SpringBoot Environment使用

在上一篇中，我们的类加载器使用environment获取一些属性，如下图

 

 下面我们介绍下environment的使用

1、进入启动方法run，定位到prepareEnvironment方法

 

 

 

2、进到prepareEnvironment方法

 

 

 

3、进入getOrCreateEnvironment方法。实例化了StandardServletEnvironment

 

 

 

进入父类AbstractEnvironment的构造函数

 

 

 

1)、进入customizePropertySources方法。

增加servletConfigInitParams属性源和servletContextInitParams属性源，添加jndi属性源

然后调用父类的super.customizePropertySources(propertySources);

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protected void customizePropertySources(MutablePropertySources propertySources) {     propertySources.addLast(new StubPropertySource("servletConfigInitParams"));     propertySources.addLast(new StubPropertySource("servletContextInitParams"));     if(JndiLocatorDelegate.isDefaultJndiEnvironmentAvailable()) {         propertySources.addLast(new JndiPropertySource("jndiProperties"));     }       super.customizePropertySources(propertySources); }

　　

2)、进入customizePropertySources，增加两个属性源（系统属性源和系统环境属性源）

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protected void customizePropertySources(MutablePropertySources propertySources) {     propertySources.addLast(             new PropertiesPropertySource(SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME, getSystemProperties()));     propertySources.addLast(             new SystemEnvironmentPropertySource(SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, getSystemEnvironment())); }

　里面getSystemProperties方法，主要有Java的版本号，Java虚拟机名称等

 

 

 

4、然后回到configureEnvironment方法

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protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) {     if (this.addConversionService) {         ConversionService conversionService = ApplicationConversionService.getSharedInstance();         environment.setConversionService((ConfigurableConversionService) conversionService);     }     configurePropertySources(environment, args);     configureProfiles(environment, args); }

　　

1） 进入configurePropertySources(environment, args);

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protected void configurePropertySources(ConfigurableEnvironment environment, String[] args) {     MutablePropertySources sources = environment.getPropertySources();     if (this.defaultProperties != null && !this.defaultProperties.isEmpty()) {         sources.addLast(new MapPropertySource("defaultProperties", this.defaultProperties));     }     if (this.addCommandLineProperties && args.length > 0) {         String name = CommandLinePropertySource.COMMAND_LINE_PROPERTY_SOURCE_NAME;         if (sources.contains(name)) {             PropertySource<?> source = sources.get(name);             CompositePropertySource composite = new CompositePropertySource(name);             composite.addPropertySource(                     new SimpleCommandLinePropertySource("springApplicationCommandLineArgs", args));             composite.addPropertySource(source);             sources.replace(name, composite);         }         else {             sources.addFirst(new SimpleCommandLinePropertySource(args));         }     } }

　　这个方法主要是添加defaultProperties默认属性源（sources.addLast(new MapPropertySource("defaultProperties", this.defaultProperties));

）和命令属性源sources.addFirst(new SimpleCommandLinePropertySource(args));

进入SimpleCommandLinePropertySource的构造函数

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public SimpleCommandLinePropertySource(String... args) {     super(new SimpleCommandLineArgsParser().parse(args)); }

　　里面调用了parse函数。命令的定义是我们前面介绍过的。解析命令的时候，判断是否以“--”开头

 

 

 

2） 进入configureProfiles。profile我们后面在进行介绍  SpringBoot Profile源码介绍

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protected void configureProfiles(ConfigurableEnvironment environment, String[] args) {     environment.getActiveProfiles(); // ensure they are initialized     // But these ones should go first (last wins in a property key clash)     Set<String> profiles = new LinkedHashSet<>(this.additionalProfiles);     profiles.addAll(Arrays.asList(environment.getActiveProfiles()));     environment.setActiveProfiles(StringUtils.toStringArray(profiles)); }

　　

3、 listeners.environmentPrepared(environment)

发布environmentPrepared事件，这里就是监听器的实现。进入environmentPrepared方法

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public void environmentPrepared(ConfigurableEnvironment environment) {     for (SpringApplicationRunListener listener : this.listeners) {         listener.environmentPrepared(environment);     } }

　进入listener.environmentPrepared(environment);里面调用广播器广播一个事件

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@Override public void environmentPrepared(ConfigurableEnvironment environment) {     this.initialMulticaster             .multicastEvent(new ApplicationEnvironmentPreparedEvent(this.application, this.args, environment)); }

　进入广播事件方法。

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public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {     ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));     Executor executor = getTaskExecutor();     for (ApplicationListener<?> listener : getApplicationListeners(event, type)) {         if (executor != null) {             executor.execute(() -> invokeListener(listener, event));         }         else {             invokeListener(listener, event);         }     } }

