spring boot 源码探索（三）
4、ApplicationArguments applicationArguments = new DefaultApplicationArguments(args);
listeners.starting()执行完后，接着执行new DefaultApplicationArguments对象。该对象对args参数封装，创建一个PropertySource，来存放args参数。
public DefaultApplicationArguments(String[] args) { Assert.notNull(args, "Args must not be null"); this.source = new Source(args); this.args = args; }
private static class Source extends SimpleCommandLinePropertySource { Source(String[] args) { super(args); } }
Source继承SimpleCommandLinePropertySource、SimpleCommandLinePropertySource最后继承PropertySource抽象类。
4、ConfigurableEnvironment environment = prepareEnvironment(listeners, applicationArguments);
environment 代表程序的运行环境，这里prepareEvironment方法是准备运行环境，listeners 和args 参数传进去。prepareEvironment内容：
private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners, ApplicationArguments applicationArguments) { ConfigurableEnvironment environment = getOrCreateEnvironment(); //创建environment对象 configureEnvironment(environment, applicationArguments.getSourceArgs()); //配置运行环境参数 listeners.environmentPrepared(environment); //广播监听
if (isWebEnvironment(environment) && !this.webEnvironment) { environment = convertToStandardEnvironment(environment); } return environment; }
首先调用getOrCreateEnvironment 创建一个运行环境environment。根据webEnvironment 判定，创建enviroment类型，这里在initialize的时候webEnvironment 已经是true。所以创建了一个standardServletEnvironment 的environment对象。
private ConfigurableEnvironment getOrCreateEnvironment() { if (this.environment != null) { return this.environment; } if (this.webEnvironment) { return new StandardServletEnvironment(); } return new StandardEnvironment(); }
接着进行config Environment 环境，configureEnvironment方法主要做两件事、configurePropertySources 和 configureProfiles 处理，处理propertySource类型和profiles类型的配置处理。
protected void configureEnvironment(ConfigurableEnvironment environment, String[] args) { configurePropertySources(environment, args); configureProfiles(environment, args); }
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( name + "-" + args.hashCode(), args)); composite.addPropertySource(source); sources.replace(name, composite); } else { sources.addFirst(new SimpleCommandLinePropertySource(args)); } } } 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<String>(this.additionalProfiles); profiles.addAll(Arrays.asList(environment.getActiveProfiles())); environment.setActiveProfiles(profiles.toArray(new String[profiles.size()])); }
在configureProertySources中，首先查看defaultProperties是否为空，不为null，则添加该Properties进environment 环境中，然后根据addCommandLineProperties和args参数是否大于0来判断是添加还是替换source。args参数为0，则添加一个由args参数组成的ProertySources，添加到environment 中sources的第一位置（addFirst添加到第一位置，确保main方法中的配置是最优先的，且可以覆盖其他地方的配置）。在本方法中，defaultProperties默认为空，args参数个数未大于0.所以这个方法什么都没有做。
在configureProfiles 中，首先先获key 为spring.profiles.active 的配置项，添加到environment中，然后添加additionalProfiles到配置项profiles中。spring.profiles.active 未配置，additionalProfiles是空对象，所以这个方法实际上也是没有做具体操作。至此，configureEnvironment 方法操作完成，接着调用监听器广播器，发布一个环境准备事件listeners.environmentPrepared(environment)，事件发布跟前面发布的start事件过程是一样的，这里发布了一个ApplicationEnvironmentPreparedEvent事件。
// 发布事件
public void environmentPrepared(ConfigurableEnvironment environment) { this.initialMulticaster.multicastEvent(new ApplicationEnvironmentPreparedEvent( this.application, this.args, environment)); }
下面看看监听器响应事件内容、看看多少个监听器响应了该事件，并做了什么操作：首先ClearCachesApplicationListener和ParentContextCloserApplicationListener未监听。
FileEncodingApplicationListener 监听器监听了该事件，监听代码执行内容为：
public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) { RelaxedPropertyResolver resolver = new RelaxedPropertyResolver( event.getEnvironment(), "spring."); if (resolver.containsProperty("mandatoryFileEncoding")) { String encoding = System.getProperty("file.encoding"); String desired = resolver.getProperty("mandatoryFileEncoding"); if (encoding != null && !desired.equalsIgnoreCase(encoding)) { logger.error("System property 'file.encoding' is currently '" + encoding + "'. It should be '" + desired + "' (as defined in 'spring.mandatoryFileEncoding')."); logger.error("Environment variable LANG is '" + System.getenv("LANG") + "'. You could use a locale setting that matches encoding='" + desired + "'."); logger.error("Environment variable LC_ALL is '" + System.getenv("LC_ALL") + "'. You could use a locale setting that matches encoding='" + desired + "'."); throw new IllegalStateException( "The Java Virtual Machine has not been configured to use the " + "desired default character encoding (" + desired + ")."); } } }
