
public ConfigurableApplicationContext run(String... args) {// 略 1~3 ...try {// 4、ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);ConfigurableEnvironment environment = prepareEnvironment(listeners,applicationArguments);// 略 5~13 ...return context;}catch (Throwable ex) {// 略 14 ...}
}

1、创建DefaultApplicationArguments实例

DefaultApplicationArguments 是啥？说白了，它就是用来封装运行参数并提供一些方便访问参数的方法。

public DefaultApplicationArguments(String[] args) {Assert.notNull(args, "Args must not be null");this.source = new Source(args);this.args = args;
}

创建 DefaultApplicationArguments 实例时，初始化两个实例变量，最终的结果如下图所示（运行参数设置了 --server.port=8001），大家可以自行查看源码，简单不赘述

2、prepareEnvironment

这个方法做了三件事情：
1、获取或者创建ConﬁgurableEnvironment - StandardServletEnviroment
web环境会创建StandardServletEnviroment，
2、
3、

2.1 获取或者创建ConﬁgurableEnvironment


/****** o.s.boot.SpringApplication ******/private ConfigurableEnvironment getOrCreateEnvironment() {if (this.environment != null) {return this.environment;}if (this.webEnvironment) {return new StandardServletEnvironment();}return new StandardEnvironment();
}

ConfigurableEnvironment 是个接口，主要作用是提供当前运行环境的公开接口，其中 StandardServletEnviroment 和 StandardEnvironment 都是其实现类，类图如下：

StandardServletEnviroment 类图

我们在创建 StandardServletEnviroment 实例拥有从父类 AbstractEnviroment 继承来的 MutablePropertySources 类型属性 propertySources ，在创建实例时，调用 customizePropertySources(...) 方法向propertySources放入一些PropertySource对象。

调用关系

源码参考：

/****** o.s.core.env.AbstractEnvironment ******/
public AbstractEnvironment() {customizePropertySources(this.propertySources);if (logger.isDebugEnabled()) {logger.debug("Initialized " + getClass().getSimpleName() + " with PropertySources " + this.propertySources);}
}/****** o.s.web.context.support.StandardEnvironment ******/
protected void customizePropertySources(MutablePropertySources propertySources) {propertySources.addLast(new MapPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));propertySources.addLast(new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment()));
}/****** o.s.web.context.support.StandardServletEnvironment ******/
protected void customizePropertySources(MutablePropertySources propertySources) {propertySources.addLast(new StubPropertySource(SERVLET_CONFIG_PROPERTY_SOURCE_NAME));propertySources.addLast(new StubPropertySource(SERVLET_CONTEXT_PROPERTY_SOURCE_NAME));if (JndiLocatorDelegate.isDefaultJndiEnvironmentAvailable()) {propertySources.addLast(new JndiPropertySource(JNDI_PROPERTY_SOURCE_NAME));}super.customizePropertySources(propertySources);
}

执行完这些代码后的内存状态如下图：

StandardServletEnvironment 内存状态图

点击查看：System.getProperties()内容
点击查看：System.getenv()内容

2.2 配置ConﬁgurableEnvironment

 protected void configureEnvironment(ConfigurableEnvironment environment,String[] args) {configurePropertySources(environment, args);configureProfiles(environment, args);}

2.2.1 配置PropertySources

所谓的配置PropertySource ，其实就是向环境中添加 PropertSource ，画个图看一下

StandardServletEnvironment 内存状态图

 private boolean addCommandLineProperties = true;// 在environment中添加、删除或重新排序所有的propertysource。protected void configurePropertySources(ConfigurableEnvironment environment,String[] args) {MutablePropertySources sources = environment.getPropertySources();// 我的 defaultProperties 为null，什么时候有值？ 硬编码设置默认属性时有值！参考：[1、硬编码]if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) {// 放在List的最后位置，表示优先级最低sources.addLast(new MapPropertySource("defaultProperties", this.defaultProperties));}if (this.addCommandLineProperties && args.length > 0) {// COMMAND_LINE_PROPERTY_SOURCE_NAME 值为 "commandLineArgs"String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;// 从 MutablePropertySources 的变量 List<PropertySource<?>> propertySourceList  中// 查找有没有名称为 commandLineArgs 的 PropertySource，我们看一下上面的“内存状态图”，里面是没有的if (sources.contains(name)) {PropertySource<?> source = sources.get(name);CompositePropertySource composite = new CompositePropertySource(name);composite.addPropertySource(new SimpleCommandLinePropertySource(name + "-" + args.hashCode(), args));composite.addPropertySource(source);sources.replace(name, composite);}else {// 将 命令行参数封装为SimpleCommandLinePropertySource 放入MutablePropertySources 中// 放在第一个表示优先级最高sources.addFirst(new SimpleCommandLinePropertySource(args));}}}

