SpringBoot源码阅读(10)——后处理器

后处理器是在监听器EnvironmentPostProcessorApplicationListener中被加载。
入口在SpringApplication实例方法prepareEnvironment，第343行。

listeners.environmentPrepared(bootstrapContext, environment);

这里触发了事件ApplicationEnvironmentPreparedEvent
相关监听器

监听器	Order
DelegatingApplicationListener	0
EnvironmentPostProcessorApplicationListener	Integer.MIN_VALUE + 10
LoggingApplicationListener	Integer.MIN_VALUE + 20
AnsiOutputApplicationListener	Integer.MIN_VALUE + 11
FileEncodingApplicationListener	Integer.MAX_VALUE

排序后，触发顺序

1. DelegatingApplicationListener
2. EnvironmentPostProcessorApplicationListener
3. AnsiOutputApplicationListener
4. LoggingApplicationListener
5. FileEncodingApplicationListener

EnvironmentPostProcessorApplicationListener 就是监听器之一。

EnvironmentPostProcessorApplicationListener

主要方法

private void onApplicationEnvironmentPreparedEvent(ApplicationEnvironmentPreparedEvent event) {ConfigurableEnvironment environment = event.getEnvironment();SpringApplication application = event.getSpringApplication();for (EnvironmentPostProcessor postProcessor : getEnvironmentPostProcessors(application.getResourceLoader(),event.getBootstrapContext())) {postProcessor.postProcessEnvironment(environment, application);}
}

List<EnvironmentPostProcessor> getEnvironmentPostProcessors(ResourceLoader resourceLoader,ConfigurableBootstrapContext bootstrapContext) {ClassLoader classLoader = (resourceLoader != null) ? resourceLoader.getClassLoader() : null;EnvironmentPostProcessorsFactory postProcessorsFactory = this.postProcessorsFactory.apply(classLoader);return postProcessorsFactory.getEnvironmentPostProcessors(this.deferredLogs, bootstrapContext);
}

其中this.postProcessorsFactory是EnvironmentPostProcessorsFactory::fromSpringFactories

static EnvironmentPostProcessorsFactory fromSpringFactories(ClassLoader classLoader) {return new ReflectionEnvironmentPostProcessorsFactory(classLoader,SpringFactoriesLoader.loadFactoryNames(EnvironmentPostProcessor.class, classLoader));
}

EnvironmentPostProcessor的实现类

# Environment Post Processors
org.springframework.boot.env.EnvironmentPostProcessor=\
org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor,\
org.springframework.boot.env.RandomValuePropertySourceEnvironmentPostProcessor,\
org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor,\
org.springframework.boot.env.SystemEnvironmentPropertySourceEnvironmentPostProcessor,\
org.springframework.boot.reactor.DebugAgentEnvironmentPostProcessor# Environment Post Processors
org.springframework.boot.env.EnvironmentPostProcessor=\
org.springframework.boot.autoconfigure.integration.IntegrationPropertiesEnvironmentPostProcessor

处理器	Order值
CloudFoundryVcapEnvironmentPostProcessor	Integer.MIN_VALUE + 10 - 1
ConfigDataEnvironmentPostProcessor	Integer.MIN_VALUE + 10
RandomValuePropertySourceEnvironmentPostProcessor	Integer.MIN_VALUE + 1
SpringApplicationJsonEnvironmentPostProcessor	Integer.MIN_VALUE + 5
SystemEnvironmentPropertySourceEnvironmentPostProcessor	Integer.MIN_VALUE + 5 - 1
DebugAgentEnvironmentPostProcessor	Integer.MAX_VALUE
IntegrationPropertiesEnvironmentPostProcessor	Integer.MAX_VALUE

最后顺序

1. RandomValuePropertySourceEnvironmentPostProcessor
2. SystemEnvironmentPropertySourceEnvironmentPostProcessor
3. SpringApplicationJsonEnvironmentPostProcessor
4. CloudFoundryVcapEnvironmentPostProcessor
5. ConfigDataEnvironmentPostProcessor
6. DebugAgentEnvironmentPostProcessor
7. IntegrationPropertiesEnvironmentPostProcessor

EnvironmentPostProcessorApplicationListener实例化的时候，是调用的无参构造方法。

public EnvironmentPostProcessorApplicationListener() {this(EnvironmentPostProcessorsFactory::fromSpringFactories, new DeferredLogs());
}