看得出是获取系统的属性mandatoryFileEncoding 和 file.encoding属性，判定是否一致，这里没有配置mandatoryFileEncoding，所有这里的方法，if条件内容就不执行，该监听器没有做任何事情。
AnsiOutputApplicationListener 监听器监听该事件，代码内容：
public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) { RelaxedPropertyResolver resolver = new RelaxedPropertyResolver( event.getEnvironment(), "spring.output.ansi."); if (resolver.containsProperty("enabled")) { String enabled = resolver.getProperty("enabled"); AnsiOutput.setEnabled(Enum.valueOf(Enabled.class, enabled.toUpperCase())); } if (resolver.containsProperty("console-available")) { AnsiOutput.setConsoleAvailable( resolver.getProperty("console-available", Boolean.class)); } }
也是通过属性解析器，获取到spring.output.ansi和console-available属性，然后对AnsiOutput类进行设置。（AnsiOutput类的解释里是 “生成ANSI编码的输出。。。。”，没搞懂）这里没有配置那两个属性，所以这个监听器也是没有做任何操作。
ConfigFileApplicationListener监听器监听了事件。
public void onApplicationEvent(ApplicationEvent event) { if (event instanceof ApplicationEnvironmentPreparedEvent) { onApplicationEnvironmentPreparedEvent( (ApplicationEnvironmentPreparedEvent) event); } if (event instanceof ApplicationPreparedEvent) { onApplicationPreparedEvent(event); } } private void onApplicationEnvironmentPreparedEvent( ApplicationEnvironmentPreparedEvent event) { List<EnvironmentPostProcessor> postProcessors = loadPostProcessors(); postProcessors.add(this); AnnotationAwareOrderComparator.sort(postProcessors); for (EnvironmentPostProcessor postProcessor : postProcessors) { postProcessor.postProcessEnvironment(event.getEnvironment(), event.getSpringApplication()); } } List<EnvironmentPostProcessor> loadPostProcessors() { return SpringFactoriesLoader.loadFactories(EnvironmentPostProcessor.class, getClass().getClassLoader()); }
可以看出，该监听器通过loadFactories加载spring.factories中的两个processor处理器，分别是CloudFoundryVcapEnvironmentPostProcessor和SpringApplicationJsonEnvironmentPostProcessor处理器。然后执行两个处理器的postProcessEnvironment方法，用于处理配置文件配置CloudFoundry和Json相关信息。这里没有做任何相关配置，所以这两个处理器未处理任何事情。
LoggingApplicationListener 监听器监听该事件，用于初始化日志工作、在ApplicationStart事件中，已经做了预初始化，这里做初始化，默认选用的是logback日志
public void onApplicationEvent(ApplicationEvent event) { if (event instanceof ApplicationStartingEvent) { onApplicationStartingEvent((ApplicationStartingEvent) event); } else if (event instanceof ApplicationEnvironmentPreparedEvent) { onApplicationEnvironmentPreparedEvent( (ApplicationEnvironmentPreparedEvent) event); } else if (event instanceof ApplicationPreparedEvent) { onApplicationPreparedEvent((ApplicationPreparedEvent) event); } else if (event instanceof ContextClosedEvent && ((ContextClosedEvent) event) .getApplicationContext().getParent() == null) { onContextClosedEvent(); } else if (event instanceof ApplicationFailedEvent) { onApplicationFailedEvent(); } }
private void onApplicationEnvironmentPreparedEvent( ApplicationEnvironmentPreparedEvent event) { if (this.loggingSystem == null) { this.loggingSystem = LoggingSystem .get(event.getSpringApplication().getClassLoader()); } initialize(event.getEnvironment(), event.getSpringApplication().getClassLoader()); }
protected void initialize(ConfigurableEnvironment environment, ClassLoader classLoader) { new LoggingSystemProperties(environment).apply(); LogFile logFile = LogFile.get(environment); if (logFile != null) { logFile.applyToSystemProperties(); } initializeEarlyLoggingLevel(environment); initializeSystem(environment, this.loggingSystem, logFile); initializeFinalLoggingLevels(environment, this.loggingSystem); registerShutdownHookIfNecessary(environment, this.loggingSystem); }
