Spring Boot外部化配置实战解析

太过爱你忘了你带给我的痛 2022-01-11 12:29 254阅读 0赞

## **一、流程分析** ##

### **1.1 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);
    
        }
    
        ...
    
    }

### **1.2 关键流程思维导图** ###

![Spring Boot外部化配置实战解析][Spring Boot]

### **1.3 关键流程详解** ###

对入口程序中标记的四步，分析如下

#### **1.3.1 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

![Spring Boot外部化配置实战解析][Spring Boot 1]

#### **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应用类型下，会创建 StandardServletEnvironment，本文以 StandardServletEnvironment 为例，类的层次结构如下

![Spring Boot外部化配置实战解析][Spring Boot 2]

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：**

*  servletConfigInitParams
 *  servletContextInitParams
 *  jndiProperties
 *  systemProperties
 *  systemEnvironment

PropertySources 与 PropertySource 关系为 1 对 N

##### **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：**

*  commandLineArgs
 *  servletConfigInitParams
 *  servletContextInitParams
 *  jndiProperties
 *  systemProperties
 *  systemEnvironment
 *  defaultProperties

##### **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

![Spring Boot外部化配置实战解析][Spring Boot 3]

@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：**

*  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** #####

会遍历执行所有的 ApplicationContextInitializer\#initialize

**扩展点**

*  自定义 ApplicationContextInitializer

##### **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）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

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

#### **1.3.4 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：**

*  commandLineArgs
 *  servletConfigInitParams
 *  servletContextInitParams
 *  jndiProperties
 *  systemProperties
 *  systemEnvironment
 *  random
 *  application.properties ...
 *  @PropertySource annotations on your @Configuration classes
 *  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）

## **二、扩展外部化配置属性源** ##

### **2.1 基于 EnvironmentPostProcessor 扩展** ###

public class CustomEnvironmentPostProcessor 
    
    implements EnvironmentPostProcessor

### **2.2 基于 ApplicationEnvironmentPreparedEvent 扩展** ###

public class 
    
    ApplicationEnvironmentPreparedEventListener implements ApplicationListener

### **2.3 基于 SpringApplicationRunListener 扩展** ###

public class CustomSpringApplicationRunListener implements SpringApplicationRunListener, Ordered

可以重写方法 environmentPrepared、contextPrepared、contextLoaded 进行扩展

### **2.4 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

### **2.5 基于 ApplicationPreparedEvent 扩展** ###

public class ApplicationPreparedEventListener 
    
    implements ApplicationListener

### **2.6 扩展实战** ###

#### **2.6.1 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

#### **2.6.2 扩展实例代码** ####

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

## **三、参考资料** ##

[https://docs.spring.io/spring-boot/docs/2.0.5.RELEASE/reference/htmlsingle/\#boot-features-external-config][https_docs.spring.io_spring-boot_docs_2.0.5.RELEASE_reference_htmlsingle_boot-features-external-config]

作者：石建伟

转载于:https://blog.51cto.com/14159827/2404096

[Spring Boot]: /images/20220110/8e77a74abef4443bac4e488f2766a7fe.png
[Spring Boot 1]: /images/20220110/e16c220e3b6a45b98f67d2d42acf1b40.png
[Spring Boot 2]: /images/20220110/e756b8031a5843d6945f41853dcef0a6.png
[Spring Boot 3]: /images/20220110/d8189248d7974837a55725181a704c8e.png
[https_github.com_shijw823_springboot-externalized-configuration-extend.git]: https://github.com/shijw823/springboot-externalized-configuration-extend.git
[https_docs.spring.io_spring-boot_docs_2.0.5.RELEASE_reference_htmlsingle_boot-features-external-config]: https://docs.spring.io/spring-boot/docs/2.0.5.RELEASE/reference/htmlsingle/#boot-features-external-config