SpringBoot外部化配置相关源码API剖析和扩展

1. 什么是外部化配置？

个人理解是spring提供的属性配置和环境切换功能。核心Api为Environment抽象，而springboot的配置文件(proepreties/yaml)的加载和其密不可分，springboot会从默认的location位置加载数据源并设置到Environment中。根据配置环境来进行属性源的优先级调整

Environment相关类图

Environment类图

2. 加载springboot外部化配置文件在2.4.0和之前版本有较大改动，下面分析会根据不同版本进行不同分析

2.1 springboot2.3以及之前版本

• 在SpringApplication启动的时候在prepareEnvironment阶段会发送ApplicationEnvironmentPreparedEvent事件

• EnvironmentPostProcessorApplicationListener接受到事件会将spring.factories文件中所有的EnvironmentPostProcessor加载并回调其postProcessEnvironment()方法，此时很重要的ConfigFileApplicationListener#postProcessEnvironment()会被回调

  • 添加Random PropertySource

    protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
      //1. 添加Random PropertySource到Environment中
        RandomValuePropertySource.addToEnvironment(environment);
      //2. 创建Loader内置类，传入Environment执行load方法
        new Loader(environment, resourceLoader).load();
    }
  

  • 创建Load对象

        Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {
             //1. 传入外部化配置环境对象
        this.environment = environment;
        //2. 实例化占位符解析器
            this.placeholdersResolver = new PropertySourcesPlaceholdersResolver(this.environment);
        //3. 创建资源加载对象
            this.resourceLoader = (resourceLoader != null) ? resourceLoader : new DefaultResourceLoader(null);
        //4. 以及最重要的加载spring.factories文件中所有的PropertySourceLoader(内置两种:properteies/yaml)
            this.propertySourceLoaders = SpringFactoriesLoader.loadFactories(PropertySourceLoader.class,
                    getClass().getClassLoader());
        }
  

  • 正式进行load外部化配置资源

            void load() {
          //调用静态方法进行加载
          //1. 环境对象
          //2. defaultProperties PropertySource 加载的profiles位置 spring.profiles.active / include
          //3. 处理加载逻辑
                FilteredPropertySource.apply(this.environment, DefaultPropertiesPropertySource.NAME, LOAD_FILTERED_PROPERTY,
                        this::loadWithFilteredProperties);
            }
    

    • 替换如果defaultProperties存在的话，这个属性是SpringApplication构造的时候传入的属性源

        static void apply(ConfigurableEnvironment environment, String propertySourceName, Set<String> filteredProperties,
                Consumer<PropertySource<?>> operation) {
            MutablePropertySources propertySources = environment.getPropertySources();
            PropertySource<?> original = propertySources.get(propertySourceName);
          //1. 查看defaultProperties是否存在
            if (original == null) {
                operation.accept(null);
                return;
            }
          //构造成FilteredPropertySource，然后加载并替换
            propertySources.replace(propertySourceName, new FilteredPropertySource(original, filteredProperties));
            try {
                operation.accept(original);
            }
            finally {
                propertySources.replace(propertySourceName, original);
            }
        }
      

    • loadWithFilteredProperties（PropertySource<?> defaultProperties）加载

    private void loadWithFilteredProperties(PropertySource<?> defaultProperties) {
                this.profiles = new LinkedList<>();
                this.processedProfiles = new LinkedList<>();
                this.activatedProfiles = false;
                this.loaded = new LinkedHashMap<>();
                initializeProfiles(); //1. 初始化profiles相关参数
                while (!this.profiles.isEmpty()) { //2. 将获取到的profile参数依次出栈，进行加载
                    Profile profile = this.profiles.poll();
                    if (isDefaultProfile(profile)) { //3. 这里判断是否是默认的profile，其实这里方法名有奇异，其实应该是不是默认的profile会被添加到Envrionment中
                        addProfileToEnvironment(profile.getName());
                    }
            //4. 加载符合当前profile的配置文件，并添加到Environment最后面
                    load(profile, this::getPositiveProfileFilter, addToLoaded(MutablePropertySources::addLast, false));
                    this.processedProfiles.add(profile);
                }
                //5. 加载 spring.config.name.fileExtension中剩余未加载的(翻阅多种情况，发现只可能在执行该方法的时候外部修改了envrionment的activeProfiles方法才可能进入)
                load(null, this::getNegativeProfileFilter, addToLoaded(MutablePropertySources::addFirst, true));
         //6. 将load到的PropertySource应用到Environment对象中
                addLoadedPropertySources();
         //7. 应用profile到Environment中
            applyActiveProfiles(defaultProperties);
            }
    

