就Spring引导应用程序而言，bean只是一个Java对象，它是在应用程序启动时由Spring框架创建的。

对象的用途可以是任何东西——配置、服务、数据库连接工厂等等——Spring并不关心这些。

大多数bean依赖于其他bean才能工作，例如实体管理器可能需要一个数据库连接。Spring框架能够找出如何将bean自动连接在一起。从应用程序开发人员的角度来看，您只需声明所需的bean，它们就会“神奇地”出现在您的应用程序中，随时可以使用。

For a Java class to be usable as a Java bean, its setter- and getter-method names need to be as per the JavaBean guidelines (also called design patterns) for properties. If such a Java class is instantiable & manageable by the Spring IoC container, it is a Spring bean. To achieve this, the programmer wires the class as a bean definition of a suitable scope by using XML config files or annotations or a mix of both. The programmer can create new Spring beans out of existing Spring beans by wiring further by passing the latter to constructor-arguments of the former either as string-names as <idref> elements or by dependency injection (it can be recursive).

这个答案可以与我的这个SO答案一起阅读，以获得更多的背景信息。

就Spring引导应用程序而言，bean只是一个Java对象，它是在应用程序启动时由Spring框架创建的。

对象的用途可以是任何东西——配置、服务、数据库连接工厂等等——Spring并不关心这些。

大多数bean依赖于其他bean才能工作，例如实体管理器可能需要一个数据库连接。Spring框架能够找出如何将bean自动连接在一起。从应用程序开发人员的角度来看，您只需声明所需的bean，它们就会“神奇地”出现在您的应用程序中，随时可以使用。

你只理解了一部分。您必须根据需要定制bean，并通知Spring容器在需要时管理它，方法是使用Martin Fowler创造的通常称为IoC(控制反转)的方法，也称为依赖注入(DI)。

您以某种方式连接bean，这样您就不必关心实例化或计算bean上的任何依赖项。这就是众所周知的好莱坞原则。

谷歌是最好的工具，除了在这个问题中你会被淹没的链接之外，还可以探索更多关于这个问题的内容。：）

Spring beans are just object instances that are managed by the Spring IOC container. Spring IOC container carry the Bag of Bean.Bean creation,maintain and deletion are the responsibilities of Spring Container. We can put the bean in to Spring by Wiring and Auto Wiring. Wiring mean we manually configure it into the XML file. Auto Wiring mean we put the annotations in the Java file then Spring automatically scan the root-context where java configuration file, make it and put into the bag of Spring.

Spring bean只是由Spring容器管理的实例对象，也就是说，它们是由框架创建和连接的，并放入一个“对象袋”(容器)中，您以后可以从那里获取它们。

“连接”部分是依赖注入的全部内容，它的意思是你可以说“我将需要这个东西”，框架将遵循一些规则来为你获得适当的实例。

对于那些不习惯Spring的人来说，我认为Wikipedia Spring的文章有一个很好的描述:

Central to the Spring Framework is its inversion of control container, which provides a consistent means of configuring and managing Java objects using reflection. The container is responsible for managing object lifecycles of specific objects: creating these objects, calling their initialization methods, and configuring these objects by wiring them together. Objects created by the container are also called managed objects or beans. The container can be configured by loading XML files or detecting specific Java annotations on configuration classes. These data sources contain the bean definitions which provide the information required to create the beans. Objects can be obtained by means of either dependency lookup or dependency injection. Dependency lookup is a pattern where a caller asks the container object for an object with a specific name or of a specific type. Dependency injection is a pattern where the container passes objects by name to other objects, via either constructors, properties, or factory methods.