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。