Part.1
流程分析
入口程序
在 SpringApplication#run(String... args) 方法中，外部化配置关键流程分为以下四步
public ConfigurableApplicationContext
run(String... args) {
...
SpringApplicationRunListeners listeners = getRunListeners(args); // 1
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments); // 2
configureIgnoreBeanInfo(environment);
Banner printedBanner = printBanner(environment);
context = createApplicationContext();
exceptionReporters = getSpringFactoriesInstances(
SpringBootExceptionReporter.class,
new Class[] { ConfigurableApplicationContext.class }, context);
prepareContext(context, environment, listeners, applicationArguments,
printedBanner); // 3
refreshContext(context); // 4
afterRefresh(context, applicationArguments);
stopWatch.stop();
if (this.logStartupInfo) {
new StartupInfoLogger(this.mainApplicationClass)
.logStarted(getApplicationLog(), stopWatch);
}
listeners.started(context);
callRunners(context, applicationArguments);
}
...
}
关键流程思维导图
关键流程详解
对入口程序中标记的四步，分析如下
1
SpringApplication#getRunListeners
加载 META-INF/spring.factories
获取 SpringApplicationRunListener
的实例集合，存放的对象是 EventPublishingRunListener 类型 以及自定义的 SpringApplicationRunListener 实现类型
2
SpringApplication#prepareEnvironment
prepareEnvironment 方法中，主要的三步如下
private ConfigurableEnvironment
prepareEnvironment(SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments) {
// Create and configure the environment
ConfigurableEnvironment environment = getOrCreateEnvironment(); // 2.1
configureEnvironment(environment, applicationArguments.getSourceArgs()); // 2.2
listeners.environmentPrepared(environment); // 2.3
...
return environment;
}
2.1、getOrCreateEnvironment 方法
在 WebApplicationType.SERVLET web应用类型下，会创建 StandardServletEnvironment，本文以 StandardServletEnvironment 为例，类的层次结构如下
当创建 StandardServletEnvironment，StandardServletEnvironment 父类 AbstractEnvironment 调用 customizePropertySources 方法，会执行 StandardServletEnvironment#customizePropertySources和 StandardEnvironment#customizePropertySources ，源码如下AbstractEnvironment
public AbstractEnvironment() {
customizePropertySources(this.propertySources);
if (logger.isDebugEnabled()) {
logger.debug("Initialized " + getClass().getSimpleName() + " with PropertySources " + this.propertySources);
}
}
StandardServletEnvironment#customizePropertySources
/** Servlet context init parameters property source name: {@value} */
public static final
StringSERVLET_CONTEXT_PROPERTY_SOURCE_NAME = "servletContextInitParams";
/** Servlet config init parameters property source name: {@value} */
public static final String
SERVLET_CONFIG_PROPERTY_SOURCE_NAME = "servletConfigInitParams";
/** JNDI property source name: {@value} */
public static final String
JNDI_PROPERTY_SOURCE_NAME = "jndiProperties";
@Override
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);
}
StandardEnvironment#customizePropertySources
/** System environment property source name: {@value} */
public static final String
SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME = "systemEnvironment";
/** JVM system properties property source name: {@value} */
public static final String
SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME = "systemProperties";
@Override
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());
}
PropertySources 顺序：
1. servletConfigInitParams
2. servletContextInitParams
3. jndiProperties
4. systemProperties
5. systemEnvironment
PropertySources 与 PropertySource 关系为 1 对 N
2.2、configureEnvironment 方法
调用 configurePropertySources(environment, args)， 在方法里面设置 Environment 的 PropertySources ， 包含 defaultProperties 和
SimpleCommandLinePropertySource（commandLineArgs），PropertySources 添加 defaultProperties 到最后，添加
