如何在应用代码里获取到 Management Spring Context

如果应用代码想获取到Management Spring Context，可以通过这个bean：org.springframework.boot.actuate.autoconfigure.ManagementContextResolver

spring boot在创建Management Spring Context时，就会保存到ManagementContextResolver里。

@Configuration
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class })
@ConditionalOnWebApplication
@AutoConfigureAfter({ PropertyPlaceholderAutoConfiguration.class,
        EmbeddedServletContainerAutoConfiguration.class, WebMvcAutoConfiguration.class,
        ManagementServerPropertiesAutoConfiguration.class,
        RepositoryRestMvcAutoConfiguration.class, HypermediaAutoConfiguration.class,
        HttpMessageConvertersAutoConfiguration.class })
public class EndpointWebMvcAutoConfiguration
        implements ApplicationContextAware, BeanFactoryAware, SmartInitializingSingleton {
      @Bean
        public ManagementContextResolver managementContextResolver() {
            return new ManagementContextResolver(this.applicationContext);
        }

        @Bean
        public ManagementServletContext managementServletContext(
                final ManagementServerProperties properties) {
            return new ManagementServletContext() {

                @Override
                public String getContextPath() {
                    return properties.getContextPath();
                }

            };
        }

如何在Endpoints代码里获取应用的Spring context

spring boot本身没有提供方法，应用可以自己写一个@Configuration，保存应用的Spring context，然后在endpoints代码里再取出来。

ApplicationContext.setParent(ApplicationContext) 到底发生了什么

从spring的代码就可以看出来，主要是把parent的environment里的propertySources加到child里。这也就是spring cloud config可以生效的原因。

// org.springframework.context.support.AbstractApplicationContext.setParent(ApplicationContext)
/**
 * Set the parent of this application context.
 * <p>The parent {@linkplain ApplicationContext#getEnvironment() environment} is
 * {@linkplain ConfigurableEnvironment#merge(ConfigurableEnvironment) merged} with
 * this (child) application context environment if the parent is non-{@code null} and
 * its environment is an instance of {@link ConfigurableEnvironment}.
 * @see ConfigurableEnvironment#merge(ConfigurableEnvironment)
 */
@Override
public void setParent(ApplicationContext parent) {
  this.parent = parent;
  if (parent != null) {
    Environment parentEnvironment = parent.getEnvironment();
    if (parentEnvironment instanceof ConfigurableEnvironment) {
      getEnvironment().merge((ConfigurableEnvironment) parentEnvironment);
    }
  }
}