实例化后关键属性

属性	值
postProcessorsFactory	EnvironmentPostProcessorsFactory::fromSpringFactories
deferredLogs	DeferredLogFactory

ReflectionEnvironmentPostProcessorsFactory

实例化后的属性

属性	值
classes	null
classLoader	null
classNames	EnvironmentPostProcessor实现类的类全限定名\

加载EnvironmentPostProcessor实现类的主要逻辑

@Override
public List<EnvironmentPostProcessor> getEnvironmentPostProcessors(DeferredLogFactory logFactory,ConfigurableBootstrapContext bootstrapContext) {Instantiator<EnvironmentPostProcessor> instantiator = new Instantiator<>(EnvironmentPostProcessor.class,(parameters) -> {parameters.add(DeferredLogFactory.class, logFactory);parameters.add(Log.class, logFactory::getLog);parameters.add(ConfigurableBootstrapContext.class, bootstrapContext);parameters.add(BootstrapContext.class, bootstrapContext);parameters.add(BootstrapRegistry.class, bootstrapContext);});return (this.classes != null) ? instantiator.instantiateTypes(this.classes): instantiator.instantiate(this.classLoader, this.classNames);
}

public Instantiator(Class<?> type, Consumer<AvailableParameters> availableParameters) {this(type, availableParameters, throwingFailureHandler);
}
public Instantiator(Class<?> type, Consumer<AvailableParameters> availableParameters,FailureHandler failureHandler) {this.type = type;this.availableParameters = getAvailableParameters(availableParameters);this.failureHandler = failureHandler;
}

Instantiator是一个通过用的实例化工具类。
主要逻辑：

1. 获取要实例化的类的构造方法，按照构造方法的参数个数倒序排序。
2. 然后检查每个参数，是否是给定参数集合中类的子类或者类本身。
3. 如果找到了，就把给定参数集合中的值作为参数返回，拿去调用构造方法
4. 优先使用个数多个的构造方法，默认使用无参构造
5. 构造完成后，使用AnnotationAwareOrderComparator比较器排序一番。

属性	值
type	EnvironmentPostProcessor.class
availableParameters	DeferredLogFactory.class factoryType -> DeferredLogs
Log.class	logFactory::getLog
ConfigurableBootstrapContext.class	factoryType -> bootstrapContext
BootstrapContext.class	factoryType -> bootstrapContext
BootstrapRegistry.class	factoryType -> bootstrapContext
failureHandler	初始化失败后的处理器,默认是抛异常

RandomValuePropertySourceEnvironmentPostProcessor

构造方法

public RandomValuePropertySourceEnvironmentPostProcessor(Log logger) {this.logger = logger;
}

SystemEnvironmentPropertySourceEnvironmentPostProcessor

默认无参构造

SpringApplicationJsonEnvironmentPostProcessor

默认无参构造

CloudFoundryVcapEnvironmentPostProcessor

构造方法

public CloudFoundryVcapEnvironmentPostProcessor(Log logger) {this.logger = logger;
}

ConfigDataEnvironmentPostProcessor

构造方法

public ConfigDataEnvironmentPostProcessor(DeferredLogFactory logFactory,ConfigurableBootstrapContext bootstrapContext) {this(logFactory, bootstrapContext, null);
}public ConfigDataEnvironmentPostProcessor(DeferredLogFactory logFactory,ConfigurableBootstrapContext bootstrapContext,ConfigDataEnvironmentUpdateListener environmentUpdateListener) {this.logFactory = logFactory;this.logger = logFactory.getLog(getClass());this.bootstrapContext = bootstrapContext;this.environmentUpdateListener = environmentUpdateListener;
}

DebugAgentEnvironmentPostProcessor

默认无参构造

IntegrationPropertiesEnvironmentPostProcessor

默认无参构造

最后得到各自的构造方法

类	构造方法
RandomValuePropertySourceEnvironmentPostProcessor	public RandomValuePropertySourceEnvironmentPostProcessor(Log logger)
SystemEnvironmentPropertySourceEnvironmentPostProcessor	无参构造
SpringApplicationJsonEnvironmentPostProcessor	无参构造
CloudFoundryVcapEnvironmentPostProcessor	public CloudFoundryVcapEnvironmentPostProcessor(Log logger)
ConfigDataEnvironmentPostProcessor	public ConfigDataEnvironmentPostProcessor(DeferredLogFactory logFactoryConfigurableBootstrapContext bootstrapContext)
DebugAgentEnvironmentPostProcessor	无参构造
IntegrationPropertiesEnvironmentPostProcessor	无参构造
实例化后排序

