Banner
使用Spring Boot启动的jar包总是会显示一个Spring的图标。实际我们是可以自定义这个图标。Banner接口定义了打印banner的方法。
void printBanner(Environment environment, Class<?> sourceClass, PrintStream out); SpringApplicationBannerPrinter
springboot用来创建banner对象的类，核心方法为getBanner即获取Banner对象。
private Banner getBanner(Environment environment) {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;}
getImageBanner和getTextBanner方法从相应的位置获取资源，然后使用响应的Banner打印相应资源。
private Banner getTextBanner(Environment environment) {String location = environment.getProperty(BANNER_LOCATION_PROPERTY,DEFAULT_BANNER_LOCATION);Resource resource = this.resourceLoader.getResource(location);if (resource.exists()) {return new ResourceBanner(resource);}return null;}private Banner getImageBanner(Environment environment) {String location = environment.getProperty(BANNER_IMAGE_LOCATION_PROPERTY);if (StringUtils.hasLength(location)) {Resource resource = this.resourceLoader.getResource(location);return (resource.exists() ? new ImageBanner(resource) : null);}for (String ext : IMAGE_EXTENSION) {Resource resource = this.resourceLoader.getResource("banner." + ext);if (resource.exists()) {return new ImageBanner(resource);}}return null;}
SpringBootBanner
SpringBootBanner是Banner的实现类，打印一个spring的图样。
ResourceBanner
读取资源，替换占位符，然后打印到相应io。
public void printBanner(Environment environment, Class<?> sourceClass,PrintStream out) {try {String banner = StreamUtils.copyToString(this.resource.getInputStream(),environment.getProperty("banner.charset", Charset.class,StandardCharsets.UTF_8));for (PropertyResolver resolver : getPropertyResolvers(environment,sourceClass)) {banner = resolver.resolvePlaceholders(banner);}out.println(banner);}catch (Exception ex) {logger.warn("Banner not printable: " + this.resource + " (" + ex.getClass()+ ": '" + ex.getMessage() + "')", ex);}}
ImageBanner
读取图片资源，然后打印到相应io。
