Spring Boot 外部化配置實戰解析

宜信技術學院發表於2019-03-01

來源：宜信技術學院作者：石建偉

一、流程分析

入口程式

在 SpringApplication#run(String... args) 方法中，外部化配置關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);
    }
    ...
}
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關鍵流程思維導圖

關鍵流程詳解

對入口程式中標記的四步，分析如下

1、`SpringApplication#getRunListeners`

載入 META-INF/spring.factories 獲取 SpringApplicationRunListener 的例項集合，存放的物件是 EventPublishingRunListener 型別以及自定義的 SpringApplicationRunListener 實現型別

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;
}
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2.1、`getOrCreateEnvironment` 方法

在 WebApplicationType.SERVLET web應用型別下，會建立 StandardServletEnvironment，本文以 StandardServletEnvironment 為例，類的層次結構如下

當建立 StandardServletEnvironment ，StandardServletEnvironment 父類 AbstractEnvironment 呼叫 customizePropertySources 方法，會執行 StandardServletEnvironment#customizePropertySources 和 StandardEnvironment#customizePropertySources ，原始碼如下

AbstractEnvironment

public AbstractEnvironment() {
    customizePropertySources(this.propertySources);
    if (logger.isDebugEnabled()) {
        logger.debug("Initialized " + getClass().getSimpleName() + " with PropertySources " + this.propertySources);
    }
}
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StandardServletEnvironment#customizePropertySources

/** Servlet context init parameters property source name: {@value} */
public static final String SERVLET_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);
}
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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());
}
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PropertySources 順序：

servletConfigInitParams
servletContextInitParams
jndiProperties
systemProperties
systemEnvironment

PropertySources 與 PropertySource 關係為 1 對 N

2.2、`configureEnvironment` 方法

呼叫 configurePropertySources(environment, args)，在方法裡面設定 Environment 的 PropertySources ，包含 defaultProperties 和 SimpleCommandLinePropertySource （commandLineArgs），PropertySources 新增 defaultProperties 到最後，新增 SimpleCommandLinePropertySource （commandLineArgs）到最前面

PropertySources 順序：

commandLineArgs
servletConfigInitParams
servletContextInitParams
jndiProperties
systemProperties
systemEnvironment
defaultProperties

2.3、`listeners.environmentPrepared` 方法

會按優先順序順序遍歷執行 SpringApplicationRunListener#environmentPrepared，比如 EventPublishingRunListener 和自定義的 SpringApplicationRunListener

EventPublishingRunListener 釋出 ApplicationEnvironmentPreparedEvent 事件
- ConfigFileApplicationListener 監聽 ApplicationEvent 事件、處理 ApplicationEnvironmentPreparedEvent 事件，載入所有 EnvironmentPostProcessor 包括自己，然後按照順序進行方法回撥
  - ConfigFileApplicationListener#postProcessEnvironment 方法回撥，然後addPropertySources 方法呼叫 RandomValuePropertySource#addToEnvironment，在 systemEnvironment 後面新增 random，然後新增配置檔案的屬性源（詳見原始碼 ConfigFileApplicationListener.Loader#load()
擴充套件點
- 自定義 SpringApplicationRunListener ，重寫 environmentPrepared 方法
- 自定義 EnvironmentPostProcessor
- 自定義 ApplicationListener 監聽 ApplicationEnvironmentPreparedEvent 事件

ConfigFileApplicationListener，即是 EnvironmentPostProcessor ，又是 ApplicationListener ，類的層次結構如下

@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) {
    // 載入 META-INF/spring.factories 中配置的 EnvironmentPostProcessor
    List<EnvironmentPostProcessor> postProcessors = loadPostProcessors();
    // 載入自己 ConfigFileApplicationListener
    postProcessors.add(this);
    // 按照 Ordered 進行優先順序排序
    AnnotationAwareOrderComparator.sort(postProcessors);
    // 回撥 EnvironmentPostProcessor
    for (EnvironmentPostProcessor postProcessor : postProcessors) {
        postProcessor.postProcessEnvironment(event.getEnvironment(),
                                             event.getSpringApplication());
    }
}

