Spring Boot外部化配置實(shí)戰(zhàn)解析

一、流程分析

1.1 入口程序

在 SpringApplication#run(String... args) 方法中，外部化配置關(guān)鍵流程分為以下四步

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);

    }

    ...

}

1.2 關(guān)鍵流程思維導(dǎo)圖

1.3 關(guān)鍵流程詳解

對(duì)入口程序中標(biāo)記的四步，分析如下

1.3.1 SpringApplication#getRunListeners

加載 META-INF/spring.factories

獲取 SpringApplicationRunListener

的實(shí)例集合，存放的對(duì)象是 EventPublishingRunListener 類型 以及自定義的 SpringApplicationRunListener 實(shí)現(xiàn)類型

1.3.2 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;

}

1) getOrCreateEnvironment 方法

在 WebApplicationType.SERVLET web應(yīng)用類型下，會(huì)創(chuàng)建 StandardServletEnvironment，本文以 StandardServletEnvironment 為例，類的層次結(jié)構(gòu)如下

當(dāng)創(chuàng)建 StandardServletEnvironment，StandardServletEnvironment 父類 AbstractEnvironment 調(diào)用 customizePropertySources 方法，會(huì)執(zhí)行 StandardServletEnvironment#customizePropertySources和 StandardEnvironment#customizePropertySources ，源碼如下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 順序：

• servletConfigInitParams

• servletContextInitParams

• jndiProperties

• systemProperties

• systemEnvironment

PropertySources 與 PropertySource 關(guān)系為 1 對(duì) N

2) configureEnvironment 方法

調(diào)用 configurePropertySources(environment, args)， 在方法里面設(shè)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 順序：

• commandLineArgs

• servletConfigInitParams

• servletContextInitParams

• jndiProperties

• systemProperties

• systemEnvironment

• defaultProperties

3) listeners.environmentPrepared 方法

會(huì)按優(yōu)先級(jí)順序遍歷執(zhí)行 SpringApplicationRunListener#environmentPrepared，比如 EventPublishingRunListener 和 自定義的 SpringApplicationRunListener

EventPublishingRunListener 發(fā)布

ApplicationEnvironmentPreparedEvent 事件

• ConfigFileApplicationListener 監(jiān)聽(tīng)

ApplicationEvent 事件 、處理 ApplicationEnvironmentPreparedEvent 事件，加載所有 EnvironmentPostProcessor 包括自己，然后按照順序進(jìn)行方法回調(diào)

---ConfigFileApplicationListener#postProcessEnvironment方法回調(diào) ，然后addPropertySources 方法調(diào)用

RandomValuePropertySource#addToEnvironment，在 systemEnvironment 后面添加 random，然后添加配置文件的屬性源（詳見(jiàn)源碼ConfigFileApplicationListener.Loader#load()

擴(kuò)展點(diǎn)

• 自定義 SpringApplicationRunListener ，重寫(xiě) environmentPrepared 方法

• 自定義 EnvironmentPostProcessor

• 自定義 ApplicationListener 監(jiān)聽(tīng) ApplicationEnvironmentPreparedEvent 事件

• ConfigFileApplicationListener，即是 EnvironmentPostProcessor ，又是 ApplicationListener ，類的層次結(jié)構(gòu)如下

@Override

public void onApplicationEvent(ApplicationEvent event) {

    // 處理 ApplicationEnvironmentPreparedEvent 事件

    if (event instanceof ApplicationEnvironmentPreparedEvent) {

        onApplicationEnvironmentPreparedEvent(

            (ApplicationEnvironmentPreparedEvent) event);

    }

    // 處理 ApplicationPreparedEvent 事件

    if (event instanceof ApplicationPreparedEvent) {

        onApplicationPreparedEvent(event);

    }

}

private void onApplicationEnvironmentPreparedEvent(

    ApplicationEnvironmentPreparedEvent event) {

    // 加載 META-INF/spring.factories 中配置的 EnvironmentPostProcessor

    List

    // 加載自己 ConfigFileApplicationListener

    postProcessors.add(this);

    // 按照 Ordered 進(jìn)行優(yōu)先級(jí)排序

    AnnotationAwareOrderComparator.sort(postProcessors);

    // 回調(diào) 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);

    // 添加配置文件的屬性源

    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");

}

添加配置文件的屬性源：執(zhí)行

new Loader(environment, resourceLoader).load();，

調(diào)用 load(Profile, DocumentFilterFactory, DocumentConsumer)（getSearchLocations()

獲取配置文件位置，可以指定通過(guò) spring.config.additional-location 、spring.config.location 、spring.config.name 參數(shù)或者使用默認(rèn)值 ）， 然后調(diào)用 addLoadedPropertySources -> addLoadedPropertySource（加載 查找出來(lái)的 PropertySource 到 PropertySources，并確保放置到 defaultProperties 的前面 ）

默認(rèn)的查找位置，配置為

"classpath:/,classpath:/config/,file:./,file:./config/"，查找順序從后向前

PropertySources 順序：

• commandLineArgs

• servletConfigInitParams

• servletContextInitParams

• jndiProperties

• systemProperties

• systemEnvironment

• random

• application.properties ...