参考链接： [1、硬编码]

我们来看看StandardServletEnvironment 中 MutablePropertySources 的 List<PropertySource<?>> propertySourceList 变量的结果：

/****************** StandardServletEnvironment ******************/
environment = {StandardServletEnvironment@1914} "..."ACTIVE_PROFILES_PROPERTY_NAME = "spring.profiles.active"activeProfiles = {LinkedHashSet@1998}  size = 0DEFAULT_PROFILES_PROPERTY_NAME = "spring.profiles.default"defaultProfiles = {LinkedHashSet@2000}  size = 1IGNORE_GETENV_PROPERTY_NAME = "spring.getenv.ignore"JNDI_PROPERTY_SOURCE_NAME = "jndiProperties"logger = {SLF4JLocationAwareLog@1978} propertyResolver = {PropertySourcesPropertyResolver@2003} /****************** MutablePropertySources  ******************/propertySources = {MutablePropertySources@1931} "[...]"logger = {SLF4JLocationAwareLog@1978} /****************** MutablePropertySources#List<PropertySource>propertySourceList ******************/propertySourceList = {CopyOnWriteArrayList@1979}  size = 50 = {SimpleCommandLinePropertySource@..} "SimpleCommandLinePropertySource {name='commandLineArgs'}"1 = {PropertySource$StubPropertySource@..} "StubPropertySource {name='servletConfigInitParams'}"2 = {PropertySource$StubPropertySource@..} "StubPropertySource {name='servletContextInitParams'}"3 = {MapPropertySource@1984} "MapPropertySource {name='systemProperties'}"4 = {SystemEnvironmentPropertySource@..} "SystemEnvironmentPropertySource {name='systemEnvironment'}"RESERVED_DEFAULT_PROFILE_NAME = "default"SERVLET_CONFIG_PROPERTY_SOURCE_NAME = "servletConfigInitParams"SERVLET_CONTEXT_PROPERTY_SOURCE_NAME = "servletContextInitParams"SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = "systemEnvironment"SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = "systemProperties"

2.2.2 配置 profiles

设置应用程序的 profiles，profiles 的作用就是将不同的配置参数作用于不同的的环境。

protected void configureProfiles(ConfigurableEnvironment environment, String[] args) {environment.getActiveProfiles(); // 确保已经初始化 ensure they are initialized// But these ones should go first (last wins in a property key clash)Set<String> profiles = new LinkedHashSet<String>(this.additionalProfiles);profiles.addAll(Arrays.asList(environment.getActiveProfiles()));environment.setActiveProfiles(profiles.toArray(new String[profiles.size()]));
}

2.2.3

onApplicationEvent:167, ConfigFileApplicationListener (o.s.boot.context.config)
doInvokeListener:172, SimpleApplicationEventMulticaster (o.s.context.event)
invokeListener:165, SimpleApplicationEventMulticaster (o.s.context.event)
multicastEvent:139, SimpleApplicationEventMulticaster (o.s.context.event)
multicastEvent:122, SimpleApplicationEventMulticaster (o.s.context.event)
environmentPrepared:74, EventPublishingRunListener (o.s.boot.context.event)
environmentPrepared:54, SpringApplicationRunListeners (o.s.boot)
prepareEnvironment:325, SpringApplication (o.s.boot)
run:296, SpringApplication (o.s.boot)
main:20, PropertyTestMainSpringApplication (com.yh.stu.springboot.property)

