SpringBoot常用配置简介

SpringBoot常用配置简介

1. SpringBoot中几个常用的配置的简单介绍

• 一个简单的Spring.factories

   # Bootstrap components
   org.springframework.cloud.bootstrap.BootstrapConfiguration=\
   org.springframework.cloud.config.server.bootstrap.ConfigServerBootstrapConfiguration
  
   # Application listeners
   org.springframework.context.ApplicationListener=\
   org.springframework.cloud.config.server.bootstrap.ConfigServerBootstrapApplicationListener
   # Autoconfiguration
   org.springframework.boot.autoconfigure.EnableAutoConfiguration=\
   org.springframework.cloud.config.server.config.EncryptionAutoConfiguration,\
   org.springframework.cloud.config.server.config.SingleEncryptorAutoConfiguration
  

• BootstrapConfiguration简介
  
  Spring.factories中的配置项， org.springframework.cloud.bootstrap.BootstrapConfiguration，会在Spring启动之前的准备上下文阶段将其加入到容器中。我们在介绍 @Configuration配置解析一文中曾详细解释Configuration中的解析。BootstrapConfiguration是在刷新（refresh）阶段将class作为预选的配置类@Configuration注入到容器中的，在@Configuration配置解析阶段会解析此class。

• 加载BootstrapConfiguration配置的类

List<String> names = SpringFactoriesLoader
				.loadFactoryNames(BootstrapConfiguration.class, classLoader);
		for (String name : StringUtils.commaDelimitedListToStringArray(
				environment.getProperty("spring.cloud.bootstrap.sources", ""))) {
			names.add(name);
		}
		// TODO: is it possible or sensible to share a ResourceLoader?
		SpringApplicationBuilder builder = new SpringApplicationBuilder()
				.profiles(environment.getActiveProfiles()).bannerMode(Mode.OFF)
				.environment(bootstrapEnvironment)
				.properties("spring.application.name:" + configName)
				.registerShutdownHook(false).logStartupInfo(false).web(false);
		List<Class<?>> sources = new ArrayList<>();
		for (String name : names) {
			Class<?> cls = ClassUtils.resolveClassName(name, null);
			try {
				cls.getDeclaredAnnotations();
			}
			catch (Exception e) {
				continue;
			}
			sources.add(cls);
		}
		builder.sources(sources.toArray(new Class[sources.size()]));
		AnnotationAwareOrderComparator.sort(sources);
		final ConfigurableApplicationContext context = builder.run();

• 加载BootstrapConfiguration配置的类

private void prepareContext(ConfigurableApplicationContext context,ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,ApplicationArguments applicationArguments, Banner printedBanner) {
		context.setEnvironment(environment);
		postProcessApplicationContext(context);
		applyInitializers(context);
		listeners.contextPrepared(context);
		if (this.logStartupInfo) {
			logStartupInfo(context.getParent() == null);
			logStartupProfileInfo(context);
		}
    // Add boot specific singleton beans
		context.getBeanFactory().registerSingleton("springApplicationArguments",
				applicationArguments);
		if (printedBanner != null) {
			context.getBeanFactory().registerSingleton("springBootBanner", printedBanner);
		}

		// Load the sources
		Set<Object> sources = getSources();//获取需要加载的class源
		Assert.notEmpty(sources, "Sources must not be empty");
		load(context, sources.toArray(new Object[sources.size()]));//加载class
		listeners.contextLoaded(context);
      }

• ApplicationListener简介
  
  org.springframework.context.ApplicationListener会在SpringBoot中几个典型事件产生后调用onApplicationEvent方法。详见Spring事件发布系统。

• Autoconfiguration简介
  
  org.springframework.boot.autoconfigure.EnableAutoConfiguration是SpringBoot中最常见配置，用于自动配置。只要有@EnableAutoConfiguration注解，该配置的所有类都会自动加载到Spring容器中。