List<EnvironmentPostProcessor> loadPostProcessors() {
    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);
    // 新增配置檔案的屬性源
    new Loader(environment, resourceLoader).load();
}
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RandomValuePropertySource

public static void addToEnvironment(ConfigurableEnvironment environment) {
    // 在 systemEnvironment 後面新增 random
    environment.getPropertySources().addAfter(
        StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
        new RandomValuePropertySource(RANDOM_PROPERTY_SOURCE_NAME));
    logger.trace("RandomValuePropertySource add to Environment");
}
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新增配置檔案的屬性源：

執行 new Loader(environment, resourceLoader).load(); ，呼叫 load(Profile, DocumentFilterFactory, DocumentConsumer) （getSearchLocations() 獲取配置檔案位置，可以指定通過 spring.config.additional-location 、spring.config.location 、spring.config.name 引數或者使用預設值），然後呼叫 addLoadedPropertySources -> addLoadedPropertySource（載入查詢出來的 PropertySource 到 PropertySources，並確保放置到 defaultProperties 的前面）

預設的查詢位置，配置為 "classpath:/,classpath:/config/,file:./,file:./config/" ，查詢順序從後向前

PropertySources 順序：

commandLineArgs
servletConfigInitParams
servletContextInitParams
jndiProperties
systemProperties
systemEnvironment
random
application.properties …
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
}
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3.1、`applyInitializers` 方法

會遍歷執行所有的 ApplicationContextInitializer#initialize

擴充套件點
- 自定義 ApplicationContextInitializer

3.2、`listeners.contextPrepared` 方法

會按優先順序順序遍歷執行 SpringApplicationRunListener#contextPrepared，比如 EventPublishingRunListener 和自定義的 SpringApplicationRunListener

擴充套件點
- 自定義 SpringApplicationRunListener ，重寫 contextPrepared 方法

3.3、`listeners.contextLoaded` 方法

會按優先順序順序遍歷執行 SpringApplicationRunListener#contextLoaded，比如 EventPublishingRunListener 和自定義的 SpringApplicationRunListener

EventPublishingRunListener 釋出 ApplicationPreparedEvent 事件
- ConfigFileApplicationListener 監聽 ApplicationEvent 事件處理 ApplicationPreparedEvent 事件
擴充套件點
- 自定義 SpringApplicationRunListener ，重寫 contextLoaded 方法
- 自定義 ApplicationListener ，監聽 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());
}

// 新增 PropertySourceOrderingPostProcessor 處理器，配置 PropertySources
protected void addPostProcessors(ConfigurableApplicationContext context) {
    context.addBeanFactoryPostProcessor(
        new PropertySourceOrderingPostProcessor(context));
}
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PropertySourceOrderingPostProcessor

// 回撥處理（在配置類屬性源解析）
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
    throws BeansException {
    reorderSources(this.context.getEnvironment());
}

// 調整 PropertySources 順序，先刪除 defaultProperties， 再把 defaultProperties 新增到最後
private void reorderSources(ConfigurableEnvironment environment) {
    PropertySource<?> defaultProperties = environment.getPropertySources()
        .remove(DEFAULT_PROPERTIES);
    if (defaultProperties != null) {
        environment.getPropertySources().addLast(defaultProperties);
    }
}
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PropertySourceOrderingPostProcessor 是 BeanFactoryPostProcessor

4、`SpringApplication#refreshContext`

會進行 @Configuration 配置類屬性源解析，處理 @PropertySource annotations on your @Configuration classes，但順序是在 defaultProperties 之後，下面會把 defaultProperties 調整到最後

AbstractApplicationContext#refresh 呼叫 invokeBeanFactoryPostProcessors (PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors)，然後進行 BeanFactoryPostProcessor 的回撥處理，比如 PropertySourceOrderingPostProcessor 的回撥（原始碼見上文）

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 之前準備好，@PropertySource 載入太晚，不會對自動配置產生任何影響

