spring 基于注解启动
主要有两个class实现注解启动
- annotationconfigapplicationcontext
- annotationconfigwebapplicationcontext
我们以annotationconfigapplicationcontext 为研究对象
annotationconfigapplicationcontext.png
引入spring 最小依赖
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<dependency> <groupid>org.springframework</groupid> <artifactid>spring-context</artifactid> <version>${spring.version}</version></dependency> |
编写器启动代码
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public static void main(string[] args) {annotationconfigapplicationcontext applicationcontext = new annotationconfigapplicationcontext();applicationcontext.register(beanconfig.class);applicationcontext.refresh();date date = applicationcontext.getbean("date",date.class);system.out.println(date);} |
annotationconfigapplicationcontext 构造函数
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public annotationconfigapplicationcontext() { //负责注册class ，读取器 this.reader = new annotatedbeandefinitionreader(this); //负责扫描指定类路径下的class，注册bean this.scanner = new classpathbeandefinitionscanner(this);} |
annotatedbeandefinitionreader 构造方法
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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; //初始化conditionevaluator this.conditionevaluator = new conditionevaluator(registry, environment, null); /** 在給定的注册表中註冊所有相关的post processors * 判断容器是否已经存在给定注册表的bean，如果没有注册bean，并将bean放入容器中 * 把所有的处理处理器列出来 * configurationclasspostprocessor 內部管理的配置注解处理器 * autowiredannotationbeanpostprocessor 内部管理@autowired 的处理器 * requiredannotationbeanpostprocessor @required的处理器 * commonannotationbeanpostprocessor jsr-250注解处理器 ，先判断是否支持jsr，如果支持注册 * persistenceannotationbeanpostprocessor jpa管理 先使用类加载器查找是否存在，如果有这个包则注册 * eventlistenermethodprocessor @eventlistener的处理器 * defaulteventlistenerfactory 管理eventlistenerfactory处理器 */ annotationconfigutils.registerannotationconfigprocessors(this.registry);} |
conditionevaluator 这个对象干什么,点击进去
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public conditionevaluator(@nullable beandefinitionregistry registry, @nullable environment environment, @nullable resourceloader resourceloader) { this.context = new conditioncontextimpl(registry, environment, resourceloader); } //conditioncontextimpl 实现了conditioncontext接口，conditionevaluator静态内部类 public conditioncontextimpl(@nullable beandefinitionregistry registry, @nullable environment environment, @nullable resourceloader resourceloader) { this.registry = registry; this.beanfactory = deducebeanfactory(registry); this.environment = (environment != null ? environment : deduceenvironment(registry)); this.resourceloader = (resourceloader != null ? resourceloader : deduceresourceloader(registry)); this.classloader = deduceclassloader(resourceloader, this.beanfactory); } |
可以知道conditionevaluator使用外部传参的方法初始化了spring容器顶级对象
beanfactory,environment,resourceloader,classloader。在将这些传给conditioncontextimpl为接下来的解析@conditional注解做好准备
classpathbeandefinitionscanner构造函数
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public classpathbeandefinitionscanner(beandefinitionregistry registry) { this(registry, true);}public classpathbeandefinitionscanner(beandefinitionregistry registry, boolean usedefaultfilters) { this(registry, usedefaultfilters, getorcreateenvironment(registry));}public classpathbeandefinitionscanner(beandefinitionregistry registry, boolean usedefaultfilters, environment environment) { this(registry, usedefaultfilters, environment, (registry instanceof resourceloader ? (resourceloader) registry : null));}public classpathbeandefinitionscanner(beandefinitionregistry registry, boolean usedefaultfilters, environment environment, @nullable resourceloader resourceloader) { assert.notnull(registry, "beandefinitionregistry must not be null"); this.registry = registry; if (usedefaultfilters) { registerdefaultfilters(); } setenvironment(environment); setresourceloader(resourceloader);}protected void registerdefaultfilters() { this.includefilters.add(new annotationtypefilter(component.class)); classloader cl = classpathscanningcandidatecomponentprovider.class.getclassloader(); try { this.includefilters.add(new annotationtypefilter( ((class<? extends annotation>) classutils.forname("javax.annotation.managedbean", cl)), false)); logger.debug("jsr-250 'javax.annotation.managedbean' found and supported for component scanning"); } catch (classnotfoundexception ex) { } try { this.includefilters.add(new annotationtypefilter( ((class<? extends annotation>) classutils.forname("javax.inject.named", cl)), false)); logger.debug("jsr-330 'javax.inject.named' annotation found and supported for component scanning"); } catch (classnotfoundexception ex) { // jsr-330 api not available - simply skip. }} |