    • 这里面核心只需要观察load(profile, this::getPositiveProfileFilter,addToLoaded(MutablePropertySources::addLast, false));

    
     private void load(Profile profile, DocumentFilterFactory filterFactory, DocumentConsumer consumer) {
                //1. 依次获取 spring.cofnig.addtional-location / location / default localtioni 的路径进行迭代
                getSearchLocations().forEach((location) -> {
            //2. 封装成ConfigDataLocation
                    String nonOptionalLocation = ConfigDataLocation.of(location).getValue(); 
                    boolean isDirectory = location.endsWith("/");
            //3. 如果是目录则获取spring.config.name作为文件名称进行加载，不是则传递null
                    Set<String> names = isDirectory ? getSearchNames() : NO_SEARCH_NAMES; 
            //4. load资源
                    names.forEach((name) -> load(nonOptionalLocation, name, profile, filterFactory, consumer));
                });
            }
    
    // --------------
    
            private void load(String location, String name, Profile profile, DocumentFilterFactory filterFactory,
                              DocumentConsumer consumer) {
            //....省略部分非核心方法
                Set<String> processed = new HashSet<>();
          //1. 会迭代我们从spring.factories中获取到的PropertySourceLoader(porperties/yaml)
                for (PropertySourceLoader loader : this.propertySourceLoaders) {
                    for (String fileExtension : loader.getFileExtensions()) {
                        if (processed.add(fileExtension)) {
                //2. 进行加载，并传入profile，拼接的路径名称..
                            loadForFileExtension(loader, location + name, "." + fileExtension, profile, filterFactory,
                                    consumer);
                        }
                    }
                }
            }
    // --------------
    
            //加载核心流程 profile ->  null -> (若没有profile)default -> include -> active
            private void loadForFileExtension(PropertySourceLoader loader, String prefix, String fileExtension,
                                              Profile profile, DocumentFilterFactory filterFactory, DocumentConsumer consumer) {
                DocumentFilter defaultFilter = filterFactory.getDocumentFilter(null); // positive: if document.profiles.isEmpty() return true
                DocumentFilter profileFilter = filterFactory.getDocumentFilter(profile); // positive: if document.profiles contains profile return true | profile = true and document.profiles.isEmptry()
                if (profile != null) {
                    // Try profile-specific file & profile section in profile file (gh-340)
                    String profileSpecificFile = prefix + "-" + profile + fileExtension;
    //1. 优先加载 spring.config.name-{profile}.fileExtension 并通过defaultFilter过滤的(没有spring.profiles的)
                    load(loader, profileSpecificFile, profile, defaultFilter, consumer); 
    //2. 然后加载 匹配spring.profiles和当前 profile匹配的特有属性
                    load(loader, profileSpecificFile, profile, profileFilter, consumer); 
                    // Try profile specific sections in files we've already processed
                    for (Profile processedProfile : this.processedProfiles) {
                        if (processedProfile != null) {
                            String previouslyLoaded = prefix + "-" + processedProfile + fileExtension;
                //3. 加载之前加载过的profile中包含 spring.profiles的特有属性
                            load(loader, previouslyLoaded, profile, profileFilter, consumer); 
                        }
                    }
                }
                // Also try the profile-specific section (if any) of the normal file
           //4. 最后加载spring.config.name.fileExtension 中spring.profiles不为空的
                load(loader, prefix + fileExtension, profile, profileFilter, consumer);
            }
    

    这步进行完毕之后会将所有的外部配置问价加载到org.springframework.boot.context.config.ConfigFileApplicationListener.Loader#loaded属性中

            private Map<Profile, MutablePropertySources> loaded; //保存所有已经加载的PropertySource
    

    • 最后应用propertySource和Profile就大功告成了

    //1. 应用PropertySource
    private void addLoadedPropertySources() {
                MutablePropertySources destination = this.environment.getPropertySources();
                List<MutablePropertySources> loaded = new ArrayList<>(this.loaded.values());
                Collections.reverse(loaded);
                String lastAdded = null;
                Set<String> added = new HashSet<>();
                for (MutablePropertySources sources : loaded) {
                    for (PropertySource<?> source : sources) {
                        if (added.add(source.getName())) {
                //依次添加到Environment中
                            addLoadedPropertySource(destination, lastAdded, source);
                            lastAdded = source.getName();
                        }
                    }
                }
            }
    //2. 应用profile
            private void applyActiveProfiles(PropertySource<?> defaultProperties) {
                List<String> activeProfiles = new ArrayList<>();
                if (defaultProperties != null) {
                    Binder binder = new Binder(ConfigurationPropertySources.from(defaultProperties),
                            new PropertySourcesPlaceholdersResolver(this.environment));
                    activeProfiles.addAll(getDefaultProfiles(binder, "spring.profiles.include"));
                    if (!this.activatedProfiles) {
                        activeProfiles.addAll(getDefaultProfiles(binder, "spring.profiles.active"));
                    }
                }
                this.processedProfiles.stream().filter(this::isDefaultProfile).map(Profile::getName)
                        .forEach(activeProfiles::add);
                this.environment.setActiveProfiles(activeProfiles.toArray(new String[0]));
            }
    

