span class="token function">setAutowireCandidate</span><span class="token punctuation">(</span><span class="token keyword">boolean</span> autowireCandidate<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return whether this bean is a primary autowire candidate. * If this value is true for exactly one bean among multiple * matching candidates, it will serve as a tie-breaker. */</span> <span class="token keyword">boolean</span> <span class="token function">isPrimary</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Set whether this bean is a primary autowire candidate. * <p>If this value is true for exactly one bean among multiple * matching candidates, it will serve as a tie-breaker. */</span> <span class="token keyword">void</span> <span class="token function">setPrimary</span><span class="token punctuation">(</span><span class="token keyword">boolean</span> primary<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return the constructor argument values for this bean. * <p>The returned instance can be modified during bean factory post-processing. * @return the ConstructorArgumentValues object (never {@code null}) */</span> <span class="token class-name">ConstructorArgumentValues</span> <span class="token function">getConstructorArgumentValues</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return the property values to be applied to a new instance of the bean. * <p>The returned instance can be modified during bean factory post-processing. * @return the MutablePropertyValues object (never {@code null}) */</span> <span class="token class-name">MutablePropertyValues</span> <span class="token function">getPropertyValues</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return whether this a <b>Singleton</b>, with a single, shared instance * returned on all calls. * @see #SCOPE_SINGLETON */</span> <span class="token keyword">boolean</span> <span class="token function">isSingleton</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return whether this a <b>Prototype</b>, with an independent instance * returned for each call. * @see #SCOPE_PROTOTYPE */</span> <span class="token keyword">boolean</span> <span class="token function">isPrototype</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return whether this bean is "abstract", that is, not meant to be instantiated. */</span> <span class="token keyword">boolean</span> <span class="token function">isAbstract</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Get the role hint for this {@code BeanDefinition}. The role hint * provides tools with an indication of the importance of a particular * {@code BeanDefinition}. * @see #ROLE_APPLICATION * @see #ROLE_INFRASTRUCTURE * @see #ROLE_SUPPORT */</span> <span class="token keyword">int</span> <span class="token function">getRole</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return a human-readable description of this bean definition. */</span> <span class="token class-name">String</span> <span class="token function">getDescription</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return a description of the resource that this bean definition * came from (for the purpose of showing context in case of errors). */</span> <span class="token class-name">String</span> <span class="token function">getResourceDescription</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">/** * Return the originating BeanDefinition, or {@code null} if none. * Allows for retrieving the decorated bean definition, if any. * <p>Note that this method returns the immediate originator. Iterate through the * originator chain to find the original BeanDefinition as defined by the user. */</span> <span class="token class-name">BeanDefinition</span> <span class="token function">getOriginatingBeanDefinition</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
}
大家仔细看看，是不是其实和我们定义的 class 差不多呢，主要都是一些 get/set 方法。里面的字段呢，下一讲我们详细讲解一下，会结合一些融会贯通的地方。
bean definition 接口的实现有哪些#
然后我们看看这个接口有哪些实现吧？
可以看到，这里有两个是我标红了，因为他们特殊，特殊在他们不属于 spring-beans 包，而是在 spring-context 包里。后边遇到了我们再单说，这里存疑。
再来看看这个接口的继承图：
可以获取注解信息的子接口 AnnotatedBeanDefinition#
我们看到，这个接口有一个子接口，是AnnotatedBeanDefinition。这个接口定义如下：
/** * Extended {@link org.springframework.beans.factory.config.BeanDefinition} * interface that exposes {@link org.springframework.core.type.AnnotationMetadata} * about its bean class - without requiring the class to be loaded yet. * 这个接口扩展了 BeanDefinition，可以获得 bean definition 中的 bean class 上的注解元数据。 * 举个例子，假设我们用 @controller 标注了某个类，那这里就能获取到 @controller 这个注解里面的信息 * * @author Juergen Hoeller * @since 2.5 * @see AnnotatedGenericBeanDefinition * @see org.springframework.core.type.AnnotationMetadata */ public interface AnnotatedBeanDefinition extends BeanDefinition {<span class="token comment">/** * Obtain the annotation metadata (as well as basic class metadata) * for this bean definition's bean class. * @return the annotation metadata object (never {@code null}) */</span> <span class="token class-name">AnnotationMetadata</span> <span class="token function">getMetadata</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
