[design-patterns] What design patterns are used in Spring framework?

What design patterns are used in Spring framework?

And of course dependency injection, or IoC (inversion of control), which is central to the whole BeanFactory/ApplicationContext stuff.

Spring is a collection of best-practise API patterns, you can write up a shopping list of them as long as your arm. The way that the API is designed encourages you (but doesn't force you) to follow these patterns, and half the time you follow them without knowing you are doing so.

Observer-Observable: it is used in ApplicationContext's event mechanism

Factory Method patter: BeanFactory for creating instance of an object Singleton : instance type can be singleton for a context Prototype : instance type can be prototype. Builder pattern: you can also define a method in a class who will be responsible for creating complex instance.

Spring container generates bean objects depending on the bean scope (singleton, prototype etc..). So this looks like implementing Abstract Factory pattern. In the Spring's internal implementation, I am sure each scope should be tied to specific factory kind class.

The DI thing actually is some kind of strategy pattern. Whenever you want to be some logic/implementation exchangeable you typically find an interface and an appropriate setter method on the host class to wire your custom implementation of that interface.

Factory pattern is also used for loading beans through BeanFactory and Application context.

Service Locator Pattern - ServiceLocatorFactoryBean keeps information of all the beans in the context. When client code asks for a service (bean) using name, it simply locates that bean in the context and returns it. Client code does not need to write spring related code to locate a bean.