@Overridepublic void multicastEvent(final ApplicationEvent event, ResolvableType eventType) {ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) {Executor executor = getTaskExecutor();if (executor != null) {executor.execute(new Runnable() {@Overridepublic void run() {invokeListener(listener, event);}});}else {invokeListener(listener, event);}}}// getApplicationListeners(event, type)的结果:
result = {LinkedList@1976}  size = 70 = {ConfigFileApplicationListener@1864} 1 = {AnsiOutputApplicationListener@1978} 2 = {LoggingApplicationListener@1979} 3 = {ClasspathLoggingApplicationListener@1980} 4 = {BackgroundPreinitializer@1981} 5 = {DelegatingApplicationListener@1982} 6 = {FileEncodingApplicationListener@1983}

Q&A :

1、❓ // TODO 查看其它 Listener 是如何判断是否监听特定event的

ConfigFileApplicationListener也监听了 ApplicationEnvironmentPreparedEvent 事件，是因为实现了 SmartApplicationListener 接口的方法supportsEventType，这里会判断是否支持特定的 event
从所有Listener中获取监听特定event 的ListenersupportsEventType

supportsEventType:156, ConfigFileApplicationListener (o.s.boot.context.config)
supportsEventType:64, GenericApplicationListenerAdapter (o.s.context.event)
supportsEvent:289, AbstractApplicationEventMulticaster (o.s.context.event)
retrieveApplicationListeners:221, AbstractApplicationEventMulticaster (o.s.context.event)
getApplicationListeners:192, AbstractApplicationEventMulticaster (o.s.context.event)
multicastEvent:128, SimpleApplicationEventMulticaster (o.s.context.event)
multicastEvent:122, SimpleApplicationEventMulticaster (o.s.context.event)
environmentPrepared:74, EventPublishingRunListener (o.s.boot.context.event)
environmentPrepared:54, SpringApplicationRunListeners (o.s.boot)
prepareEnvironment:325, SpringApplication (o.s.boot)
run:296, SpringApplication (o.s.boot)
run:1118, SpringApplication (o.s.boot)
run:1107, SpringApplication (o.s.boot)
main:20, SpringBootSourceStuApplication (com.yh.stu.springboot.hello)

2、如何解析application.yml/properties 文件的时机？

搜索：application.properties，找到 ConfigFileApplicationListener ，搜索yml 找到load方法，打上断点

调用栈：

getAllFileExtensions:205, PropertySourcesLoader (o.s.boot.env)
load:447, ConfigFileApplicationListener$Loader (o.s.boot.context.config)
load:386, ConfigFileApplicationListener$Loader (o.s.boot.context.config)
addPropertySources:225, ConfigFileApplicationListener (o.s.boot.context.config)
postProcessEnvironment:195, ConfigFileApplicationListener (o.s.boot.context.config)
onApplicationEnvironmentPreparedEvent:182, ConfigFileApplicationListener (o.s.boot.context.config)
onApplicationEvent:168, ConfigFileApplicationListener (o.s.boot.context.config)
doInvokeListener:172, SimpleApplicationEventMulticaster (o.s.context.event)
invokeListener:165, SimpleApplicationEventMulticaster (o.s.context.event)
multicastEvent:139, SimpleApplicationEventMulticaster (o.s.context.event)
multicastEvent:122, SimpleApplicationEventMulticaster (o.s.context.event)
environmentPrepared:74, EventPublishingRunListener (o.s.boot.context.event)
environmentPrepared:54, SpringApplicationRunListeners (o.s.boot)
prepareEnvironment:325, SpringApplication (o.s.boot)
run:296, SpringApplication (o.s.boot)
run:1118, SpringApplication (o.s.boot)
run:1107, SpringApplication (o.s.boot)
main:20, SpringBootSourceStuApplication (com.yh.stu.springboot.hello)

public PropertySourcesLoader(MutablePropertySources propertySources) {Assert.notNull(propertySources, "PropertySources must not be null");this.propertySources = propertySources;// 两个：YamlPropertySourceLoader PropertiesPropertySourceLoader this.loaders = SpringFactoriesLoader.loadFactories(PropertySourceLoader.class,getClass().getClassLoader());
}

