获取Spring容器上下文

1、web.xml必须配置ContextLoaderListener监听器以及Spring容器上下文配置文件：

    contextConfigLocation
    classpath:applicationContext.xml


    org.springframework.web.context.ContextLoaderListener

2、Spring容器上下文配置文件至少需要context命名空间及基础包扫描：

3、获取Spring容器上下文：

1)直接注入：

@Autowired
private ApplicationContext ac;

2）Spring容器上下文需要通过ServletContext获取，所以需要先获取到ServletContext：

public void getApplicationContext(HttpSession session) {
        ServletContext context = session.getServletContext();
        ApplicationContext ac = (ApplicationContext) context.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
        DemoController controller = ac.getBean("demoController", DemoController.class);
        System.out.println(controller);
    }

3）使用WebApplicationContextUtils获取：

public void getApplicationContext(HttpSession session) {
        ServletContext context = session.getServletContext();
        ApplicationContext ac = WebApplicationContextUtils.getWebApplicationContext(context);
        DemoController controller = ac.getBean("demoController", DemoController.class);
        System.out.println(controller);
    }

4）通过ApplicationContextAware接口获取：

1.编写类实现ApplicationContextAware接口并交给spring管理：

@Component
public class ApplicationContextProvider implements ApplicationContextAware {
    private ApplicationContext applicationContext;

    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    public ApplicationContext getApplicationContext() {
        return applicationContext;
    }
}

2.在需要上下文的类中注入这个类，获取spring容器上下文：

@Autowired
private ApplicationContextProvider applicationContextProvider;

@RequestMapping("/getApplicationContext")
public void getApplicationContext(HttpSession session) {
    ApplicationContext ac = applicationContextProvider.getApplicationContext();
    DemoController controller = ac.getBean("demoController", DemoController.class);
    System.out.println(controller);
}

5）Springboot项目获取Spring容器上下文：

@SpringBootApplication
public class SpringbootDemoApplication {

    private static ApplicationContext ac;

    public static void main(String[] args) {
       ac = SpringApplication.run(SpringbootDemoApplication.class, args);
    }

    @Bean
    public ApplicationContext getApplicationContext() {
        return ac;
    }

}

4：ClassPathXmlApplicationContext、WebApplicationContext、ApplicationContext关系：