绕了地球几圈了，其实就是将spring 顶级接口 environment,resourceloader赋值，使用默认注解过滤器，首先将@component加入list中，判断当前环境是否支持jsr-250，jsr-330，相应加入过滤器中。也就是这个扫描器默认只扫描@component或者jsr-250，jsr-330的标记的class。
applicationcontext.register(beanconfig.class)
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public void register(class<?>... annotatedclasses) { assert.notempty(annotatedclasses, "at least one annotated class must be specified"); this.reader.register(annotatedclasses); //调用 刚刚初始化读取器 } |============================annotatedbeandefinitionreader 读取器代码====================================================================================================== public void register(class<?>... annotatedclasses) { for (class<?> annotatedclass : annotatedclasses) { registerbean(annotatedclass); } } public void registerbean(class<?> annotatedclass) { doregisterbean(annotatedclass, null, null, null); } /** *从给定的bean解析class给定的注解，执行相应的初始化，保存到spring容器中 */ <t> void doregisterbean(class<t> annotatedclass, @nullable supplier<t> instancesupplier, @nullable string name, @nullable class<? extends annotation>[] qualifiers, beandefinitioncustomizer... definitioncustomizers) { //根据class的annotated 得出元数据 annotationmetadata annotatedgenericbeandefinition abd = new annotatedgenericbeandefinition(annotatedclass); /** * 判断注册的class 是否包含@conditional注解，如果有获取全部value，放入list中 * 排序后，遍历所有的conditiion的实现，使用反射获取对象，执行matches方法， * 如果发现有返回false，中断循环直接返回true， */ if (this.conditionevaluator.shouldskip(abd.getmetadata())) { //如果 @conditional条件不满足，不进行注册 return; } abd.setinstancesupplier(instancesupplier); //解析class是否有@scope,解析@scope注解返回scopemetadata对象，没有直接返回空 scopemetadata scopemetadata = this.scopemetadataresolver.resolvescopemetadata(abd); abd.setscope(scopemetadata.getscopename()); //判断注解上value是否有值，有就使用这个作为beanname，没有则取类名 string beanname = (name != null ? name : this.beannamegenerator.generatebeanname(abd, this.registry)); //继续解析annotationmetadata的@lazy,@primary，@dependson，@role，@description的注解，放入结果放入对象的属性中 annotationconfigutils.processcommondefinitionannotations(abd); //这个类只是beandefinition 包装类 beandefinitionholder definitionholder = new beandefinitionholder(abd, beanname); //是否需要代理类，如果是则修改内部属性，重新生成beandefinition 对象 definitionholder = annotationconfigutils.applyscopedproxymode(scopemetadata, definitionholder, this.registry); //调用defaultlistablebeanfactory.registerbeandefinition的方法，做一些安全性校验再，将definitionholder 放入register容器中 beandefinitionreaderutils.registerbeandefinition(definitionholder, this.registry); } |
这个方法就是将注册的bean，解析class上的注解，初始化注解数据，做相应处理，转化成beandefinition ,放入spring 容器中保存起来。
我们看下beandefinition是怎么实现注册到spring的容器中，主要由defaultlistablebeanfactory.registerbeandefinition来实现
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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 { //对beandefinition 进行校验判断methodoverrides不能为空，必须拥有工厂方法 ((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) { //这个方法是判断是否允许出现重名bean，并且是不同的定义bean，是否可以覆盖前者 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 { //调用alreadycreated.isempty()，alreadycreated set对象，保存已经创建beanname //文档中表示created，跟这里注册应该不是同一个行为，这个要看到后面才知道什么意思 if (hasbeancreationstarted()) { synchronized (this.beandefinitionmap) {//更新数据 this.beandefinitionmap.put(beanname, beandefinition); list<string> updateddefinitions = new arraylist<>(this.beandefinitionnames.size() + 1); updateddefinitions.addall(this.beandefinitionnames); updateddefinitions.add(beanname); this.beandefinitionnames = updateddefinitions; if (this.manualsingletonnames.contains(beanname)) { set<string> updatedsingletons = new linkedhashset<>(this.manualsingletonnames); updatedsingletons.remove(beanname); this.manualsingletonnames = updatedsingletons; } } } else { //spring beandefinition 容器，一个map转载 this.beandefinitionmap.put(beanname, beandefinition); //保存beanname，主要用于记录每个bean注册顺序 this.beandefinitionnames.add(beanname); //删除单例，注册成一个普通bean this.manualsingletonnames.remove(beanname); } this.frozenbeandefinitionnames = null; } if (oldbeandefinition != null || containssingleton(beanname)) { //更新spring容器里beanname resetbeandefinition(beanname); } } |
将beandefinition注册到spring容器中，并没有太多复杂的逻辑，只是做一些安全性的检查。
beandefinition
一个beandefinition描述了一个bean的实例，包括属性值，构造方法参数值和继承自它的类的更多信息。beandefinition仅仅是一个最简单的接口，主要功能是允许beanfactorypostprocessor 例如propertyplaceholderconfigure 能够检索并修改属性值和别的bean的元数据（译注）
spring 容器beandefinition主要分为rootbeandefinition,annotatedgenericbeandefinition这两种
- rootbeandefinition spring factory中的特定bean
- annotatedgenericbeandefinition 用户自定义bean
spring 启动流程总结
annotationconfigapplicationcontext 初始化.png
这些beandefinition只是放入到spirng 容器中，并没有进行任何初始化对象的操作，真正的ioc操作都在refresh(),这个方法有空再进行分析。
总结
以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对服务器之家的支持。
原文链接：https://www.jianshu.com/p/573bdae020e9
