Springboot中ConfigFileApplicationListener的作用是什么
今天就跟大家聊聊有关Springboot中ConfigFileApplicationListener的作用是什么,可能很多人都不太了解,为了让大家更加了解,小编给大家总结了以下内容,希望大家根据这篇文章可以有所收获。
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如下图1所示:
图1
ConfigFileApplicationListener实现了ApplicationListener,所以会收到Springboot的Event事件,如下List-1所示onApplicationEvent收到ApplicationEnvironmentPreparedEvent事件后,通过onApplicationEnvironmentPreparedEvent方法,获取spring.factories中的所有EnvironmentPostProcessor,并逐个调用EnvironmentPostProcessor的postProcessEnvironment方法。
List-1
@Override public void onApplicationEvent(ApplicationEvent event) { if (event instanceof ApplicationEnvironmentPreparedEvent) { onApplicationEnvironmentPreparedEvent( (ApplicationEnvironmentPreparedEvent) event); } if (event instanceof ApplicationPreparedEvent) { onApplicationPreparedEvent(event); } } private void onApplicationEnvironmentPreparedEvent( ApplicationEnvironmentPreparedEvent event) { ListpostProcessors = loadPostProcessors(); postProcessors.add(this); AnnotationAwareOrderComparator.sort(postProcessors); for (EnvironmentPostProcessor postProcessor : postProcessors) { postProcessor.postProcessEnvironment(event.getEnvironment(), event.getSpringApplication()); } } List loadPostProcessors() { return SpringFactoriesLoader.loadFactories(EnvironmentPostProcessor.class, getClass().getClassLoader()); }
List-1中onApplicationEnvironmentPreparedEvent方法里"postProcessors.add(this)",把当前实例也加入其中,所以来看看ConfigFileApplicationListener的postProcessEnvironment,如下List-2所示:
List-2
@Override public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) { addPropertySources(environment, application.getResourceLoader()); } ... protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) { RandomValuePropertySource.addToEnvironment(environment); new Loader(environment, resourceLoader).load(); }
List-2中的Loader是个内部类,在ConfigFileApplicationListener中,Loader的构造方法如下List-3所示,从spring.factories中获得PropertySourceLoader,实现类有俩个,即PropertiesPropertySourceLoader和YamlPropertySourceLoader。
List-3
... Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) { this.environment = environment; this.resourceLoader = (resourceLoader != null) ? resourceLoader : new DefaultResourceLoader(); this.propertySourceLoaders = SpringFactoriesLoader.loadFactories( PropertySourceLoader.class, getClass().getClassLoader()); } ...
List-4
# PropertySource Loaders org.springframework.boot.env.PropertySourceLoader=\ org.springframework.boot.env.PropertiesPropertySourceLoader,\ org.springframework.boot.env.YamlPropertySourceLoader
PropertiesPropertySourceLoader如下List-5,它支持的有properties和xml文件,并最终解析为Properties,封转到PropertiesPropertySource中。
List-5
public class PropertiesPropertySourceLoader implements PropertySourceLoader { public String[] getFileExtensions() { return new String[]{"properties", "xml"}; } public PropertySource> load(String name, Resource resource, String profile) throws IOException { if (profile == null) { Properties properties = PropertiesLoaderUtils.loadProperties(resource); if (!properties.isEmpty()) { return new PropertiesPropertySource(name, properties); } } return null; } }
YamlPropertySourceLoader如下List-6所示,支持的文件有yml和yaml,将yaml文件内容解析为map,之后封装到MapPropertySource。
List-6
public class YamlPropertySourceLoader implements PropertySourceLoader { public String[] getFileExtensions() { return new String[]{"yml", "yaml"}; } public PropertySource> load(String name, Resource resource, String profile) throws IOException { if (ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", (ClassLoader)null)) { YamlPropertySourceLoader.Processor processor = new YamlPropertySourceLoader.Processor(resource, profile); Mapsource = processor.process(); if (!source.isEmpty()) { return new MapPropertySource(name, source); } } return null; } ...
从ConfigFileApplicationListener中可以看到,Springboot通过事件触发解析配置文件的操作(如下List-7中的listeners.environmentPrepared(environment)处),其中properties和xml文件解析到JDK的Properties中,之后加入到Springboot的evironment中;yml和yaml文件解析到JDK的map中,之后加入到evironment中。
List-7
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,ApplicationArguments applicationArguments) { // Create and configure the environment ConfigurableEnvironment environment = getOrCreateEnvironment(); configureEnvironment(environment, applicationArguments.getSourceArgs()); listeners.environmentPrepared(environment); bindToSpringApplication(environment); if (!this.isCustomEnvironment) { environment = new EnvironmentConverter(getClassLoader()) .convertEnvironmentIfNecessary(environment, deduceEnvironmentClass()); } ConfigurationPropertySources.attach(environment); return environment; } ...
看完上述内容,你们对Springboot中ConfigFileApplicationListener的作用是什么有进一步的了解吗?如果还想了解更多知识或者相关内容,请关注创新互联行业资讯频道,感谢大家的支持。
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