Spring

The BeanFactory interface provides an advanced configuration mechanism capable of managing any type of object. ApplicationContext is a sub-interface of BeanFactory. It adds easier integration with Spring’s AOP features; message resource handling (for use in internationalization), event publication; and application-layer specific contexts such as the WebApplicationContext for use in web applications

 In short, the BeanFactory provides the configuration framework and basic functionality, and the ApplicationContext adds more enterprise-specific functionality. The ApplicationContext is a complete superset of the BeanFactory, and is used exclusively in this chapter in descriptions of Spring’s IoC container.

 

Setter injection should primarily only be used for optional dependencies that can be assigned reasonable default values within the class. Otherwise, not-null checks must be performed everywhere the code uses the dependency. One benefit of setter injection is that setter methods make objects of that class amenable to reconfiguration or re-injection later.

If you use predominantly constructor injection, it is possible to create an unresolvable circular dependency scenario.

One possible solution is to edit the source code of some classes to be configured by setters rather than constructors. Alternatively, avoid constructor injection and use setter injection only. In other words, although it is not recommended, you can configure circular dependencies with setter injection.

using the idref tag allows the container to validate at deployment time that the referenced, named bean actually exists. In the second variation, no validation is performed on the value that is passed to the targetName property of the client bean.

It is recommended that you do not use the InitializingBean interface because it unnecessarily couples the code to Spring. Alternatively, use the @PostConstruct annotation or specify a POJO initialization method.

Multiple lifecycle mechanisms configured for the same bean, with different initialization methods, are called as follows:

• Methods annotated with @PostConstruct
• afterPropertiesSet() as defined by the InitializingBean callback interface
• A custom configured init() method

Destroy methods are called in the same order:

• Methods annotated with @PreDestroy
• destroy() as defined by the DisposableBean callback interface
• A custom configured destroy() method