1. RandomValuePropertySourceEnvironmentPostProcessor
2. SystemEnvironmentPropertySourceEnvironmentPostProcessor
3. SpringApplicationJsonEnvironmentPostProcessor
4. CloudFoundryVcapEnvironmentPostProcessor
5. ConfigDataEnvironmentPostProcessor
6. DebugAgentEnvironmentPostProcessor
7. IntegrationPropertiesEnvironmentPostProcessor

逻辑

RandomValuePropertySourceEnvironmentPostProcessor

@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {RandomValuePropertySource.addToEnvironment(environment, this.logger);
}

这个处理器会创建一个Random对象，放入sources，key为random
如果环境变量已经加载，就放在环境变量后面，没有加载，就放到最后

SystemEnvironmentPropertySourceEnvironmentPostProcessor

@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {String sourceName = StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME;PropertySource<?> propertySource = environment.getPropertySources().get(sourceName);if (propertySource != null) {replacePropertySource(environment, sourceName, propertySource, application.getEnvironmentPrefix());}
}@SuppressWarnings("unchecked")
private void replacePropertySource(ConfigurableEnvironment environment, String sourceName,PropertySource<?> propertySource, String environmentPrefix) {Map<String, Object> originalSource = (Map<String, Object>) propertySource.getSource();SystemEnvironmentPropertySource source = new OriginAwareSystemEnvironmentPropertySource(sourceName,originalSource, environmentPrefix);environment.getPropertySources().replace(sourceName, source);
}

这个处理器会处理系统环境变量，把系统环境变量包装成OriginAwareSystemEnvironmentPropertySource

SpringApplicationJsonEnvironmentPostProcessor

@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {MutablePropertySources propertySources = environment.getPropertySources();propertySources.stream().map(JsonPropertyValue::get).filter(Objects::nonNull).findFirst().ifPresent((v) -> processJson(environment, v));
}
private void processJson(ConfigurableEnvironment environment, JsonPropertyValue propertyValue) {JsonParser parser = JsonParserFactory.getJsonParser();Map<String, Object> map = parser.parseMap(propertyValue.getJson());if (!map.isEmpty()) {addJsonPropertySource(environment, new JsonPropertySource(propertyValue, flatten(map)));}
}
public static JsonParser getJsonParser() {if (ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", null)) {return new JacksonJsonParser();}if (ClassUtils.isPresent("com.google.gson.Gson", null)) {return new GsonJsonParser();}if (ClassUtils.isPresent("org.yaml.snakeyaml.Yaml", null)) {return new YamlJsonParser();}return new BasicJsonParser();
}

这个处理器会从环境变量中获取spring.application.json或者SPRING_APPLICATION_JSON的配置，然后找到第一个配置，使用json解析器解析，放入source，名称为spring.application.json，位置在servletContextInitParams或者servletConfigInitParams之前。

CloudFoundryVcapEnvironmentPostProcessor

@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {if (CloudPlatform.CLOUD_FOUNDRY.isActive(environment)) {Properties properties = new Properties();JsonParser jsonParser = JsonParserFactory.getJsonParser();addWithPrefix(properties, getPropertiesFromApplication(environment, jsonParser), "vcap.application.");addWithPrefix(properties, getPropertiesFromServices(environment, jsonParser), "vcap.services.");MutablePropertySources propertySources = environment.getPropertySources();if (propertySources.contains(CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME)) {propertySources.addAfter(CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME,new PropertiesPropertySource("vcap", properties));}else {propertySources.addFirst(new PropertiesPropertySource("vcap", properties));}}
}

这个处理器，会从环境变量获取spring.main.cloud-platform的值，如果是CloudPlatform.CLOUD_FOUNDRY类型，如果值是CLOUD_FOUNDRY或者包含VCAP_APPLICATION或VCAP_SERVICES，就执行开源云平台的逻辑。
从环境变量中获取VCAP_APPLICATION 和VCAP_SERVICES的值，用json解析器解析，分别加上前缀vcap.application.和vcap.services.，放入sources，名称是vcap，位置上，如果有命令行参数，就放在命令行参数后面，如果没有，就放首位。

ConfigDataEnvironmentPostProcessor

@Override
public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {postProcessEnvironment(environment, application.getResourceLoader(), application.getAdditionalProfiles());
}