附-YamlPropertySourceLoader

public class YamlPropertySourceLoader implements PropertySourceLoader {@Overridepublic String[] getFileExtensions() {return new String[] { "yml", "yaml" };}@Overridepublic PropertySource<?> load(String name, Resource resource, String profile)throws IOException {if (ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", null)) {Processor processor = new Processor(resource, profile);Map<String, Object> source = processor.process();if (!source.isEmpty()) {return new MapPropertySource(name, source);}}return null;}/*** {@link YamlProcessor} to create a {@link Map} containing the property values.* Similar to {@link YamlPropertiesFactoryBean} but retains the order of entries.*/private static class Processor extends YamlProcessor {Processor(Resource resource, String profile) {if (profile == null) {setMatchDefault(true);setDocumentMatchers(new SpringProfileDocumentMatcher());}else {setMatchDefault(false);setDocumentMatchers(new SpringProfileDocumentMatcher(profile));}setResources(resource);}@Overrideprotected Yaml createYaml() {return new Yaml(new StrictMapAppenderConstructor(), new Representer(),new DumperOptions(), new Resolver() {@Overridepublic void addImplicitResolver(Tag tag, Pattern regexp,String first) {if (tag == Tag.TIMESTAMP) {return;}super.addImplicitResolver(tag, regexp, first);}});}public Map<String, Object> process() {final Map<String, Object> result = new LinkedHashMap<String, Object>();process(new MatchCallback() {@Overridepublic void process(Properties properties, Map<String, Object> map) {result.putAll(getFlattenedMap(map));}});return result;}}}

附-PropertiesPropertySourceLoader

public class PropertiesPropertySourceLoader implements PropertySourceLoader {@Overridepublic String[] getFileExtensions() {return new String[] { "properties", "xml" };}@Overridepublic 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;}}

2.4、准备Spring Boot的环境 prepareEnvironment相关推荐

spring boot分环境导出自定义xml配置
背景介绍: 由于新的spring boot项目需要使用老的jar包,老的jar包的配置是用xml方式配置的,而且开发development.测试test.集成off.正式production环境都会有 ...
spring boot多环境配置
spring boot多环境配置通过多环境配置,可以实现生产环境和测试环境灵活切换. 主配置文件加载生产环境配置文件语法: spring.profiles.active=pro 注意一旦pro被激活 ...
Spring Boot——不同环境调用不同的配置文件解决方案
问题描述我们在开发Spring Boot应用时,通常同一套程序会被应用和安装到几个不同的环境,比如:开发.测试.生产等.其中每个环境的数据库地址.服务器端口等等配置都会不同,如果在为不同环境打包时都 ...
从零搭建一个 Spring Boot 开发环境！Spring Boot+Mybatis+Swagger2 环境搭建
从零搭建一个 Spring Boot 开发环境!Spring Boot+Mybatis+Swagger2 环境搭建本文简介为什么使用Spring Boot 搭建怎样一个环境开发环境导入快速启动 ...
学习第五篇：【SpringBoot-Labs】Spring Boot 调试环境、热部署入门、Lombok、MapStruct入门
本周(8.21-8.27)将学习芋道 Spring Boot的以下文章: 8.21: 快速入门 8.22:Spring Boot 自动配置原理 .Jar 启动原理 8.23:调试环境. 热部署入门.消 ...
普歌-云言团队-Spring Boot入门:环境搭建Spring Boot HelloWorld
Spring Boot入门:环境搭建Spring Boot HelloWorld 前言:SpringBoot 是来简化Spring应用开发, 约定大于配置, 去繁从简, just run就能创建一个独 ...
嗯，挺全乎儿的，Spring Boot 多环境配置都在这儿了，你喜欢哪一种呢？
目录前言 Spring Boot 自带的多环境配置创建不同环境的配置文件指定运行的环境 Maven 的多环境配置创建多环境配置文件定义激活的变量 pom 文件中定义 profiles 资源过 ...
Linux系统CentOS 7配置Spring Boot运行环境
从阿里云新买的一台Linux服务器,用来部署SpringBoot应用,由于之前一直使用Debian版本,环境配置有所不同,也较为繁琐,本文主要介绍CentOS下配置SpringBoot环境的过程新建 ...
Spring Boot基础学习笔记05：Spring Boot多环境配置
文章目录零.学习目标 1.掌握使用Profile文件进行多环境配置 2.掌握使用@Profile注解进行多环境配置 3.熟悉随机值设置以及参数间引用一.项目进行多环境配置的必要性二.使用Prof ...

2.4、准备Spring Boot的环境 prepareEnvironment