Application Context定义

简单来说就是Spring中的高级容器，可以获取容器中的各种bean组件，注册监听事件，加载资源文件等功能。

具体定义可以参考官网：https://spring.io/understanding/application-context

Understanding Application Context

The ApplicationContext is the central interface within a Spring application for providing configuration information to the application. It is read-only at run time, but can be reloaded if necessary and supported by the application. A number of classes implement the ApplicationContext interface, allowing for a variety of configuration options and types of applications.

The ApplicationContext provides:

• Bean factory methods for accessing application components.

• The ability to load file resources in a generic fashion.

• The ability to publish events to registered listeners.

• The ability to resolve messages to support internationalization.

• Inheritance from a parent context.

Application Context获取的几种方式

1、直接注入

@Resource

private ApplicationContext ctx;

2、实现ApplicationContextAware接口（推荐）

WebApplicationObjectSupport extends ApplicationObjectSupport implements ServletContextAware

从上面的继承关系看，获取Application Context还可以继承WebApplicationObjectSupport 、ApplicationObjectSupport，继承加强耦合性不推荐。

3、WebApplicationContextUtils工具类

ApplicationContext ctx = WebApplicationContextUtils.getWebApplicationContext(request.getSession().getServletContext());

4、从当前线程绑定获取（Spring boot不支持）

ApplicationContext ctx = ContextLoader.getCurrentWebApplicationContext();