ConfigDataEnvironment getConfigDataEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader,Collection<String> additionalProfiles) {return new ConfigDataEnvironment(this.logFactory, this.bootstrapContext, environment, resourceLoader,additionalProfiles, this.environmentUpdateListener);
}

创建一个ConfigDataEnvironment实例，过程中会创建一个ConfigDataLocationResolvers实例。

ConfigDataEnvironment(DeferredLogFactory logFactory, ConfigurableBootstrapContext bootstrapContext,ConfigurableEnvironment environment, ResourceLoader resourceLoader, Collection<String> additionalProfiles,ConfigDataEnvironmentUpdateListener environmentUpdateListener) {Binder binder = Binder.get(environment);UseLegacyConfigProcessingException.throwIfRequested(binder);this.logFactory = logFactory;this.logger = logFactory.getLog(getClass());this.notFoundAction = binder.bind(ON_NOT_FOUND_PROPERTY, ConfigDataNotFoundAction.class).orElse(ConfigDataNotFoundAction.FAIL);this.bootstrapContext = bootstrapContext;this.environment = environment;this.resolvers = createConfigDataLocationResolvers(logFactory, bootstrapContext, binder, resourceLoader);this.additionalProfiles = additionalProfiles;this.environmentUpdateListener = (environmentUpdateListener != null) ? environmentUpdateListener: ConfigDataEnvironmentUpdateListener.NONE;this.loaders = new ConfigDataLoaders(logFactory, bootstrapContext, resourceLoader.getClassLoader());this.contributors = createContributors(binder);
}

感觉像是捅了马蜂窝了。
ConfigDataLocationResolvers实例化，会加载ConfigDataLocationResolver的实现类。

# ConfigData Location Resolvers
org.springframework.boot.context.config.ConfigDataLocationResolver=\
org.springframework.boot.context.config.ConfigTreeConfigDataLocationResolver,\
org.springframework.boot.context.config.StandardConfigDataLocationResolver

ConfigTreeConfigDataLocationResolver实例化，会创建LocationResourceLoader实例
StandardConfigDataLocationResolver实例化，会加载PropertySourceLoader的实现类

# PropertySource Loaders
org.springframework.boot.env.PropertySourceLoader=\
org.springframework.boot.env.PropertiesPropertySourceLoader,\
org.springframework.boot.env.YamlPropertySourceLoader

StandardConfigDataLocationResolver中会设置应用的配置文件名称，key是spring.config.name，默认值是application，也就是Spring配置文件的名字也是可以配置的，这个名字中不能包含*号。
至于PropertiesPropertySourceLoader和YamlPropertySourceLoader，就是解析Spring配置文件的两个加载器，前者解析properties后缀文件，后者解析yml后缀文件。
ConfigDataLocationResolvers中，在加载完成ConfigDataLocationResolver的接口后，会重新排序，把StandardConfigDataLocationResolver的子类或本身保留最后实现，放入集合末尾。

ConfigDataEnvironment实例化时，会创建ConfigDataLoaders实例，进而加载ConfigDataLoader的实例。

# ConfigData Loaders
org.springframework.boot.context.config.ConfigDataLoader=\
org.springframework.boot.context.config.ConfigTreeConfigDataLoader,\
org.springframework.boot.context.config.StandardConfigDataLoader

然后调用processAndApply，会读取配置文件。

void processAndApply() {ConfigDataImporter importer = new ConfigDataImporter(this.logFactory, this.notFoundAction, this.resolvers,this.loaders);registerBootstrapBinder(this.contributors, null, DENY_INACTIVE_BINDING);ConfigDataEnvironmentContributors contributors = processInitial(this.contributors, importer);ConfigDataActivationContext activationContext = createActivationContext(contributors.getBinder(null, BinderOption.FAIL_ON_BIND_TO_INACTIVE_SOURCE));contributors = processWithoutProfiles(contributors, importer, activationContext);activationContext = withProfiles(contributors, activationContext);contributors = processWithProfiles(contributors, importer, activationContext);applyToEnvironment(contributors, activationContext, importer.getLoadedLocations(),importer.getOptionalLocations());
}private ConfigDataEnvironmentContributors processInitial(ConfigDataEnvironmentContributors contributors,ConfigDataImporter importer) {this.logger.trace("Processing initial config data environment contributors without activation context");contributors = contributors.withProcessedImports(importer, null);registerBootstrapBinder(contributors, null, DENY_INACTIVE_BINDING);return contributors;
}