SpringBoot 获取上下文，获取bean的几种中方式 _SpringBoot

今日长缨在手，何时缚住苍龙。这篇文章主要讲述SpringBoot 获取上下文，获取bean的几种中方式相关的知识，希望能为你提供帮助。

传统Spring项目在写传统的spring项目中，一般通过初始化抽象类AbstractXmlApplicationContext 的实现类，并传入spring.xml，来获取应用上下文，最终通过getBean方法获取bean，如下：

ApplicationContext app1 = new FileSystemXmlApplicationContext("applicationContext.xml");
app1.getBean("beanName");
ApplicationContext app2 = new ClassPathXmlApplicationContext("applicationContext.xml");
app2.getBean("beanName");

SpringBoot项目获取bean的几种方式1. 通过启动类中返回的上下文获取

ConfigurableApplicationContext app = SpringApplication.run(BeanDemoApplication.class, args);
SpringUtil.setAppContext(app);

public class SpringUtil

private static ApplicationContext appContext;

public static void setAppContext(ApplicationContext appContext)
SpringUtil.appContext = appContext;

public static ApplicationContext getAppContext()
return appContext;

在第三方类中使用：

ApplicationContext appContext = SpringUtil.getAppContext();
appContext.getBean("beanName");

2. 通过工具类获取
??RequestContextUtils.findWebApplicationContext(HttpServletRequest request)??,??WebApplicationContextUtils.getWebApplicationContext(ServletContext sc)??
a. 在controller中传入request，例如：

public String test(HttpServletRequest request,HttpServletRequest response)
WebApplicationContext wc = RequestContextUtils.findWebApplicationContext(request);
wc.getBean("beanName");

WebApplicationContext wc2 = WebApplicationContextUtils.getWebApplicationContext(request.getServletContext());
wc2.getBean("beanName");

b. 在service中或者其他后端服务中获取：

HttpServletRequest request = ((ServletRequestAttributes)RequestContextHolder.getRequestAttributes()).getRequest();
WebApplicationContext wc = RequestContextUtils.findWebApplicationContext(request);
WebApplicationContext wc2 = WebApplicationContextUtils.getWebApplicationContext(request.getServletContext());

wc.getBean("beanName");
wc2.getBean("beanName");

3. 通过实现接口ApplicationContextAware

@Component
public class TestApplicationContextAware implements ApplicationContextAware

privateApplicationContext applicationContext;

@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
this.applicationContext = applicationContext;

public Object getBean(String beanName)
return applicationContext.getBean(beanName);

public ApplicationContext getApplicationContext()
return applicationContext;

在其他类中调用

@Autowired
private TestApplicationContextAware app;
public void testMethod()
app.getBean("beanName");

4. 通过继承抽象类：ApplicationObjectSupport，WebApplicationObjectSupport
原理参考第3点
5. 其他方式
在网上看，发现也可以直接调用：ContextLoader.getCurrentWebApplicationContext()，或者 ContextLoaderListener.getCurrentWebApplicationContext() 其实都是调用同一段代码，如下：

@Nullable
public static WebApplicationContext getCurrentWebApplicationContext()
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
if (ccl != null)
WebApplicationContext ccpt = currentContextPerThread.get(ccl);
if (ccpt != null)
return ccpt;

return currentContext;

说明：目前通过这种方式获取上下文为null，从代码可以看出，上下文是通过??currentContextPerThread.get(ccl)??? 来获取的，而currentContextPerThread缓存是通过方法??contextInitialized(ServletContextEvent event)?? 来初始化的，至于为何获取为空

【SpringBoot 获取上下文，获取bean的几种中方式】