答：用来访问Spring bean容器的根接口
里面主要是一些getBean的抽象方法、getType啊、containBean啊、isSingleton啊等等
子类DefaultListableBeanFactory是spring框架里面代码使用的BeanFactory实现。
扩展：BeanFactory接口的代码
public interface BeanFactory { /** * Used to dereference a {@link FactoryBean} instance and distinguish it from * beans <i>created</i> by the FactoryBean. For example, if the bean named * {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject} * will return the factory, not the instance returned by the factory. */ String FACTORY_BEAN_PREFIX = "&"; /** * Return an instance, which may be shared or independent, of the specified bean. * <p>This method allows a Spring BeanFactory to be used as a replacement for the * Singleton or Prototype design pattern. Callers may retain references to * returned objects in the case of Singleton beans. * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to retrieve * @return an instance of the bean * @throws NoSuchBeanDefinitionException if there is no bean with the specified name * @throws BeansException if the bean could not be obtained */ Object getBean(String name) throws BeansException; /** * Return an instance, which may be shared or independent, of the specified bean. * <p>Behaves the same as {@link #getBean(String)}, but provides a measure of type * safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the * required type. This means that ClassCastException can't be thrown on casting * the result correctly, as can happen with {@link #getBean(String)}. * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to retrieve * @param requiredType type the bean must match; can be an interface or superclass * @return an instance of the bean * @throws NoSuchBeanDefinitionException if there is no such bean definition * @throws BeanNotOfRequiredTypeException if the bean is not of the required type * @throws BeansException if the bean could not be created */ <T> T getBean(String name, Class<T> requiredType) throws BeansException; /** * Return an instance, which may be shared or independent, of the specified bean. * <p>Allows for specifying explicit constructor arguments / factory method arguments, * overriding the specified default arguments (if any) in the bean definition. * @param name the name of the bean to retrieve * @param args arguments to use when creating a bean instance using explicit arguments * (only applied when creating a new instance as opposed to retrieving an existing one) * @return an instance of the bean * @throws NoSuchBeanDefinitionException if there is no such bean definition * @throws BeanDefinitionStoreException if arguments have been given but * the affected bean isn't a prototype * @throws BeansException if the bean could not be created * @since 2.5 */ Object getBean(String name, Object... args) throws BeansException; /** * Return the bean instance that uniquely matches the given object type, if any. * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory * but may also be translated into a conventional by-name lookup based on the name * of the given type. For more extensive retrieval operations across sets of beans, * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}. * @param requiredType type the bean must match; can be an interface or superclass * @return an instance of the single bean matching the required type * @throws NoSuchBeanDefinitionException if no bean of the given type was found * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found * @throws BeansException if the bean could not be created * @since 3.0 * @see ListableBeanFactory */ <T> T getBean(Class<T> requiredType) throws BeansException; /** * Return an instance, which may be shared or independent, of the specified bean. * <p>Allows for specifying explicit constructor arguments / factory method arguments, * overriding the specified default arguments (if any) in the bean definition. * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory * but may also be translated into a conventional by-name lookup based on the name * of the given type. For more extensive retrieval operations across sets of beans, * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}. * @param requiredType type the bean must match; can be an interface or superclass * @param args arguments to use when creating a bean instance using explicit arguments * (only applied when creating a new instance as opposed to retrieving an existing one) * @return an instance of the bean * @throws NoSuchBeanDefinitionException if there is no such bean definition * @throws BeanDefinitionStoreException if arguments have been given but * the affected bean isn't a prototype * @throws BeansException if the bean could not be created * @since 4.1 */ <T> T getBean(Class<T> requiredType, Object... args) throws BeansException; /** * Return a provider for the specified bean, allowing for lazy on-demand retrieval * of instances, including availability and uniqueness options. * @param requiredType type the bean must match; can be an interface or superclass * @return a corresponding provider handle * @since 5.1 * @see #getBeanProvider(ResolvableType) */ <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType); /** * Return a provider for the specified bean, allowing for lazy on-demand retrieval * of instances, including availability and uniqueness options. * @param requiredType type the bean must match; can be a generic type declaration. * Note that collection types are not supported here, in contrast to reflective * injection points. For programmatically retrieving a list of beans matching a * specific type, specify the actual bean type as an argument here and subsequently * use {@link ObjectProvider#orderedStream()} or its lazy streaming/iteration options. * @return a corresponding provider handle * @since 5.1 * @see ObjectProvider#iterator() * @see ObjectProvider#stream() * @see ObjectProvider#orderedStream() */ <T> ObjectProvider<T> getBeanProvider(ResolvableType requiredType); /** * Does this bean factory contain a bean