SimpleCommandLinePropertySource（commandLineArgs）到最前面
PropertySources 顺序：
1. commandLineArgs
2. servletConfigInitParams
3. servletContextInitParams
4. jndiProperties
5. systemProperties
6. systemEnvironment
7. defaultProperties
2.3、listeners.environmentPrepared 方法
会按优先级顺序遍历执行 SpringApplicationRunListener#environmentPrepared，比如 EventPublishingRunListener 和 自定义的 SpringApplicationRunListener
EventPublishingRunListener 发布
ApplicationEnvironmentPreparedEvent 事件
ConfigFileApplicationListener 监听
ApplicationEvent 事件 、处理 ApplicationEnvironmentPreparedEvent 事件，加载所有 EnvironmentPostProcessor 包括自己，然后按照顺序进行方法回调
---ConfigFileApplicationListener#postProcessEnvironment方法回调 ，然后addPropertySources 方法调用
RandomValuePropertySource#addToEnvironment，在 systemEnvironment 后面添加 random，然后添加配置文件的属性源（详见
源码ConfigFileApplicationListener.Loader#load()
扩展点
自定义 SpringApplicationRunListener ，重写 environmentPrepared 方法
自定义 EnvironmentPostProcessor
自定义 ApplicationListener 监听 ApplicationEnvironmentPreparedEvent 事件
ConfigFileApplicationListener，即是 EnvironmentPostProcessor ，又是 ApplicationListener ，类的层次结构如下
@Override
public void onApplicationEvent(ApplicationEvent event) {
// 处理 ApplicationEnvironmentPreparedEvent 事件
if (event instanceof ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent(
(ApplicationEnvironmentPreparedEvent) event);
}
// 处理 ApplicationPreparedEvent 事件
if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent(event);
}
}
private void onApplicationEnvironmentPreparedEvent(
ApplicationEnvironmentPreparedEvent event) {
// 加载 META-INF/spring.factories 中配置的 EnvironmentPostProcessor
List
// 加载自己 ConfigFileApplicationListener
postProcessors.add(this);
// 按照 Ordered 进行优先级排序
AnnotationAwareOrderComparator.sort(postProcessors);
// 回调 EnvironmentPostProcessor
for (EnvironmentPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessEnvironment(event.getEnvironment(), event.getSpringApplication());
}
}
List
return SpringFactoriesLoader.loadFactories(EnvironmentPostProcessor.class, getClass().getClassLoader());
}
@Override
public void
postProcessEnvironment(ConfigurableEnvironment environment,
SpringApplication application) {
addPropertySources(environment, application.getResourceLoader());
}
/**
* Add config file property sources to the specified environment.
* @param environment the environment to add source to
* @param resourceLoader the resource loader
* @see
#addPostProcessors(ConfigurableApplicationContext)
*/
protected void
addPropertySources(ConfigurableEnvironment environment,
ResourceLoader resourceLoader) {
RandomValuePropertySource.addToEnvironment(environment);
// 添加配置文件的属性源
new Loader(environment, resourceLoader).load();
}
RandomValuePropertySource
public static void
addToEnvironment(ConfigurableEnvironment environment) {
// 在 systemEnvironment 后面添加 random
environment.getPropertySources().addAfter(
StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
new RandomValuePropertySource(RANDOM_PROPERTY_SOURCE_NAME));
logger.trace("RandomValuePropertySource add to Environment");
}
添加配置文件的属性源：执行
new Loader(environment, resourceLoader).load();，
调用 load(Profile, DocumentFilterFactory, DocumentConsumer)（getSearchLocations()
获取配置文件位置，可以指定通过 spring.config.additional-location 、spring.config.location 、spring.config.name 参数或者使用默认值 ）， 然后调用 addLoadedPropertySources -> addLoadedPropertySource（加载 查找出来的 PropertySource 到 PropertySources，并确保放置到 defaultProperties 的前面 ）
默认的查找位置，配置为
"classpath:/,classpath:/config/,file:./,file:./config/"，查找顺序从后向前
PropertySources 顺序：
1. commandLineArgs
2. servletConfigInitParams
3. servletContextInitParams
4. jndiProperties
5. systemProperties
6. systemEnvironment
7. random
8. application.properties ...
