sping ioc 源码分析（一）-- register(componentClasses) 方法
一.测试环境的搭建：
public class Apple { }
@Component public class MyComponet { }
public class MyCondition implements Condition { @Override public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) { return metadata.isAnnotated("org.springframework.context.annotation.Configuration"); } } @Configuration @Import(Apple.class) public class MyConfig { @Bean public Student student(){ return new Student(); } } public class Student { } @Configuration @ComponentScan("com.yang.xiao.hui.ioc") @Conditional(MyCondition.class) public class App { public static void main( String[] args ) { ApplicationContext ctx = new AnnotationConfigApplicationContext(App.class); } }
//主要分析的是@import,@Componet@Bean @componentScan的方式向spring容器中注入bean的方式：
一个类变成bean的简单过程：
debug调试:
在创建一个类时，会先初始化其父类：GenericApplicationContext 断点在该类的构造器中：
父类创建的过程中，new 了一个beanFactory,而这个就是我们侠义上的ioc容器了，我们的bean定义信息和单例bean都是存在这里的：我们看看该类：
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable { @Nullable private static Class<?> javaxInjectProviderClass; static { try { javaxInjectProviderClass = ClassUtils.forName("javax.inject.Provider", DefaultListableBeanFactory.class.getClassLoader()); } catch (ClassNotFoundException ex) { // JSR-330 API not available - Provider interface simply not supported then. javaxInjectProviderClass = null; } } /** Map from serialized id to factory instance. */ private static final Map<String, Reference<DefaultListableBeanFactory>> serializableFactories = new ConcurrentHashMap<>(8); /** Optional id for this factory, for serialization purposes. */ @Nullable private String serializationId; /** Whether to allow re-registration of a different definition with the same name. */ private boolean allowBeanDefinitionOverriding = true; /** Whether to allow eager class loading even for lazy-init beans. */ private boolean allowEagerClassLoading = true; /** Optional OrderComparator for dependency Lists and arrays. */ @Nullable private Comparator<Object> dependencyComparator; /** Resolver to use for checking if a bean definition is an autowire candidate. */ private AutowireCandidateResolver autowireCandidateResolver = new SimpleAutowireCandidateResolver(); /** Map from dependency type to corresponding autowired value. */ private final Map<Class<?>, Object> resolvableDependencies = new ConcurrentHashMap<>(16); /** Map of bean definition objects, keyed by bean name. */ private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256); //这里存储了bean的名称和其定义信息 /** Map of singleton and non-singleton bean names, keyed by dependency type. */ private final Map<Class<?>, String[]> allBeanNamesByType = new ConcurrentHashMap<>(64); //bean的类型和对应的beanName,一个bean是可以有别名的 /** Map of singleton-only bean names, keyed by dependency type. */ private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<>(64); /** List of bean definition names, in registration order. */ private volatile List<String> beanDefinitionNames = new ArrayList<>(256);//以list集合的方式，存储了所有的beanName /** List of names of manually registered singletons, in registration order. */ private volatile Set<String> manualSingletonNames = new LinkedHashSet<>(16); //手动注册的单列的bean /** Cached array of bean definition names in case of frozen configuration. */ @Nullable private volatile String[] frozenBeanDefinitionNames; /** Whether bean definition metadata may be cached for all beans. */ private volatile boolean configurationFrozen = false;
//。。。。。。。。。。。。。。。。。。。。省略部分代码。。。。。。。。。。。。。。。。。。
}
由继承体系可知：DefaultListableBeanFactory 继承了DefaultSingletonBeanRegistry，因此我们看看这个类
小结：我们的bean定义信息和bean对象最终都会存到DefaultListableBeanFactory类对应的属性中：Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256) 和private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
我们继续debug调试：
//主要看看this.reader = new AnnotatedBeanDefinitionReader(this);
//该对象底层给beanFactory添加了几个核心的后置处理器
public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors( BeanDefinitionRegistry registry, @Nullable Object source) { DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry); //获取beanFactory if (beanFactory != null) { if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) { beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE); //设置一个用于排序的比较器 } if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) { beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver()); //设置一个用于解析@lazy @qualifier注解的解析器 } } Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<>(8); if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class); //设置一个解析配置类的后置处理器，这个是核心 def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class); //设置一个用于解析@autowired注解的后置处理器 def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)); } // Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor. if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class); //设置一个用于解析@preDestory 和@postConstruct注解的后置处理器 def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)); } // Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor. if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(); try { def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, AnnotationConfigUtils.class.getClassLoader())); } catch (ClassNotFoundException ex) { throw new IllegalStateException( "Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex); } def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class); //事件相关的后置处理器 def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME)); } if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) { RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class); //事件工厂 def.setSource(source); beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME)); } return beanDefs; }