definition or externally registered singleton * instance with the given name? * <p>If the given name is an alias, it will be translated back to the corresponding * canonical bean name. * <p>If this factory is hierarchical, will ask any parent factory if the bean cannot * be found in this factory instance. * <p>If a bean definition or singleton instance matching the given name is found, * this method will return {@code true} whether the named bean definition is concrete * or abstract, lazy or eager, in scope or not. Therefore, note that a {@code true} * return value from this method does not necessarily indicate that {@link #getBean} * will be able to obtain an instance for the same name. * @param name the name of the bean to query * @return whether a bean with the given name is present */ boolean containsBean(String name); /** * Is this bean a shared singleton? That is, will {@link #getBean} always * return the same instance? * <p>Note: This method returning {@code false} does not clearly indicate * independent instances. It indicates non-singleton instances, which may correspond * to a scoped bean as well. Use the {@link #isPrototype} operation to explicitly * check for independent instances. * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to query * @return whether this bean corresponds to a singleton instance * @throws NoSuchBeanDefinitionException if there is no bean with the given name * @see #getBean * @see #isPrototype */ boolean isSingleton(String name) throws NoSuchBeanDefinitionException; /** * Is this bean a prototype? That is, will {@link #getBean} always return * independent instances? * <p>Note: This method returning {@code false} does not clearly indicate * a singleton object. It indicates non-independent instances, which may correspond * to a scoped bean as well. Use the {@link #isSingleton} operation to explicitly * check for a shared singleton instance. * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to query * @return whether this bean will always deliver independent instances * @throws NoSuchBeanDefinitionException if there is no bean with the given name * @since 2.0.3 * @see #getBean * @see #isSingleton */ boolean isPrototype(String name) throws NoSuchBeanDefinitionException; /** * Check whether the bean with the given name matches the specified type. * More specifically, check whether a {@link #getBean} call for the given name * would return an object that is assignable to the specified target type. * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to query * @param typeToMatch the type to match against (as a {@code ResolvableType}) * @return {@code true} if the bean type matches, * {@code false} if it doesn't match or cannot be determined yet * @throws NoSuchBeanDefinitionException if there is no bean with the given name * @since 4.2 * @see #getBean * @see #getType */ boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException; /** * Check whether the bean with the given name matches the specified type. * More specifically, check whether a {@link #getBean} call for the given name * would return an object that is assignable to the specified target type. * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to query * @param typeToMatch the type to match against (as a {@code Class}) * @return {@code true} if the bean type matches, * {@code false} if it doesn't match or cannot be determined yet * @throws NoSuchBeanDefinitionException if there is no bean with the given name * @since 2.0.1 * @see #getBean * @see #getType */ boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException; /** * Determine the type of the bean with the given name. More specifically, * determine the type of object that {@link #getBean} would return for the given name. * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates, * as exposed by {@link FactoryBean#getObjectType()}. This may lead to the initialization * of a previously uninitialized {@code FactoryBean} (see {@link #getType(String, boolean)}). * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to query * @return the type of the bean, or {@code null} if not determinable * @throws NoSuchBeanDefinitionException if there is no bean with the given name * @since 1.1.2 * @see #getBean * @see #isTypeMatch */ @Nullable Class<?> getType(String name) throws NoSuchBeanDefinitionException; /** * Determine the type of the bean with the given name. More specifically, * determine the type of object that {@link #getBean} would return for the given name. * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates, * as exposed by {@link FactoryBean#getObjectType()}. Depending on the * {@code allowFactoryBeanInit} flag, this may lead to the initialization of a previously * uninitialized {@code FactoryBean} if no early type information is available. * <p>Translates aliases back to the corresponding canonical bean name. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the name of the bean to query * @param allowFactoryBeanInit whether a {@code FactoryBean} may get initialized * just for the purpose of determining its object type * @return the type of the bean, or {@code null} if not determinable * @throws NoSuchBeanDefinitionException if there is no bean with the given name * @since 5.2 * @see #getBean * @see #isTypeMatch */ @Nullable Class<?> getType(String name, boolean allowFactoryBeanInit) throws NoSuchBeanDefinitionException; /** * Return the aliases for the given bean name, if any. * <p>All of those aliases point to the same bean when used in a {@link #getBean} call. * <p>If the given name is an alias, the corresponding original bean name * and other aliases (if any) will be returned, with the original bean name * being the first element in the array. * <p>Will ask the parent factory if the bean cannot be found in this factory instance. * @param name the bean name to check for aliases * @return the aliases, or an empty array if none * @see #getBean */ String[] getAliases(String name); }