• 最后上一下自己的实验配置属性图，和最后加载的Environment对象结果

实验结果图

//classpath:/applicaiton.properties
name=default
spring.profiles.active=dev,prod
spring.profiles.include=config,test

#---
spring.profiles=test
name=default#test
#---
spring.profiles=negative
name=default#negative

Environment#propertySource

PropertySource结果图

2.2 springboot 2.4版本配置加载

这个版本springboot重构了之前的外部化文件加载方式，并且添加了对各大元计算平台的支持，如Kubernetes的ConfigMap等. 重构了之前使用PropertySourceLoader进行外部化配置地址 -> propertySource的转变，其中核心Api类图如下

SpringBoot2.4核心类图

核心步骤

• 通过SpringApplication的启动生命周期回调到ConfigDataEnvironmentPostProcessor的回调
• 从spring.factories中获取ConfigDataLoader,ConfigDataLocationResolver 加载解析核心组件，并构造成ConfigDataEnvironment对象
• 通过ConfigDataEnvironment#processAndApply()开始加载配置文件逻辑
• 核心加载架构个人总结为三大步和三个阶段
  • 三大步
    • 通过ConfigDataLocationResolver将相关spring.config.import,spring.config.addtional-location,spring.config.location等资源定位路径下的spring.config.name-{profile}.fileExtension资源解析成ConfigDataResource
    • 通过ConfigDataLoader将ConfigDataLocationResolver解析好的资源进行加载，将ConfigDataResource -> ConfigData ， 其中ConfigData是一组ProeprtySource
    • 将加载好的ConfigData添加到Environment中
  • 三大阶段，核心对象为ConfigDataEnvironmentContributors，其中分了三个大阶段对外部化资源进行加载
    • 无profile无CloudPlatform阶段 ， 这个阶段会使用三大步中前两步构造出ConfigData
    • 根据环境参数spring.main.cloud-platform或者环境变量参数来自动探测云计算厂商环境，从而进行二阶段加载
    • 设置profiles,使用Binder Api从绑定的ConfigurationPropertySource中获取spring.profiles / spring.config等资源，进行第三阶段的加载

详细步骤如下

• ConfigDataEnvironmentPostProcessor回调

void postProcessEnvironment(ConfigurableEnvironment environment, ResourceLoader resourceLoader,
      Collection<String> additionalProfiles) {
   try {
      this.logger.trace("Post-processing environment to add config data");
      resourceLoader = (resourceLoader != null) ? resourceLoader : new DefaultResourceLoader();
      //执行ConfigData加载和应用
      getConfigDataEnvironment(environment, resourceLoader, additionalProfiles).processAndApply();
   }
   catch (UseLegacyConfigProcessingException ex) {
      this.logger.debug(LogMessage.format("Switching to legacy config file processing [%s]",
            ex.getConfigurationProperty()));
        //这里兼容了springboot2.4之前版本的实现,可以通过spring.config.use-legacy-processing=true来调整为之前的实现
      //若抛出UseLegacyConfigProcessingException异常则使用老的方式(ConfigFileApplicationListener)进行外部化文件配置加载
      postProcessUsingLegacyApplicationListener(environment, resourceLoader);
   }
}

• ConfigDataEnvironment对象的构造

ConfigDataEnvironment(DeferredLogFactory logFactory, ConfigurableBootstrapContext bootstrapContext,
      ConfigurableEnvironment environment, ResourceLoader resourceLoader, Collection<String> additionalProfiles) {
   Binder binder = Binder.get(environment); //1. 绑定当前Environment对象
   UseLegacyConfigProcessingException.throwIfRequested(binder);
   this.logFactory = logFactory;
   this.logger = logFactory.getLog(getClass());
   //2. 从属性spring.config.on-not-found中获取文件找不到的执行逻辑
   this.notFoundAction = binder.bind(ON_NOT_FOUND_PROPERTY, ConfigDataNotFoundAction.class)
         .orElse(ConfigDataNotFoundAction.FAIL);
   this.bootstrapContext = bootstrapContext;
   this.environment = environment;
   //3. 从spring.factories中获取ConfigDataLocationResolver实现。(可以自己实现，扩展点之一)
   //4. 同时这里面会传入boostrapper/resourceLoader/Binder等参数用于构造参数反射
   this.resolvers = createConfigDataLocationResolvers(logFactory, bootstrapContext, binder, resourceLoader);
   this.additionalProfiles = additionalProfiles;
   //5. 从spring.factories中获取所有的ConfigDataLoader并用反射进行实例化
   this.loaders = new ConfigDataLoaders(logFactory, bootstrapContext);
   //6. 创建ConfigDataEnvironmentContributors对象，里面会根据spring.config.import / location等默认定位参数初始化Contributor
   this.contributors = createContributors(binder);
}