}
可以想一想有什么用，这个接口能取到 bean definition 中对应 bean class 上标注的注解元数据。
比如下面的 controller 举例：
@Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Component public @interface Controller {<span class="token comment">/** * The value may indicate a suggestion for a logical component name, * to be turned into a Spring bean in case of an autodetected component. * @return the suggested component name, if any */</span> <span class="token class-name">String</span> <span class="token function">value</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">default</span> <span class="token string">""</span><span class="token punctuation">;</span>
}
那这个AnnotatedBeanDefinition就能取到 controller 中的 value 字段的值。
我这里也写了个简单的例子，如下：
@Component("testService") public class HelloWorldService {
}
@Autowired
private ApplicationContext applicationContext;
@Override
public void run(String... args) {
DefaultListableBeanFactory beanFactory =
(DefaultListableBeanFactory) applicationContext.getAutowireCapableBeanFactory();
// 获取 bean definition，然后获取其注解元数据
AnnotatedBeanDefinition annotatedBeanDefinition = (AnnotatedBeanDefinition) beanFactory.getBeanDefinition("testService");
AnnotationMetadata metadata = annotatedBeanDefinition.getMetadata();
Map<String, Object> annotationAttributes = metadata.getAnnotationAttributes("org.springframework.stereotype.Component");
log.info("annotationAttributes:{}",annotationAttributes);
}
我这边打印出来就是：
信息: annotationAttributes:
代码在
接口下的实现类#
仔细看了两个接口 AnnotatedBeanDefinition和BeanDefinition，其实实现类都是差不多那几个。
基本上org.springframework.beans.factory.support.AbstractBeanDefinition充当了基本的实现，基本上，该实现的方法都实现了，除了一个：
/**
* Clone this bean definition.
* To be implemented by concrete subclasses.
* @return the cloned bean definition object
*/
public abstract AbstractBeanDefinition cloneBeanDefinition();
赶紧这个方法，对我们分析也没多大帮助，暂时跳过即可。
再看看org.springframework.beans.factory.support.GenericBeanDefinition，感觉很重要，我们看看：
public class GenericBeanDefinition extends AbstractBeanDefinition {<span class="token keyword">private</span> <span class="token class-name">String</span> parentName<span class="token punctuation">;</span> <span class="token comment">/** * 这里有点意思，类似于builder模式，先生成一个实例，再自己各种set方法设置相关属性 * * Create a new GenericBeanDefinition, to be configured through its bean * properties and configuration methods. * @see #setBeanClass * @see #setBeanClassName * @see #setScope * @see #setAutowireMode * @see #setDependencyCheck * @see #setConstructorArgumentValues * @see #setPropertyValues */</span> <span class="token keyword">public</span> <span class="token class-name">GenericBeanDefinition</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">super</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token annotation punctuation">@Override</span> <span class="token keyword">public</span> <span class="token class-name">AbstractBeanDefinition</span> <span class="token function">cloneBeanDefinition</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">GenericBeanDefinition</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span>
}
ok，都这么简单的话，就再看两个，spring beans 包中的org.springframework.beans.factory.annotation.AnnotatedGenericBeanDefinition:
public class AnnotatedGenericBeanDefinition extends GenericBeanDefinition implements AnnotatedBeanDefinition {<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">AnnotationMetadata</span> metadata<span class="token punctuation">;</span> <span class="token comment">/** * Create a new AnnotatedGenericBeanDefinition for the given bean class. * @param beanClass the loaded bean class */</span> <span class="token keyword">public</span> <span class="token class-name">AnnotatedGenericBeanDefinition</span><span class="token punctuation">(</span><span class="token class-name">Class</span><span class="token generics"><span class="token punctuation"><</span><span class="token operator">?</span><span class="token punctuation">></span></span> beanClass<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token function">setBeanClass</span><span class="token punctuation">(</span>beanClass<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>metadata <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">StandardAnnotationMetadata</span><span class="token punctuation">(</span>beanClass<span class="token punctuation">,</span> <span class="token boolean">true</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token comment">/** * Create a new AnnotatedGenericBeanDefinition for the given annotation metadata, * allowing for ASM-based processing and avoidance of early loading of the bean class. * Note that this constructor is functionally equivalent to * {@link org.springframework.context.annotation.ScannedGenericBeanDefinition * ScannedGenericBeanDefinition}, however the semantics of the latter indicate that * a bean was discovered specifically via component-scanning as opposed to other * means. * @param metadata the annotation metadata for the bean class in question * @since 3.1.1 */</span> <span class="token keyword">public</span> <span class="token class-name">AnnotatedGenericBeanDefinition</span><span class="token punctuation">(</span><span class="token class-name">AnnotationMetadata</span> metadata<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token class-name">Assert</span><span class="token punctuation">.