以接口肢解bean factory，源码没那么神秘

本来昨天在看 spring frame的八股， 看到了IOC部分，但是实在看不懂是什么东西，讲是讲源码部分，但又不完全讲，我想着那我要不自己看一下源码

这是我画的Bean Factory的大致关系图

删去了bean别名管理接口（AliasRegistry）和bean定义接口（BeanDefinitionRegistry）避免复杂理解

BeanFactory有三个子类ListableBeanFactory ，HierarchicalBeanFactory，ConfigurableBeanFactory ，AutowireCapableBeanFactory 。

我们先来看看BeanFactory 只实现了IOC 容器的基本行为规范，好比是让需求方提出对目标的需求。

public interface BeanFactory {
//与FactoryBean创建的bean区分开来, 若命名的bean是FactoryBean，
//则获取将返回Factory，而不是Factory返回的实例。
    String FACTORY_BEAN_PREFIX = "&";

    Object getBean(String var1) throws BeansException;

    <T> T getBean(String var1, Class<T> var2) throws BeansException;

    Object getBean(String var1, Object... var2) throws BeansException;

    <T> T getBean(Class<T> var1) throws BeansException;

    <T> T getBean(Class<T> var1, Object... var2) throws BeansException;

    <T> ObjectProvider<T> getBeanProvider(Class<T> var1);

    <T> ObjectProvider<T> getBeanProvider(ResolvableType var1);

    boolean containsBean(String var1);

    boolean isSingleton(String var1) throws NoSuchBeanDefinitionException;

    boolean isPrototype(String var1) throws NoSuchBeanDefinitionException;

    boolean isTypeMatch(String var1, ResolvableType var2) throws NoSuchBeanDefinitionException;

    boolean isTypeMatch(String var1, Class<?> var2) throws NoSuchBeanDefinitionException;

    @Nullable
    Class<?> getType(String var1) throws NoSuchBeanDefinitionException;

    @Nullable
    Class<?> getType(String var1, boolean var2) throws NoSuchBeanDefinitionException;

    String[] getAliases(String var1);
}

ListableBeanFactory 定义了Factory Bean的可枚举性，适用于批量操作 bean 的场景

public interface ListableBeanFactory extends BeanFactory {
    boolean containsBeanDefinition(String var1);

    int getBeanDefinitionCount();

    String[] getBeanDefinitionNames();

    <T> ObjectProvider<T> getBeanProvider(Class<T> var1, boolean var2);

    <T> ObjectProvider<T> getBeanProvider(ResolvableType var1, boolean var2);

    String[] getBeanNamesForType(ResolvableType var1);

    String[] getBeanNamesForType(ResolvableType var1, boolean var2, boolean var3);

    String[] getBeanNamesForType(@Nullable Class<?> var1);

    String[] getBeanNamesForType(@Nullable Class<?> var1, boolean var2, boolean var3);

    <T> Map<String, T> getBeansOfType(@Nullable Class<T> var1) throws BeansException;

    <T> Map<String, T> getBeansOfType(@Nullable Class<T> var1, boolean var2, boolean var3) throws BeansException;

    String[] getBeanNamesForAnnotation(Class<? extends Annotation> var1);

    Map<String, Object> getBeansWithAnnotation(Class<? extends Annotation> var1) throws BeansException;

    @Nullable
    <A extends Annotation> A findAnnotationOnBean(String var1, Class<A> var2) throws NoSuchBeanDefinitionException;

    @Nullable
    <A extends Annotation> A findAnnotationOnBean(String var1, Class<A> var2, boolean var3) throws NoSuchBeanDefinitionException;
}

HierarchicalBeanFactory 定义了Bean Factory的分层能力

之前还不知道Bean Factory可以有父子容器区分

Spring MVC 有以下分层

• 根上下文（ContextLoaderListener 或 Spring Boot 创建）作为父容器。

如服务层、数据访问层和基础设施 bean（DataSource）。

• DispatcherServlet 的上下文作为子容器。

定义 Web 层特定 bean，如控制器、HandlerMapping 等。

public interface HierarchicalBeanFactory extends BeanFactory {
    @Nullable
    BeanFactory getParentBeanFactory();

    boolean containsLocalBean(String var1);
}

ConfigurableBeanFactory 定义了自定义Bean工厂的能力 ， 自定义类加载器、beany定义、作用域、依赖关系。

public interface ConfigurableBeanFactory extends HierarchicalBeanFactory, SingletonBeanRegistry {
    // 自定义类加载器
    void setBeanClassLoader(@Nullable ClassLoader var1);
    @Nullable
    ClassLoader getBeanClassLoader();
    void setTempClassLoader(@Nullable ClassLoader var1);
    @Nullable
    ClassLoader getTempClassLoader();

    // bean 定义
    void setCacheBeanMetadata(boolean var1);
    boolean isCacheBeanMetadata();
    BeanDefinition getMergedBeanDefinition(String var1) throws NoSuchBeanDefinitionException;
    boolean isFactoryBean(String var1) throws NoSuchBeanDefinitionException;

    // 作用域
    void registerScope(String var1, Scope var2);
    String[] getRegisteredScopeNames();
    @Nullable
    Scope getRegisteredScope(String var1);

    // 依赖关系
    void registerDependentBean(String var1, String var2);
    String[] getDependentBeans(String var1);
    String[] getDependenciesForBean(String var1);

    ......
    ......
}

AutowireCapableBeanFactory 实现了Bean自动装配能力

public interface AutowireCapableBeanFactory extends BeanFactory {
    int AUTOWIRE_NO = 0;
    int AUTOWIRE_BY_NAME = 1;
    int AUTOWIRE_BY_TYPE = 2;
    int AUTOWIRE_CONSTRUCTOR = 3;
    /** @deprecated */
    @Deprecated
    int AUTOWIRE_AUTODETECT = 4;
    String ORIGINAL_INSTANCE_SUFFIX = ".ORIGINAL";

    <T> T createBean(Class<T> var1) throws BeansException;

    void autowireBean(Object var1) throws BeansException;

    Object configureBean(Object var1, String var2) throws BeansException;

    Object createBean(Class<?> var1, int var2, boolean var3) throws BeansException;

    Object autowire(Class<?> var1, int var2, boolean var3) throws BeansException;

    void autowireBeanProperties(Object var1, int var2, boolean var3) throws BeansException;

    void applyBeanPropertyValues(Object var1, String var2) throws BeansException;

    Object initializeBean(Object var1, String var2) throws BeansException;

    Object applyBeanPostProcessorsBeforeInitialization(Object var1, String var2) throws BeansException;

    Object applyBeanPostProcessorsAfterInitialization(Object var1, String var2) throws BeansException;

    void destroyBean(Object var1);

    <T> NamedBeanHolder<T> resolveNamedBean(Class<T> var1) throws BeansException;

    Object resolveBeanByName(String var1, DependencyDescriptor var2) throws BeansException;

    @Nullable
    Object resolveDependency(DependencyDescriptor var1, @Nullable String var2) throws BeansException;

    @Nullable
    Object resolveDependency(DependencyDescriptor var1, @Nullable String var2, @Nullable Set<String> var3, @Nullable TypeConverter var4) throws BeansException;
}

看完了这些接口类和接口方法，对IOC容器有了更扩展一些的理解

其实源码还是挺容易看的，先通过一个类向上找到基类，再往下看详细的接口类，实现类。 对其有一个全局的理解