• 解析并加载 processAndApply(),整个外部化配置解析的核心框架，这里能明显看到我上面说明的三大阶段

void processAndApply() {
   //1. 封装ConfigDataImporter对象，里面有解析ConfigDataLocation -> ConfigDataResource 和load ConfigDataResource -> ConfigData之类的操作
   ConfigDataImporter importer = new ConfigDataImporter(this.logFactory, this.notFoundAction, this.resolvers,
         this.loaders);
   this.bootstrapContext.register(Binder.class, InstanceSupplier
         .from(() -> this.contributors.getBinder(null, BinderOption.FAIL_ON_BIND_TO_INACTIVE_SOURCE)));
   //1. 加载和解析ConfigDataLocation -> ConfigDataResource -> ConfigData ,此时还没有导入到Environment中，执行完毕之后应该都是BOUND_IMPORT,且此时绑定了spring.config / spring.profiles相关的配置属性信息
   ConfigDataEnvironmentContributors contributors = processInitial(this.contributors, importer);
   //2. 获取包含Root Contributor中 所有ConfigurationPropertySource的Binder
   Binder initialBinder = contributors.getBinder(null, BinderOption.FAIL_ON_BIND_TO_INACTIVE_SOURCE);
   //3. 重新注册Binder到Bootstrapper中
   this.bootstrapContext.register(Binder.class, InstanceSupplier.of(initialBinder));
   ConfigDataActivationContext activationContext = createActivationContext(initialBinder); //构建激活的上下文对象，此时对元计算平台进行设置
   //4. 带云计算平台参数上下文进行二次迭代
   contributors = processWithoutProfiles(contributors, importer, activationContext);
   //5. 构建profile
   activationContext = withProfiles(contributors, activationContext);
   //6. 带profile参数进行第三次迭代
   contributors = processWithProfiles(contributors, importer, activationContext);
   //7. 应用到Environment对象中
   applyToEnvironment(contributors, activationContext);
}

内容比较复杂，核心为ConfigDataEnvironmrntContributor的几个阶段的处理，可以看其中的内部类Kind

enum Kind {
    //包含了所有的Contributors
   ROOT,
    //上面我们刚创建就属于这个状态
   INITIAL_IMPORT,
    //已经将内部PropertySource应用到Environment中的Contributors
   EXISTING,
    //刚解析构造好ConfigData,还没有绑定spring.config / spring.profiles等环境参数
   UNBOUND_IMPORT,
        //已经绑定好环境参数阶段
   BOUND_IMPORT;
}