• defaultProperties

1.3.3 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

}

1）applyInitializers 方法

會(huì)遍歷執(zhí)行所有的 ApplicationContextInitializer#initialize

擴(kuò)展點(diǎn)

• 自定義 ApplicationContextInitializer

2）listeners.contextPrepared 方法

會(huì)按優(yōu)先級(jí)順序遍歷執(zhí)行 SpringApplicationRunListener#contextPrepared，比如 EventPublishingRunListener 和 自定義的 SpringApplicationRunListener

擴(kuò)展點(diǎn)

自定義 SpringApplicationRunListener ，重寫(xiě) contextPrepared 方法

3）listeners.contextLoaded 方法

會(huì)按優(yōu)先級(jí)順序遍歷執(zhí)行 SpringApplicationRunListener#contextLoaded，比如 EventPublishingRunListener 和 自定義的 SpringApplicationRunListener

EventPublishingRunListener 發(fā)布

ApplicationPreparedEvent 事件

• ConfigFileApplicationListener 監(jiān)聽(tīng)

ApplicationEvent 事件 處理

ApplicationPreparedEvent 事件

擴(kuò)展點(diǎn)

• 自定義 SpringApplicationRunListener ，重寫(xiě) contextLoaded 方法

• 自定義 ApplicationListener ，監(jiān)聽(tīng) ApplicationPreparedEvent 事件

ConfigFileApplicationListener

@Override

public void onApplicationEvent(ApplicationEvent event) {

    // 處理 ApplicationEnvironmentPreparedEvent 事件

    if (event instanceof 

ApplicationEnvironmentPreparedEvent) {

        onApplicationEnvironmentPreparedEvent(

            (ApplicationEnvironmentPreparedEvent) event);

    }

    // 處理 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 處理器，配置 PropertySources

protected void addPostProcessors(ConfigurableApplicationContext context) {

    context.addBeanFactoryPostProcessor(

        new PropertySourceOrderingPostProcessor(context));

}

PropertySourceOrderingPostProcessor

// 回調(diào)處理（在配置類屬性源解析）

@Override

public void 

postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)

    throws BeansException {

    reorderSources(this.context.getEnvironment());

}

// 調(diào)整 PropertySources 順序，先刪除 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

1.3.4 SpringApplication#refreshContext

會(huì)進(jìn)行 @Configuration 配置類屬性源解析，處理 @PropertySource annotations on your @Configuration classes，但順序是在 defaultProperties 之后，下面會(huì)把defaultProperties 調(diào)整到最后

AbstractApplicationContext#refresh 調(diào)用 invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors)， 然后進(jìn)行 BeanFactoryPostProcessor 的回調(diào)處理 ，比如 PropertySourceOrderingPostProcessor 的回調(diào)（源碼見(jiàn)上文）

PropertySources 順序：

• commandLineArgs

• servletConfigInitParams

• servletContextInitParams

• jndiProperties

• systemProperties

• systemEnvironment

• random

• application.properties ...

• @PropertySource annotations on your @Configuration classes

• defaultProperties

（不推薦使用這種方式，推薦使用在 refreshContext 之前準(zhǔn)備好，@PropertySource 加載太晚，不會(huì)對(duì)自動(dòng)配置產(chǎn)生任何影響）

二、擴(kuò)展外部化配置屬性源

2.1 基于 EnvironmentPostProcessor 擴(kuò)展

public class CustomEnvironmentPostProcessor 

implements EnvironmentPostProcessor

2.2 基于 ApplicationEnvironmentPreparedEvent 擴(kuò)展

public class 

ApplicationEnvironmentPreparedEventListener implements ApplicationListener

2.3 基于 SpringApplicationRunListener 擴(kuò)展

public class CustomSpringApplicationRunListener implements SpringApplicationRunListener, Ordered

可以重寫(xiě)方法 environmentPrepared、contextPrepared、contextLoaded 進(jìn)行擴(kuò)展

2.4 基于 ApplicationContextInitializer 擴(kuò)展

public class CustomApplicationContextInitializer implements ApplicationContextInitializer

關(guān)于與 Spring Cloud Config Client 整合，對(duì)外部化配置加載的擴(kuò)展（綁定到Config Server，使用遠(yuǎn)端的property sources 初始化 Environment），參考源碼PropertySourceBootstrapConfiguration（是對(duì) ApplicationContextInitializer 的擴(kuò)展）、ConfigServicePropertySourceLocator#locate

獲取遠(yuǎn)端的property sources是 RestTemplate 通過(guò)向 http://{spring.cloud.config.uri}/{spring.application.name}/{spring.cloud.config.profile}/{spring.cloud.config.label} 發(fā)送 GET 請(qǐng)求方式獲取的

2.5 基于 ApplicationPreparedEvent 擴(kuò)展

public class ApplicationPreparedEventListener 

implements ApplicationListener

2.6 擴(kuò)展實(shí)戰(zhàn)

2.6.1 擴(kuò)展配置

在 classpath 下添加配置文件 META-INF/spring.factories， 內(nèi)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

以上的擴(kuò)展可以選取其中一種進(jìn)行擴(kuò)展，只是屬性源的加載時(shí)機(jī)不太一樣

2.6.2 擴(kuò)展實(shí)例代碼

https://github.com/shijw823/springboot-externalized-configuration-extend.git

PropertySources 順序：

• 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 獲取遠(yuǎn)端（config-server）的 property sources

加載順序也可參考 http://{host}:{port}/actuator/env

PropertySources 單元測(cè)試順序：

• @TestPropertySource#properties

• @SpringBootTest#properties

• @TestPropertySource#locations

三、參考資料

https://docs.spring.io/spring-boot/docs/2.0.5.RELEASE/reference/htmlsingle/#boot-features-external-config

作者：石建偉