9. defaultProperties
3
SpringApplication#prepareContext
prepareContext 方法中，主要的三步如下
private void
prepareContext(ConfigurableApplicationContext context,
ConfigurableEnvironment environment,
SpringApplicationRunListeners listeners,
ApplicationArguments applicationArguments,
Banner printedBanner) {
...
applyInitializers(context); // 3.1
listeners.contextPrepared(context); //3.2
...
listeners.contextLoaded(context); // 3.3
}
3.1、applyInitializers 方法
会遍历执行所有的 ApplicationContextInitializer#initialize
扩展点
自定义 ApplicationContextInitializer
3.2、listeners.contextPrepared 方法
会按优先级顺序遍历执行 SpringApplicationRunListener#contextPrepared，比如 EventPublishingRunListener 和 自定义的 SpringApplicationRunListener
扩展点
自定义 SpringApplicationRunListener ，重写 contextPrepared 方法
3.3、listeners.contextLoaded 方法
会按优先级顺序遍历执行 SpringApplicationRunListener#contextLoaded，比如 EventPublishingRunListener 和 自定义的 SpringApplicationRunListener
EventPublishingRunListener 发布
ApplicationPreparedEvent 事件
ConfigFileApplicationListener 监听
ApplicationEvent 事件 处理
ApplicationPreparedEvent 事件
扩展点
自定义 SpringApplicationRunListener ，重写 contextLoaded 方法
自定义 ApplicationListener ，监听 ApplicationPreparedEvent 事件
ConfigFileApplicationListener
@Override
public void onApplicationEvent(ApplicationEvent event) {
// 处理 ApplicationEnvironmentPreparedEvent 事件
if (event instanceof
ApplicationEnvironmentPreparedEvent) {
onApplicationEnvironmentPreparedEvent(
(ApplicationEnvironmentPreparedEvent) event);
}
// 处理 ApplicationPreparedEvent 事件
if (event instanceof ApplicationPreparedEvent) {
onApplicationPreparedEvent(event);
}
}
private void onApplicationPreparedEvent(ApplicationEvent event) {
this.logger.replayTo(ConfigFileApplicationListener.class);
addPostProcessors(((ApplicationPreparedEvent) event).getApplicationContext());
}
// 添加 PropertySourceOrderingPostProcessor 处理器，配置 PropertySources
protected void addPostProcessors(ConfigurableApplicationContext context) {
context.addBeanFactoryPostProcessor(
new PropertySourceOrderingPostProcessor(context));
}
PropertySourceOrderingPostProcessor
// 回调处理（在配置类属性源解析）
@Override
public void
postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
throws BeansException {
reorderSources(this.context.getEnvironment());
}
// 调整 PropertySources 顺序，先删除 defaultProperties， 再把 defaultProperties 添加到最后
private void reorderSources(ConfigurableEnvironment environment) {
PropertySource
.remove(DEFAULT_PROPERTIES);
if (defaultProperties != null) {
environment.getPropertySources().addLast(defaultProperties);
}
}
PropertySourceOrderingPostProcessor 是 BeanFactoryPostProcessor
4
SpringApplication#refreshContext
会进行 @Configuration 配置类属性源解析，处理 @PropertySource annotations on your @Configuration classes，但顺序是在 defaultProperties 之后，下面会把defaultProperties 调整到最后
AbstractApplicationContext#refresh 调用 invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors)， 然后进行 BeanFactoryPostProcessor 的回调处理 ，比如 PropertySourceOrderingPostProcessor 的回调（源码见上文）
PropertySources 顺序：
1. commandLineArgs
2. servletConfigInitParams
3. servletContextInitParams
4. jndiProperties
5. systemProperties
6. systemEnvironment
7. random
8. application.properties ...