接下来继续跟processAndApply()方法

• processInitial : 处理 Kind为INITIAL_IMPORT类型的Contributros ，这里面也是主要的解析配置的地方

    ConfigDataEnvironmentContributors withProcessedImports(ConfigDataImporter importer,
            ConfigDataActivationContext activationContext) {
        //1. 获取Import阶段，分导入前导入后
        ImportPhase importPhase = ImportPhase.get(activationContext);
        this.logger.trace(LogMessage.format("Processing imports for phase %s. %s", importPhase,
                (activationContext != null) ? activationContext : "no activation context"));
        ConfigDataEnvironmentContributors result = this;
        int processed = 0;
        while (true) {
            //1阶段. 初始化为null
            //2阶段. 设置好ActivationContext(相关云计算平台参数进行第二轮的迭代),进行相关云平台过滤
            //3阶段. 进行profile文件的解析和加载
            ConfigDataEnvironmentContributor contributor = getNextToProcess(result, activationContext, importPhase);
            if (contributor == null) {
                this.logger.trace(LogMessage.format("Processed imports for of %d contributors", processed));
                return result;
            }
            if (contributor.getKind() == Kind.UNBOUND_IMPORT) {
                //从UNBOUND_IMPORT Contributor中获取配置属性源
                Iterable<ConfigurationPropertySource> sources = Collections
                        .singleton(contributor.getConfigurationPropertySource());
                // 进行占位符解析
                PlaceholdersResolver placeholdersResolver = new ConfigDataEnvironmentContributorPlaceholdersResolver(
                        result, activationContext, true);
                Binder binder = new Binder(sources, placeholdersResolver, null, null, null);
                ConfigDataEnvironmentContributor bound = contributor.withBoundProperties(binder);
                // 绑定ConfigDataProperties 并进行替换
                result = new ConfigDataEnvironmentContributors(this.logger, this.bootstrapContext,
                        result.getRoot().withReplacement(contributor, bound));
                continue;
            }
            //2.封装Resolver,Loader等相关操作上下文对象
            ConfigDataLocationResolverContext locationResolverContext = new ContributorConfigDataLocationResolverContext(
                    result, contributor, activationContext);
            ConfigDataLoaderContext loaderContext = new ContributorDataLoaderContext(this);
            //3. 从ConfigDataLocationContributor(ConfigDataProperties)中获取ConfigDataLocation(资源路径对象)
            List<ConfigDataLocation> imports = contributor.getImports();
            this.logger.trace(LogMessage.format("Processing imports %s", imports));
            //4. 解析到Map<ConfigDataResource, ConfigData>
            Map<ConfigDataResource, ConfigData> imported = importer.resolveAndLoad(activationContext,
                    locationResolverContext, loaderContext, imports);
            this.logger.trace(LogMessage.of(() -> imported.isEmpty() ? "Nothing imported" : "Imported "
                    + imported.size() + " resource " + ((imported.size() != 1) ? "s" : "") + imported.keySet()));
            ConfigDataEnvironmentContributor contributorAndChildren = contributor.withChildren(importPhase,
                    asContributors(imported));
            result = new ConfigDataEnvironmentContributors(this.logger, this.bootstrapContext, //返回设置好Child Contributor的结果集，然后继续下一次迭代
                    result.getRoot().withReplacement(contributor, contributorAndChildren));
            processed++;
        }
    }

• getNextToProcess() ： 用来获取ConfigDataEnvironmentContributes中下次个满足解析的Contributor

    private ConfigDataEnvironmentContributor getNextToProcess(ConfigDataEnvironmentContributors contributors,
            ConfigDataActivationContext activationContext, ImportPhase importPhase) {
        for (ConfigDataEnvironmentContributor contributor : contributors.getRoot()) {
            /**
             * 1. 刚进来是INITIAL_IMPORT
             * 2. activationContext = null
             * 3. importPhase = BEFORE_PROFILE_ACTIVATION
             */
            if (contributor.getKind() == Kind.UNBOUND_IMPORT
                    || isActiveWithUnprocessedImports(activationContext, importPhase, contributor)) {
                return contributor;
            }
        }
        return null;
    }
  
    private boolean isActiveWithUnprocessedImports(ConfigDataActivationContext activationContext,
            ImportPhase importPhase, ConfigDataEnvironmentContributor contributor) {
        //ConfigDataProperties -> ConfigDataActivationContext (前两者为null为true) ( onCloudPlatform -> Profiles) (为null为true/匹配当前环境)
        return contributor.isActive(activationContext) && contributor.hasUnprocessedImports(importPhase);
    }
  //下面是一些列的判断方法,依次递进。返回true表示当前为激活环境，现在阶段Kind为INITIAL_IMPORT，且activation为null
  //所以会返回true
    boolean isActive(ConfigDataActivationContext activationContext) {
        return this.properties == null || this.properties.isActive(activationContext);
    }
    boolean isActive(ConfigDataActivationContext activationContext) {
        return this.activate == null || this.activate.isActive(activationContext);
    }
  boolean isActive(ConfigDataActivationContext activationContext) {
    if (activationContext == null) {
      return false;
    }
    boolean activate = true;
    activate = activate && isActive(activationContext.getCloudPlatform());
    activate = activate && isActive(activationContext.getProfiles());
    return activate;
  }
  

  • 构造ConfigDataLocationResolver，ConfigDataLoader等上下文对象

            //2.封装Resolver,Loader等相关操作上下文对象
            ConfigDataLocationResolverContext locationResolverContext = new ContributorConfigDataLocationResolverContext(
                    result, contributor, activationContext);
            ConfigDataLoaderContext loaderContext = new ContributorDataLoaderContext(this);
  

  • 获取默认的定位资源并进行解析加载

  //3. 从ConfigDataLocationContributor(ConfigDataProperties)中获取ConfigDataLocation(资源路径对象)
  List<ConfigDataLocation> imports = contributor.getImports();
  this.logger.trace(LogMessage.format("Processing imports %s", imports));
  //4. 解析到Map<ConfigDataResource, ConfigData>
  Map<ConfigDataResource, ConfigData> imported = importer.resolveAndLoad(activationContext,
        locationResolverContext, loaderContext, imports);
  