到这里，监听器都监听并执行监听操作完成了，接着判定一下是否是web environment 环境，不是，就创建标准的StandardEnvironment 环境返回。
if (isWebEnvironment(environment) && !this.webEnvironment) { environment = convertToStandardEnvironment(environment); }
private ConfigurableEnvironment convertToStandardEnvironment( ConfigurableEnvironment environment) { StandardEnvironment result = new StandardEnvironment(); removeAllPropertySources(result.getPropertySources()); result.setActiveProfiles(environment.getActiveProfiles()); for (PropertySource<?> propertySource : environment.getPropertySources()) { if (!SERVLET_ENVIRONMENT_SOURCE_NAMES.contains(propertySource.getName())) { result.getPropertySources().addLast(propertySource); } } return result; }
这样 prepareEnvironment()方法就执行完成了，然后返回ConfigurableEnvironment 对象environment。接着执行Banner 输出。并执行的图标显示。
5、Banner printedBanner = printBanner(environment);
printBanner 方法在应用程序启动时候打印一个图案，并输出一些版本信息。
private Banner printBanner(ConfigurableEnvironment environment) { if (this.bannerMode == Banner.Mode.OFF) { return null; } ResourceLoader resourceLoader = this.resourceLoader != null ? this.resourceLoader : new DefaultResourceLoader(getClassLoader()); SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter( resourceLoader, this.banner); if (this.bannerMode == Mode.LOG) { return bannerPrinter.print(environment, this.mainApplicationClass, logger); } return bannerPrinter.print(environment, this.mainApplicationClass, System.out); }
从代码看首选判定是否开启banner显示，若为off，将返回空值，不打印信息。然后创建一个bannerPrinter 打印对象。调用该对象的print方法打印banner图案信息。如果bannerMode是Log则通过logger打印一句信息，否则则通过system.out 打印
public Banner print(Environment environment, Class<?> sourceClass, Log logger) { Banner banner = getBanner(environment, this.fallbackBanner); try { logger.info(createStringFromBanner(banner, environment, sourceClass)); } catch (UnsupportedEncodingException ex) { logger.warn("Failed to create String for banner", ex); } return new PrintedBanner(banner, sourceClass); }
public Banner print(Environment environment, Class<?> sourceClass, PrintStream out) { Banner banner = getBanner(environment, this.fallbackBanner); banner.printBanner(environment, sourceClass, out); return new PrintedBanner(banner, sourceClass); }
private static final Banner DEFAULT_BANNER = new SpringBootBanner();
private Banner getBanner(Environment environment, Banner definedBanner) { Banners banners = new Banners(); banners.addIfNotNull(getImageBanner(environment)); banners.addIfNotNull(getTextBanner(environment)); if (banners.hasAtLeastOneBanner()) { return banners; } if (this.fallbackBanner != null) { return this.fallbackBanner; } return DEFAULT_BANNER; }
logger和system.out方式都是通过getBanner方法获取到具体的banner对象，然后进行打印。这里没有配置任何banner，所以使用了默认的banner(SpringBootBanner)。
SpringBootBanner代码如下，从代码就可以看到我们的打印图标了
class SpringBootBanner implements Banner { private static final String[] BANNER = { "", " . ____ _ __ _ _", " /\\\\ / ___'_ __ _ _(_)_ __ __ _ \\ \\ \\ \\", "( ( )\\___ | '_ | '_| | '_ \\/ _` | \\ \\ \\ \\", " \\\\/ ___)| |_)| | | | | || (_| | ) ) ) )", " ' |____| .__|_| |_|_| |_\\__, | / / / /", " =========|_|==============|___/=/_/_/_/" }; private static final String SPRING_BOOT = " :: Spring Boot :: "; private static final int STRAP_LINE_SIZE = 42; @Override public void printBanner(Environment environment, Class<?> sourceClass, PrintStream printStream) { for (String line : BANNER) { printStream.println(line); } String version = SpringBootVersion.getVersion(); version = (version == null ? "" : " (v" + version + ")"); String padding = ""; while (padding.length() < STRAP_LINE_SIZE - (version.length() + SPRING_BOOT.length())) { padding += " "; } printStream.println(AnsiOutput.toString(AnsiColor.GREEN, SPRING_BOOT, AnsiColor.DEFAULT, padding, AnsiStyle.FAINT, version)); printStream.println(); } }
printBanner方法将图标和springboot 名字和版本信息格式化输出。程序启动后即可以看到如下画面
到这里，程序启动输出的第一个信息出来了。。。接下来的方法就是创建Application应用上下文具体内容了。。。。
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