SpringBoot常用配置簡介

SpringBoot常用配置簡介

1. SpringBoot中幾個常用的配置的簡單介紹

• 一個簡單的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簡介
  Spring.factories中的配置項， org.springframework.cloud.bootstrap.BootstrapConfiguration，會在Spring啟動之前的准備上下文階段將其加入到容器中。我們在介紹 @Configuration配置解析一文中曾詳細解釋Configuration中的解析。BootstrapConfiguration是在刷新（refresh）階段將class作為預選的配置類@Configuration注入到容器中的，在@Configuration配置解析階段會解析此class。

• 加載BootstrapConfiguration配置的類

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();

• 加載BootstrapConfiguration配置的類

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();//獲取需要加載的class源
		Assert.notEmpty(sources, "Sources must not be empty");
		load(context, sources.toArray(new Object[sources.size()]));//加載class
		listeners.contextLoaded(context);
      }

• ApplicationListener簡介
  org.springframework.context.ApplicationListener會在SpringBoot中幾個典型事件產生后調用onApplicationEvent方法。詳見Spring事件發布系統。

• Autoconfiguration簡介
  org.springframework.boot.autoconfigure.EnableAutoConfiguration是SpringBoot中最常見配置，用於自動配置。只要有@EnableAutoConfiguration注解，該配置的所有類都會自動加載到Spring容器中。