  • resolveAndLoad ： 解析configDataLocation为ConfigDataResource,随后ConfingDataLoader#load为ConfigData，并返回Map<ConfigDataResource, ConfigData>映射关系，具体解析流程，我直接截取了最核心的解析和加载代码，如下

    Map<ConfigDataResource, ConfigData> resolveAndLoad(ConfigDataActivationContext activationContext,
            ConfigDataLocationResolverContext locationResolverContext, ConfigDataLoaderContext loaderContext,
            List<ConfigDataLocation> locations) {
        try {
            //1. 初始化import阶段profile为空 , 这个第三阶段会派上用场
            Profiles profiles = (activationContext != null) ? activationContext.getProfiles() : null;
            //2. 使用ConfigDateLocationResolver进行加载和解析
        // ConfigDataResolutionResult 包含了ConfigDataLocation 和ConfigDataResource(解析结果)
            List<ConfigDataResolutionResult> resolved = resolve(locationResolverContext, profiles, locations);
            //3. 使用ConfigDataLoader将ConfigDataResource -> ConfigData -> （PropertySource）
            return load(loaderContext, resolved);
        }
        catch (IOException ex) {
            throw new IllegalStateException("IO error on loading imports from " + locations, ex);
        }
    }
  
  // resolver() 核心 ,根这上面resolve方法一直跟就找到了,ConfigDataLocationResolvers#resolve()
    private List<ConfigDataResolutionResult> resolve(ConfigDataLocationResolver<?> resolver,
            ConfigDataLocationResolverContext context, ConfigDataLocation location, Profiles profiles) {
       //进行解析
        List<ConfigDataResolutionResult> resolved = resolve(location, () -> resolver.resolve(context, location));
        if (profiles == null) {
            return resolved;
        }
        //下面是第三阶段用来进行profile环境加载
        List<ConfigDataResolutionResult> profileSpecific = resolve(location,
                () -> resolver.resolveProfileSpecific(context, location, profiles));
        return merge(resolved, profileSpecific);
    }
  
  //ConfigDataImport#load() , 核心使用刚才加载到的ConfigDataResource列表进行ConfigDataLoader#load加载
  //我们可以通过在META-INF/spring.factories中配置我们自己实现的ConfigDataLoader进行扩展加载其他格式的外部化环境，
  // 比如最后我会演示扩展实现一个加载json文件的Loader
    private Map<ConfigDataResource, ConfigData> load(ConfigDataLoaderContext loaderContext,
            List<ConfigDataResolutionResult> candidates) throws IOException {
        Map<ConfigDataResource, ConfigData> result = new LinkedHashMap<>();
        //1. 从后向前迭代ConfigDataResolutionResult(包含ConfigDataLocation,ConfigDataResource)
      //2. 这里有个细节，为什么是从后往前遍历？因为之前解析profile的时候是从优先级低 -> 高
        for (int i = candidates.size() - 1; i >= 0; i--) {
            ConfigDataResolutionResult candidate = candidates.get(i);
            ConfigDataLocation location = candidate.getLocation();
            ConfigDataResource resource = candidate.getResource();
            if (this.loaded.add(resource)) { //set缓存并去重
                try {
                    //2. ConfigDataLoader加载将ConfigDataResource -> ConfigData （PropetySource）又是一个扩展点
                    ConfigData loaded = this.loaders.load(loaderContext, resource);
                    if (loaded != null) {
                        result.put(resource, loaded);
                    }
                }
                catch (ConfigDataNotFoundException ex) {
                    handle(ex, location);
                }
            }
        }
        return Collections.unmodifiableMap(result);
    }
  

  这边核心的三步我们就完成了两步，解析和加载，随后就是一些重复逻辑，加载另外两阶段的配置，这边挑一些细节来展示,我们回到ConfigDataEnvironment#processAndApply()，刚刚执行完processInitia()方法逻辑，解析和加载了第一阶段，随便进行云计算厂商的配置整合，核心在createActivationContext（）