　　在此方法中，获得对该事件感兴趣的监听器，遍历监听器，调用invokeListener方法。

 

监听器的部分在前面已经介绍过了，这里我们主要看下监听器都做了什么？

进入doInvokeListener方法

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private void doInvokeListener(ApplicationListener listener, ApplicationEvent event) {     try {         listener.onApplicationEvent(event);     }     catch (ClassCastException ex) {         String msg = ex.getMessage();         if (msg == null || matchesClassCastMessage(msg, event.getClass())) {             // Possibly a lambda-defined listener which we could not resolve the generic event type for             // -> let's suppress the exception and just log a debug message.             Log logger = LogFactory.getLog(getClass());             if (logger.isTraceEnabled()) {                 logger.trace("Non-matching event type for listener: " + listener, ex);             }         }         else {             throw ex;         }     } }

　　

然后进入listener.onApplicationEvent(event);方法

 

 

 然后进入onApplicationEnvironmentPreparedEvent方法

 

 

 方法loadPostProcessors是获得属性文件中对该监听器的实现类有哪些。

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List<EnvironmentPostProcessor> loadPostProcessors() {     return SpringFactoriesLoader.loadFactories(EnvironmentPostProcessor.class, getClass().getClassLoader()); }

　该配置文件配置如下：

 

 

 

配置文件由三个EnvironmentPostProcessor，在把当前的添加进去postProcessors.add(this);就有四个了。然后依次遍历这四个EnvironmentPostProcessor

 

 

 

我们进入其中一个EnvironmentPostProcessor，如ConfigFileApplicationListener。里面调用了addPropertySources(environment, application.getResourceLoader());

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

　　然后进入addPropertySources方法

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protected void addPropertySources(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {     RandomValuePropertySource.addToEnvironment(environment);     new Loader(environment, resourceLoader).load(); }

　　RandomValuePropertySource.addToEnvironment(environment);这个方法添加了一个随机的属性源

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public static void addToEnvironment(ConfigurableEnvironment environment) {     environment.getPropertySources().addAfter(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,             new RandomValuePropertySource(RANDOM_PROPERTY_SOURCE_NAME));     logger.trace("RandomValuePropertySource add to Environment"); }

　　然后进入new Loader(environment, resourceLoader).load();的load方法。添加application-profile.(properties|yml)属性集

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public void load() {     this.profiles = new LinkedList<>();     this.processedProfiles = new LinkedList<>();     this.activatedProfiles = false;     this.loaded = new LinkedHashMap<>();     initializeProfiles();     while (!this.profiles.isEmpty()) {         Profile profile = this.profiles.poll();         if (profile != null && !profile.isDefaultProfile()) {             addProfileToEnvironment(profile.getName());         }         load(profile, this::getPositiveProfileFilter, addToLoaded(MutablePropertySources::addLast, false));         this.processedProfiles.add(profile);     }     resetEnvironmentProfiles(this.processedProfiles);     load(null, this::getNegativeProfileFilter, addToLoaded(MutablePropertySources::addFirst, true));     addLoadedPropertySources(); }

　　关于profile留在后面介绍。  SpringBoot Profile源码介绍

 

 

 

4、bindToSpringApplication(environment);

进入bindToSpringApplication方法

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protected void bindToSpringApplication(ConfigurableEnvironment environment) {     try {         Binder.get(environment).bind("spring.main", Bindable.ofInstance(this));     }     catch (Exception ex) {         throw new IllegalStateException("Cannot bind to SpringApplication", ex);     } }

　　

 

5、environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,  deduceEnvironmentClass());

使用判断convertEnvironmentIfNecessary当前环境是否是指定类型，是的话就返回。否的话再new一个环境，把值赋值到新的实例化的环境中

 

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StandardEnvironment convertEnvironmentIfNecessary(ConfigurableEnvironment environment,         Class<? extends StandardEnvironment> type) {     if (type.equals(environment.getClass())) {         return (StandardEnvironment) environment;     }     return convertEnvironment(environment, type); }   private StandardEnvironment convertEnvironment(ConfigurableEnvironment environment,         Class<? extends StandardEnvironment> type) {     StandardEnvironment result = createEnvironment(type);     result.setActiveProfiles(environment.getActiveProfiles());     result.setConversionService(environment.getConversionService());     copyPropertySources(environment, result);     return result; }

　　

 

6、ConfigurationPropertySources.attach(environment); 增加configurationProperties属性源