9. @PropertySource annotations on your @Configuration classes
10. defaultProperties
不推荐使用这种方式，推荐使用在 refreshContext 之前准备好，@PropertySource 加载太晚，不会对自动配置产生任何影响
Part.2
扩展外部化配置属性源
1
基于 EnvironmentPostProcessor 扩展
public class CustomEnvironmentPostProcessor
implements EnvironmentPostProcessor
2
基于 ApplicationEnvironmentPreparedEvent 扩展
public class
ApplicationEnvironmentPreparedEventListener implements ApplicationListener
3
基于 SpringApplicationRunListener 扩展
public class CustomSpringApplicationRunListener implements SpringApplicationRunListener, Ordered
可以重写方法 environmentPrepared、contextPrepared、contextLoaded 进行扩展
4
基于 ApplicationContextInitializer 扩展
public class CustomApplicationContextInitializer implements ApplicationContextInitializer
关于与 Spring Cloud Config Client 整合，对外部化配置加载的扩展（绑定到Config Server，使用远端的property sources 初始化 Environment），参考源码PropertySourceBootstrapConfiguration（是对 ApplicationContextInitializer 的扩展）、ConfigServicePropertySourceLocator#locate
获取远端的property sources是 RestTemplate 通过向 http://{spring.cloud.config.uri}/{spring.application.name}/{spring.cloud.config.profile}/{spring.cloud.config.label} 发送 GET 请求方式获取的
5
基于 ApplicationPreparedEvent 扩展
public class ApplicationPreparedEventListener
implements ApplicationListener
6
扩展实战
6.1、扩展配置
在 classpath 下添加配置文件 META-INF/spring.factories， 内容如下
# Spring Application Run Listeners
org.springframework.boot.SpringApplicationRunListener=\
springboot.propertysource.extend.listener.CustomSpringApplicationRunListener
# Application Context Initializers
org.springframework.context.ApplicationContextInitializer=\
springboot.propertysource.extend.initializer.CustomApplicationContextInitializer
# Application Listeners
org.springframework.context.ApplicationListener=\
springboot.propertysource.extend.event.listener.ApplicationEnvironmentPreparedEventListener,\
springboot.propertysource.extend.event.listener.ApplicationPreparedEventListener
# Environment Post Processors
org.springframework.boot.env.EnvironmentPostProcessor=\
springboot.propertysource.extend.processor.CustomEnvironmentPostProcessor
以上的扩展可以选取其中一种进行扩展，只是属性源的加载时机不太一样
6.2、扩展实例代码
https://github.com/shijw823/springboot-externalized-configuration-extend.git
PropertySources 顺序：
propertySourceName: [ApplicationPreparedEventListener], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [CustomSpringApplicationRunListener-contextLoaded], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [CustomSpringApplicationRunListener-contextPrepared], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [CustomApplicationContextInitializer], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [bootstrapProperties], propertySourceClassName: [CompositePropertySource]
propertySourceName: [configurationProperties], propertySourceClassName: [ConfigurationPropertySourcesPropertySource]
propertySourceName: [CustomSpringApplicationRunListener-environmentPrepared], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [CustomEnvironmentPostProcessor-dev-application], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [ApplicationEnvironmentPreparedEventListener], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [commandLineArgs], propertySourceClassName: [SimpleCommandLinePropertySource]
propertySourceName: [servletConfigInitParams], propertySourceClassName: [StubPropertySource]
propertySourceName: [servletContextInitParams], propertySourceClassName: [ServletContextPropertySource]
propertySourceName: [systemProperties], propertySourceClassName: [MapPropertySource]
propertySourceName: [systemEnvironment], propertySourceClassName: [OriginAwareSystemEnvironmentPropertySource]
propertySourceName: [random], propertySourceClassName: [RandomValuePropertySource]
propertySourceName: [applicationConfig: [classpath:/extend/config/springApplicationRunListener.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [applicationConfig: [classpath:/extend/config/applicationListener.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [applicationConfig: [classpath:/extend/config/applicationContextInitializer.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [applicationConfig: [classpath:/extend/config/environmentPostProcessor.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [applicationConfig: [classpath:/extend/config/application.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [applicationConfig: [classpath:/extend/config/config.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [applicationConfig: [classpath:/application.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [springCloudClientHostInfo], propertySourceClassName: [MapPropertySource]
propertySourceName: [applicationConfig: [classpath:/bootstrap.properties]], propertySourceClassName: [OriginTrackedMapPropertySource]
propertySourceName: [propertySourceConfig], propertySourceClassName: [ResourcePropertySource]
propertySourceName: [defaultProperties], propertySourceClassName: [MapPropertySource]
bootstrapProperties 是 获取远端（config-server）的 property sources
加载顺序也可参考 http://{host}:{port}/actuator/env
PropertySources 单元测试顺序：
@TestPropertySource#properties
@SpringBootTest#properties
@TestPropertySource#locations
Part.3
参考资料
https://docs.spring.io/spring-boot/docs/2.0.5.RELEASE/reference/htmlsingle/#boot-features-external-config
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