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启动类

@SpringBootApplication
public class TestApplication {

    public static void main(String[] args) {
        SpringApplication.run(TestApplication.class, args);
    }
}

点进run方法

	public static ConfigurableApplicationContext run(Class<?> primarySource, String... args) {
		return run(new Class<?>[] { primarySource }, args);
	}

继续点击run方法

	public static ConfigurableApplicationContext run(Class<?>[] primarySources, String[] args) {
		return new SpringApplication(primarySources).run(args);
	}

点进去SpringApplication方法

	public SpringApplication(Class<?>... primarySources) {
		this(null, primarySources);
	}

点进去this

	public SpringApplication(ResourceLoader resourceLoader, Class<?>... primarySources) {
		this.resourceLoader = resourceLoader;
		Assert.notNull(primarySources, "PrimarySources must not be null");
		this.primarySources = new LinkedHashSet<>(Arrays.asList(primarySources));
		this.webApplicationType = WebApplicationType.deduceFromClasspath();
		this.bootstrapRegistryInitializers = new ArrayList<>(
				getSpringFactoriesInstances(BootstrapRegistryInitializer.class));
		setInitializers((Collection) getSpringFactoriesInstances(ApplicationContextInitializer.class));
		setListeners((Collection) getSpringFactoriesInstances(ApplicationListener.class));
		this.mainApplicationClass = deduceMainApplicationClass();
	}

新建一个spring实例,主要就是用来加载资源的
点进入getSpringFactoriesInstances方法

	private <T> Collection<T> getSpringFactoriesInstances(Class<T> type) {
		return getSpringFactoriesInstances(type, new Class<?>[] {});
	}

继续进入getSpringFactoriesInstances方法

	private <T> Collection<T> getSpringFactoriesInstances(Class<T> type, Class<?>[] parameterTypes, Object... args) {
		ClassLoader classLoader = getClassLoader();
		// Use names and ensure unique to protect against duplicates
		Set<String> names = new LinkedHashSet<>(SpringFactoriesLoader.loadFactoryNames(type, classLoader));
		List<T> instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
		AnnotationAwareOrderComparator.sort(instances);
		return instances;
	}

loadFactoryNames方法

	public static List<String> loadFactoryNames(Class<?> factoryType, @Nullable ClassLoader classLoader) {
		ClassLoader classLoaderToUse = classLoader;
		if (classLoaderToUse == null) {
			classLoaderToUse = SpringFactoriesLoader.class.getClassLoader();
		}
		String factoryTypeName = factoryType.getName();
		return loadSpringFactories(classLoaderToUse).getOrDefault(factoryTypeName, Collections.emptyList());
	}

进入loadSpringFactories方法

	private static Map<String, List<String>> loadSpringFactories(ClassLoader classLoader) {
		Map<String, List<String>> result = cache.get(classLoader);
		if (result != null) {
			return result;
		}

		result = new HashMap<>();
		try {
        //FACTORIES_RESOURCE_LOCATIN是 META-INF/spring.factories
			Enumeration<URL> urls = classLoader.getResources(FACTORIES_RESOURCE_LOCATION);
			while (urls.hasMoreElements()) {
				URL url = urls.nextElement();
				UrlResource resource = new UrlResource(url);
				Properties properties = PropertiesLoaderUtils.loadProperties(resource);
				for (Map.Entry<?, ?> entry : properties.entrySet()) {
					String factoryTypeName = ((String) entry.getKey()).trim();
					String[] factoryImplementationNames =
							StringUtils.commaDelimitedListToStringArray((String) entry.getValue());
					for (String factoryImplementationName : factoryImplementationNames) {
						result.computeIfAbsent(factoryTypeName, key -> new ArrayList<>())
								.add(factoryImplementationName.trim());
					}
				}
			}

			// Replace all lists with unmodifiable lists containing unique elements
			result.replaceAll((factoryType, implementations) -> implementations.stream().distinct()
					.collect(Collectors.collectingAndThen(Collectors.toList(), Collections::unmodifiableList)));
			cache.put(classLoader, result);
		}
		catch (IOException ex) {
			throw new IllegalArgumentException("Unable to load factories from location [" +
					FACTORIES_RESOURCE_LOCATION + "]", ex);
		}
		return result;
	}

配置文件

默认

  • application.properties 或者application.yml

    如果这两个都存在的情况下,同样的配置,后面的配置回覆盖前面的
    如果一个项目有多个modual,一个启动类,其他modual都添加到了启动类modual的pom文件中,那么配置文件也是对应的,后面会覆盖前面的配置文件

profile

  • 这个就是我们要区分环境的时候需要搞的配置文件了,因为在实际项目开发的时候,是不可能一个环境的,一般都是多个环境,比如开发环境 测试环境 预生产环境 生产环境
  • 文件名是 application-{profile}.properties/yml
  • 但是如果仅仅新建了这样的一个配置文件是不会生效的,我们需要去激活这类的profile的配置文件

激活方式

  1. 在配置文件中指定 spring.profiles.active=dev
  2. 命令行:
    • java -jar spring-boot-02-config-0.0.1-SNAPSHOT.jar --spring.profiles.active=dev;
  3. 虚拟机参数; -Dspring.profiles.active=dev

加载位置

springboot 启动会扫描以下位置的application.properties或者application.yml文件作为Spring boot的默认配置文件

  • file:./config/
  • file:./
  • classpath:/config/
  • classpath:/
    • 优先级由高到底,高优先级的配置会覆盖低优先级的配置
    • SpringBoot会从这四个位置全部加载主配置文件;互补配置;
    • 我们还可以通过spring.config.location来改变默认的配置文件位置项目打包好以后,我们可以使用命令行参数的形式,启动项目的时候来指定配置文件的新位置;指定配置文件和默认加载的这些配置文件共同起作用形成互补配置;
java -jar spring-boot-02-config-02-0.0.1-SNAPSHOT.jar --spring.config.location=G:/application.properties

参考

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