    void processAndApply() {
        //1. 封装ConfigDataImporter对象，里面有解析ConfigDataLocation -> ConfigDataResource 和load ConfigDataResource -> ConfigData之类的操作
        ConfigDataImporter importer = new ConfigDataImporter(this.logFactory, this.notFoundAction, this.resolvers,
                this.loaders);
        this.bootstrapContext.register(Binder.class, InstanceSupplier
                .from(() -> this.contributors.getBinder(null, BinderOption.FAIL_ON_BIND_TO_INACTIVE_SOURCE)));
        //1. 加载和解析ConfigDataLocation -> ConfigDataResource -> ConfigData ,此时还没有导入到Environment中，执行完毕之后应该都是BOUND_IMPORT,且此时绑定了spring.config / spring.profiles相关的配置属性信息
        ConfigDataEnvironmentContributors contributors = processInitial(this.contributors, importer);
        //2. 获取包含Root Contributor中 所有ConfigurationPropertySource的Binder
        Binder initialBinder = contributors.getBinder(null, BinderOption.FAIL_ON_BIND_TO_INACTIVE_SOURCE);
        //3. 重新注册Binder到Bootstrapper中
        this.bootstrapContext.register(Binder.class, InstanceSupplier.of(initialBinder));
        ConfigDataActivationContext activationContext = createActivationContext(initialBinder); //构建激活的上下文对象，此时对元计算平台进行设置
        //4. 带云计算平台参数上下文进行二次迭代
        contributors = processWithoutProfiles(contributors, importer, activationContext);
        //5. 构建profile
        activationContext = withProfiles(contributors, activationContext);
        //6. 带profile参数进行第三次迭代
        contributors = processWithProfiles(contributors, importer, activationContext);
        //7. 应用到Environment对象中
        applyToEnvironment(contributors, activationContext);
    }
  

  • 自动探测和整合第三场云厂商 ，如k8s等.详细可以参考CloudPlatform这个类，里面有自动探测和通过配置相关环境变量的方法来进行设置

    private CloudPlatform deduceCloudPlatform(Environment environment, Binder binder) {
        for (CloudPlatform candidate : CloudPlatform.values()) {
  //尝试从Environment上下文中获取spring.main.cloud-platform,若有指定对应的云计算厂商则直接返回对应的CloudPlatform
            if (candidate.isEnforced(binder)) { 
                return candidate;
            }
        }
  //从环境变量中寻找是否有对应云平台的环境变量参数,比如k8s(svc相关环境参数): KUBERNETES_SERVICE_HOST/KUBERNETES_SERVICE_PORT
        return CloudPlatform.getActive(environment);
    }
  

  • 获取Environment中的profile属性

    private ConfigDataActivationContext withProfiles(ConfigDataEnvironmentContributors contributors,
            ConfigDataActivationContext activationContext) {
        this.logger.trace("Deducing profiles from current config data environment contributors");
        Binder binder = contributors.getBinder(activationContext, BinderOption.FAIL_ON_BIND_TO_INACTIVE_SOURCE);
        try {
            //优先设置构造SpringApplication的addtionalProfile
            Set<String> additionalProfiles = new LinkedHashSet<>(this.additionalProfiles);
        //设置include profile
            additionalProfiles.addAll(getIncludedProfiles(contributors, activationContext));
        //设置active profile 、 default profile
            Profiles profiles = new Profiles(this.environment, binder, additionalProfiles);
            return activationContext.withProfiles(profiles);
        }
        catch (BindException ex) {
            if (ex.getCause() instanceof InactiveConfigDataAccessException) {
                throw (InactiveConfigDataAccessException) ex.getCause();
            }
            throw ex;
        }
    }
  

  • 随后完成第三阶段的解析和加载以及最后应用到Environment中

        //6. 带profile参数进行第三次迭代
        contributors = processWithProfiles(contributors, importer, activationContext);
        //7. 应用到Environment对象中
        applyToEnvironment(contributors, activationContext);
  

  2.3 两种版本不同的加载优先级如下

  
  //springboot2.4之前
  //location优先级为: spring.config.addtional-location > spring.config.location or default
  //这里的default指springboot默认加载位置 classpath:/ classpath:/config/ ...
  //profile优先级：
  //spring.profiles.active > spring.profiles.include
  //且这里如果有spring.profiles指定的多环境格式,如下，此时加载test环境的时候，spring.profiles=test也会随后加载
  
  name=default
  spring.profiles.active=dev,prod
  spring.profiles.include=config,test
  #---
  spring.profiles=test
  name=default#test
  
  //springboot2.4之后
  //location优先级为: spring.config.import > addtionial-location > location
  //profile优先级
  //spring.profiles.include > active(之间还多了一个spring.config.group)
  

  总结：

  springboot2.4和之前版本实现有较大差距，前者扩展了通过spring.config.import导入资源，并且资源加载来源更加宽广了，springboot内建的实现甚至可以从svn中加载配置。而下面也将进行简单的两个版扩展配置的方式

  spring boot 2.4之前, 只需要实现PropertySourceLoader接口然后添加到META-INF/spring.factories即可

  • 自定义CustomPropertySourceLoader

  //自定义json后缀资源加载器
  public class CustomPropertySourceLoader implements PropertySourceLoader {
  
      public static final String CUSTOM_PREFIX = "json";
  