//本次我们主要分析的方法： register(componentClasses);
<T> void doRegisterBean(Class<T> beanClass, @Nullable Supplier<T> instanceSupplier, @Nullable String name, @Nullable Class<? extends Annotation>[] qualifiers, BeanDefinitionCustomizer... definitionCustomizers) { AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass); //创建beanDefinition if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) { //这里是处理Condition注解，如果条件匹配就跳过，后续会分析 return; } abd.setInstanceSupplier(instanceSupplier);//设置实例工厂，这里为null ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd); //获取@scope注解的元信息，这个在aop源码博客有分析过 abd.setScope(scopeMetadata.getScopeName()); String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry)); AnnotationConfigUtils.processCommonDefinitionAnnotations(abd); //这里是处理bean的一些公共注解：@Lazy，@Primary，@DependsOn，@Role，@Description if (qualifiers != null) {//这里为null for (Class<? extends Annotation> qualifier : qualifiers) { //处理@Lazy，@Primary，@qualifier if (Primary.class == qualifier) { abd.setPrimary(true); } else if (Lazy.class == qualifier) { abd.setLazyInit(true); } else { abd.addQualifier(new AutowireCandidateQualifier(qualifier)); } } } for (BeanDefinitionCustomizer customizer : definitionCustomizers) { //这里也为null customizer.customize(abd); //允许我们对bean的定义信息做一些修改 } BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName); //装饰一下beanDefinition definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry); //处理bean的@Scope注解 BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);//向DefaultListableBeanFactory中注册beanDefinition,后面会跟进 }
@Override public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition) throws BeanDefinitionStoreException { BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);//判断是否已经存在对应的beanDifinition了 if (existingDefinition != null) { if (!isAllowBeanDefinitionOverriding()) { //如果已经存在，并且不允许覆盖就抛异常 throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition); } else if (existingDefinition.getRole() < beanDefinition.getRole()) { //角色升级，我们自己定义的bean,role就是application,spring自己的bean,角色就是role_support或者ROLE_INFRASTRUCTURE // e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE if (logger.isInfoEnabled()) { logger.info("Overriding user-defined bean definition for bean '" + beanName + "' with a framework-generated bean definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } else if (!beanDefinition.equals(existingDefinition)) {//如果跟之前的不一样，就打印一下日志 if (logger.isDebugEnabled()) { logger.debug("Overriding bean definition for bean '" + beanName + "' with a different definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } else { if (logger.isTraceEnabled()) { logger.trace("Overriding bean definition for bean '" + beanName + "' with an equivalent definition: replacing [" + existingDefinition + "] with [" + beanDefinition + "]"); } } this.beanDefinitionMap.put(beanName, beanDefinition); //将bean的定义信息存到map集合中 } else { if (hasBeanCreationStarted()) { //如果存在bean的创建已经开始 // Cannot modify startup-time collection elements anymore (for stable iteration) synchronized (this.beanDefinitionMap) { this.beanDefinitionMap.put(beanName, beanDefinition);//将bean的定义信息存到map集合中 List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1); updatedDefinitions.addAll(this.beanDefinitionNames); updatedDefinitions.add(beanName); this.beanDefinitionNames = updatedDefinitions; removeManualSingletonName(beanName); } } else { // Still in startup registration phase 还在注册阶段 this.beanDefinitionMap.put(beanName, beanDefinition);//将bean的定义信息存到map集合中 this.beanDefinitionNames.add(beanName); removeManualSingletonName(beanName); } this.frozenBeanDefinitionNames = null; } if (existingDefinition != null || containsSingleton(beanName)) { //bean的实例已经创建 resetBeanDefinition(beanName); //重新设置bean的定义信息 } }
接下来，我们回去看看condition注解的解析逻辑：
public boolean shouldSkip(@Nullable AnnotatedTypeMetadata metadata, @Nullable ConfigurationPhase phase) { if (metadata == null || !metadata.isAnnotated(Conditional.class.getName())) { //先判断有没conditional注解，我们在本次的测试中，添加了@Conditional(MyCondition.class) return false; } if (phase == null) { //ConfigurationPhase phase 是一个枚举，用于判断condition生效的阶段 if (metadata instanceof AnnotationMetadata && ConfigurationClassUtils.isConfigurationCandidate((AnnotationMetadata) metadata)) { //如果被Conditonal标注的类是一个是一个配置类 return shouldSkip(metadata, ConfigurationPhase.PARSE_CONFIGURATION); //再次递归调用本方法，此时枚举就有值了 } return shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN); } List<Condition> conditions = new ArrayList<>(); for (String[] conditionClasses : getConditionClasses(metadata)) { //获取所有的Conditional注解的属性值，业绩是Condition.class的实现类类名 for (String conditionClass : conditionClasses) { Condition condition = getCondition(conditionClass, this.context.getClassLoader());//反射创建Conditon.class的实例 conditions.add(condition); } } AnnotationAwareOrderComparator.sort(conditions); //排序 for (Condition condition : conditions) { ConfigurationPhase requiredPhase = null; if (condition instanceof ConfigurationCondition) { requiredPhase = ((ConfigurationCondition) condition).getConfigurationPhase(); }
//如果requiredPhase 为null,或者枚举值一致才会去匹配条件，如果条件匹配不上，就要跳过该bean,这个bean就不会加入到spring容器中 if ((requiredPhase == null || requiredPhase == phase) && !condition.matches(this.context, metadata)) { return true; } } return false; }
//小结： register(componentClasses); 方法的作用就是将主启动类的bean的定义信息注册到容器
