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Spring Boot 外部化配置实战解析

2018-10-30 14:45 603 查看

来源：宜信技术学院 作者：石建伟

一、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

![](Spring Boot 外部化配置关键流程.png)

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 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);
}

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<EnvironmentPostProcessor> postProcessors = loadPostProcessors();
// 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<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);
// 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<?> defaultProperties = environment.getPropertySources()
.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

    二、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<ApplicationEnvironmentPreparedEvent>

    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<ApplicationPreparedEvent>

    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

    三、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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