二、擴充套件外部化配置屬性源

1、基於 `EnvironmentPostProcessor` 擴充套件

public class CustomEnvironmentPostProcessor implements EnvironmentPostProcessor
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2、基於 `ApplicationEnvironmentPreparedEvent` 擴充套件

public class ApplicationEnvironmentPreparedEventListener implements ApplicationListener<ApplicationEnvironmentPreparedEvent>
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3、基於 `SpringApplicationRunListener` 擴充套件

public class CustomSpringApplicationRunListener implements SpringApplicationRunListener, Ordered
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可以重寫方法 environmentPrepared、contextPrepared、contextLoaded 進行擴充套件

4、基於 `ApplicationContextInitializer` 擴充套件

public class CustomApplicationContextInitializer implements ApplicationContextInitializer
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關於與 Spring Cloud Config Client 整合，對外部化配置載入的擴充套件（繫結到Config Server，使用遠端的property sources 初始化 Environment），參考原始碼
PropertySourceBootstrapConfiguration（是對 ApplicationContextInitializer 的擴充套件）、ConfigServicePropertySourceLocator#locate

獲取遠端的property sources是 RestTemplate 通過向 http://{spring.cloud.config.uri}/{spring.application.name}/{spring.cloud.config.profile}/{spring.cloud.config.label} 傳送 GET 請求方式獲取的

5、基於 `ApplicationPreparedEvent` 擴充套件

public class ApplicationPreparedEventListener implements ApplicationListener<ApplicationPreparedEvent>
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6、擴充套件實戰

6.1、擴充套件配置

在 classpath 下新增配置檔案 META-INF/spring.factories，內容如下

# 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
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以上的擴充套件可以選取其中一種進行擴充套件，只是屬性源的載入時機不太一樣

6.2、擴充套件例項程式碼

github.com/shijw823/sp…

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]
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bootstrapProperties 是獲取遠端（config-server）的 property sources

載入順序也可參考 http://{host}:{port}/actuator/env

PropertySources 單元測試順序：

@TestPropertySource#properties
@SpringBootTest#properties
@TestPropertySource#locations
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三、參考資料

docs.spring.io/spring-boot…

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2022-02-25
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Spring Boot 外部化配置實戰解析

一、流程分析

入口程式

關鍵流程思維導圖

關鍵流程詳解

1、SpringApplication#getRunListeners

2、SpringApplication#prepareEnvironment

2.1、getOrCreateEnvironment 方法

2.2、configureEnvironment 方法

2.3、listeners.environmentPrepared 方法

3、SpringApplication#prepareContext

3.1、applyInitializers 方法

3.2、listeners.contextPrepared 方法

3.3、listeners.contextLoaded 方法

4、SpringApplication#refreshContext

二、擴充套件外部化配置屬性源

1、基於 EnvironmentPostProcessor 擴充套件

2、基於 ApplicationEnvironmentPreparedEvent 擴充套件

3、基於 SpringApplicationRunListener 擴充套件

4、基於 ApplicationContextInitializer 擴充套件

5、基於 ApplicationPreparedEvent 擴充套件

6、擴充套件實戰

6.1、擴充套件配置

6.2、擴充套件例項程式碼

三、參考資料

相關文章

1、`SpringApplication#getRunListeners`

2、`SpringApplication#prepareEnvironment`

2.1、`getOrCreateEnvironment` 方法

2.2、`configureEnvironment` 方法

2.3、`listeners.environmentPrepared` 方法

3、`SpringApplication#prepareContext`

3.1、`applyInitializers` 方法

3.2、`listeners.contextPrepared` 方法

3.3、`listeners.contextLoaded` 方法

4、`SpringApplication#refreshContext`

1、基於 `EnvironmentPostProcessor` 擴充套件

2、基於 `ApplicationEnvironmentPreparedEvent` 擴充套件

3、基於 `SpringApplicationRunListener` 擴充套件

4、基於 `ApplicationContextInitializer` 擴充套件

5、基於 `ApplicationPreparedEvent` 擴充套件