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