      @Override
      public String[] getFileExtensions() {
          return new String[]{CUSTOM_PREFIX};
      }
  
      @Override
      public List<PropertySource<?>> load(String name, Resource resource) throws IOException {
          Map<String, Object> result  =  new ObjectMapper().readValue(resource.getURL(),new TypeReference<Map<String,Object>>(){});
          return Collections.singletonList(new MapPropertySource("JSON_PROPERTY_SOURCE", result));
      }
  }
  

  • 配置文件

  #自定义ConfigDataLocationResolver -> ConfigDataLocation -> ConfigDataResource
  org.springframework.boot.context.config.ConfigDataLocationResolver=\
  boot.in.action.bootsourcelearning.configdata.CustomConfigDataLocationResolver
  

  spring boot2.4扩展

  • 实现ConfigDataLocationResolver ， 和ConfigDataResource , 这种自定义实现将可以解析custom:前缀的资源，实现参考了ConfigTreeDataLocationResolver

  public class CustomConfigDataLocationResolver implements ConfigDataLocationResolver<CustomConfigDataResource> {
  
      public static final String CUSTOM_CONFIG_PREFIX = "custom:";
  
      @Override
      public boolean isResolvable(ConfigDataLocationResolverContext context, ConfigDataLocation location) {
          return location.hasPrefix(CUSTOM_CONFIG_PREFIX) && location.getValue().endsWith(".properties");
      }
  
      @Override
      public List<CustomConfigDataResource> resolve(ConfigDataLocationResolverContext context, ConfigDataLocation location) {
          List<CustomConfigDataResource> result = new ArrayList<>();
          try {
              Resource[] resources = new PathMatchingResourcePatternResolver().getResources(location.getValue().substring(CUSTOM_CONFIG_PREFIX.length()));
              for (Resource resource : resources) {
                  result.add(new CustomConfigDataResource(PropertiesLoaderUtils.loadProperties(resource)));
              }
          } catch (IOException e) {
              if (location.isOptional()) {
                  log.warn("not found resource :{}", location.getValue());
              } else {
                  ReflectionUtils.rethrowRuntimeException(e);
              }
          }
          return result;
      }
  }
  

  • 实现ConfigDataLoader

  public class CustomConfigDataLoader implements ConfigDataLoader<CustomConfigDataResource> {
  
      @Override
      public ConfigData load(ConfigDataLoaderContext context, CustomConfigDataResource resource) throws ConfigDataResourceNotFoundException {
          Properties properties = resource.getProperties();
          return new ConfigData(Collections.singleton(new PropertiesPropertySource("FILE_PROPERTY_SOURCE", properties)));
      }
  }
  

  • 配置文件

  
  #自定义ConfigDataLocation ConfigDataResource->ConfigData
  org.springframework.boot.context.config.ConfigDataLoader=\
  boot.in.action.bootsourcelearning.configdata.CustomConfigDataLoader
  
  org.springframework.boot.env.PropertySourceLoader=\
  boot.in.action.bootsourcelearning.configdata.CustomPropertySourceLoader
  

  • 测试输入程序如下

      public static void main(String[] args) {
          ConfigurableApplicationContext context = new SpringApplicationBuilder(BootSourceLearningApplication.class)
  //                .properties("spring.config.use-legacy-processing=true")
                  .properties("spring.config.additional-location=classpath:/custom/")
                  .properties("spring.config.import=classpath:/custom/custom.json,optional:custom:/custom/custom.properties")
                  .applicationStartup(new BufferingApplicationStartup(2048))
                  .web(WebApplicationType.SERVLET)
                  .run(args);
          context.getEnvironment().getPropertySources().forEach(System.out::println);
      }
  
  //输出结果如下,成功加载custom前缀和 .json后缀的PropertySource
  MapPropertySource {name='server.ports'}
  ConfigurationPropertySourcesPropertySource {name='configurationProperties'}
  StubPropertySource {name='servletConfigInitParams'}
  ServletContextPropertySource {name='servletContextInitParams'}
  PropertiesPropertySource {name='systemProperties'}
  OriginAwareSystemEnvironmentPropertySource {name='systemEnvironment'}
  RandomValuePropertySource {name='random'}
  PropertiesPropertySource {name='FILE_PROPERTY_SOURCE'} //custom前缀
  MapPropertySource {name='JSON_PROPERTY_SOURCE'} //.json后缀