獲取Spring的ApplicationContext的幾種方式

Application Context定義

簡單來講就是Spring中的高級容器，能夠獲取容器中的各類bean組件，註冊監聽事件，加載資源文件等功能。

具體定義能夠參考官網：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獲取的幾種方式

一、直接注入

@Resource

private ApplicationContext ctx;

二、實現ApplicationContextAware接口（推薦）

WebApplicationObjectSupport extends ApplicationObjectSupport implements ServletContextAware

從上面的繼承關係看，獲取Application Context還能夠繼承WebApplicationObjectSupport 、ApplicationObjectSupport，繼承增強耦合性不推薦。

三、WebApplicationContextUtils工具類

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

四、從當前線程綁定獲取（Spring boot不支持）

ApplicationContext ctx = ContextLoader.getCurrentWebApplicationContext();

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