</span><span class="token function">notNull</span><span class="token punctuation">(</span>metadata<span class="token punctuation">,</span> <span class="token string">"AnnotationMetadata must not be null"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token function">setBeanClassName</span><span class="token punctuation">(</span>metadata<span class="token punctuation">.</span><span class="token function">getClassName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>metadata <span class="token operator">=</span> metadata<span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token class-name">AnnotationMetadata</span> <span class="token function">getMetadata</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>metadata<span class="token punctuation">;</span> <span class="token punctuation">}</span>
}
很简单，就是多了获取 bean class 的注解的功能。
再看这个呢，
/** * Extension of the {@link GenericBeanDefinition} * class, based on an ASM ClassReader, with support for annotation metadata exposed * through the {@link AnnotatedBeanDefinition} interface. * * <p>This class does <i>not</i> load the bean {@code Class} early. * It rather retrieves all relevant metadata from the ".class" file itself, * parsed with the ASM ClassReader. It is functionally equivalent to * {@link AnnotatedGenericBeanDefinition#AnnotatedGenericBeanDefinition(AnnotationMetadata)} * but distinguishes by type beans that have been <em>scanned</em> vs those that have * been otherwise registered or detected by other means. * * @author Juergen Hoeller * @author Chris Beams * @since 2.5 * @see #getMetadata()* @see #getBeanClassName() * @see org.springframework.core.type.classreading.MetadataReaderFactory * @see AnnotatedGenericBeanDefinition */ @SuppressWarnings("serial") public class ScannedGenericBeanDefinition extends GenericBeanDefinition implements AnnotatedBeanDefinition {<span class="token keyword">private</span> <span class="token keyword">final</span> <span class="token class-name">AnnotationMetadata</span> metadata<span class="token punctuation">;</span> <span class="token comment">/** * Create a new ScannedGenericBeanDefinition for the class that the * given MetadataReader describes. * @param metadataReader the MetadataReader for the scanned target class */</span> <span class="token keyword">public</span> <span class="token class-name">ScannedGenericBeanDefinition</span><span class="token punctuation">(</span><span class="token class-name">MetadataReader</span> metadataReader<span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token class-name">Assert</span><span class="token punctuation">.</span><span class="token function">notNull</span><span class="token punctuation">(</span>metadataReader<span class="token punctuation">,</span> <span class="token string">"MetadataReader must not be null"</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token keyword">this</span><span class="token punctuation">.</span>metadata <span class="token operator">=</span> metadataReader<span class="token punctuation">.</span><span class="token function">getAnnotationMetadata</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token function">setBeanClassName</span><span class="token punctuation">(</span><span class="token keyword">this</span><span class="token punctuation">.</span>metadata<span class="token punctuation">.</span><span class="token function">getClassName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span> <span class="token keyword">public</span> <span class="token keyword">final</span> <span class="token class-name">AnnotationMetadata</span> <span class="token function">getMetadata</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> <span class="token keyword">return</span> <span class="token keyword">this</span><span class="token punctuation">.</span>metadata<span class="token punctuation">;</span> <span class="token punctuation">}</span>
}
我一开始，一眼看过去，感觉眼花了，差不多啊，但这个是在 spring context 包里，然后，可以看上面的注释，说是使用 asm 去获取注解信息。所以，这个和上面那个的差别是：
org.springframework.context.annotation.ScannedGenericBeanDefinition 位于 spring-context，使用 asm
org.springframework.beans.factory.annotation.AnnotatedGenericBeanDefinition 位于 spring-beans，使用反射
再看看org.springframework.beans.factory.support.RootBeanDefinition(位于 spring-beans)，这个类下面只有一个子类，位于 spring-context 的
org.springframework.context.annotation.ConfigurationClassBeanDefinitionReader.ConfigurationClassBeanDefinition
这两个类，一看就比较特别，能看出来，和 @configuration 注解有莫大关系，这个我们放后面讲。
总结#
本篇就先到这里，留了一些问题，放到后面（有些我也要查一下，哈哈）。下一讲继续。