上篇回顾
上一篇prepareEnvironment()准备环境主要分析了StandardServletEnvironment的创建, 以及系统属性, 环境变量, 配置文件等属性文件的加载顺序
目录
1. 打印Banner printBanner()
2. SpringApplicationBannerPrinter
3. 总结
1. 打印Banner printBanner()
- 实例化ResourceLoader, 默认为null, 所以实例化一个DefaultResourceLoader
- 实例化一个SpringApplicationBannerPrinter对象
- 调用SpringApplicationBannerPrinter的print方法
public class SpringApplication {
public ConfigurableApplicationContext run(String... args) {
StopWatch stopWatch = new StopWatch();
stopWatch.start();
ConfigurableApplicationContext context = null;
Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
configureHeadlessProperty();
SpringApplicationRunListeners listeners = getRunListeners(args);
listeners.starting();
try {
ApplicationArguments applicationArguments = new DefaultApplicationArguments(
args);
ConfigurableEnvironment environment = prepareEnvironment(listeners,
applicationArguments);
configureIgnoreBeanInfo(environment);
//本文的重点
//打印Banner
Banner printedBanner = printBanner(environment);
//....
}
//打印Banner
private Banner printBanner(ConfigurableEnvironment environment) {
//如果Mode为OFF
//那么不打印Banner
if (this.bannerMode == Banner.Mode.OFF) {
return null;
}
//ResourceLoader资源加载类
//默认为DefaultResourceLoader
ResourceLoader resourceLoader = (this.resourceLoader != null)
? this.resourceLoader : new DefaultResourceLoader(getClassLoader());
//实例化一个SpringApplicationBannerPrinter
SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter(
resourceLoader, this.banner);
//调用SpringApplicationBannerPrinter#print方法打印Banner
if (this.bannerMode == Mode.LOG) {
//日志打印Banner
return bannerPrinter.print(environment, this.mainApplicationClass, logger);
}
//控制台打印Banner
return bannerPrinter.print(environment, this.mainApplicationClass, System.out);
}
}
2. SpringApplicationBannerPrinter
SpringApplicationBannerPrinter打印banner过程分为5步
- 加载图片Banner
- 先加载spring.banner.image.location指定的图片Banner
- 不存在的话, 分别取加载classpath下banner.gif, banner.jpg和banner.png
- 实例化为ImageBanner, 维护到Banners对象中
- 加载文本Banner
- 先加载spring.banner.location指定的文本banner
- 不存在的话, 加载classpath下的banner.txt文本
- 实例化一个ResourceBanner, 维护到Banners对象中
- 图片和文本Banner都不存在的话, 如果通过构造函数, 传入了fallbackBanner, 那么返回fallbackBanner
- 图片, 文本和fallbackBanner都不存在, 那么返回默认的SpringBootBanner
- 打印Banner, 返回一个PrintedBanner
- 如果Banners列表中同时存在图片和文本Banner,那么都会打印出来
class SpringApplicationBannerPrinter {
//文本banner位置
static final String BANNER_LOCATION_PROPERTY = "spring.banner.location";
//图片banner位置
static final String BANNER_IMAGE_LOCATION_PROPERTY = "spring.banner.image.location";
//默认banner名称
static final String DEFAULT_BANNER_LOCATION = "banner.txt";
//支持的图片扩展名
static final String[] IMAGE_EXTENSION = { "gif", "jpg", "png" };
//默认banner类
private static final Banner DEFAULT_BANNER = new SpringBootBanner();
//日志打印Banner
public Banner print(Environment environment, Class<?> sourceClass, Log logger) {
//获取banner
Banner banner = getBanner(environment);
try {
//打印Banner
logger.info(createStringFromBanner(banner, environment, sourceClass));
}
catch (UnsupportedEncodingException ex) {
logger.warn("Failed to create String for banner", ex);
}
return new PrintedBanner(banner, sourceClass);
}
//控制台打印Banner
public Banner print(Environment environment, Class<?> sourceClass, PrintStream out) {
//获取到Banners对象, 其中维护了Banner列表
//如果Banners中没有对象, 那么判断fallbackBanner
//如果都没有的话,返回默认的SpringBootBanner
Banner banner = getBanner(environment);
//一次打印Banner
banner.printBanner(environment, sourceClass, out);
return new PrintedBanner(banner, sourceClass);
}
//获取Banner
//Banners类保存多个banner列表
private Banner getBanner(Environment environment) {
//获取Banners列表
Banners banners = new Banners();
//添加ImageBanner
banners.addIfNotNull(getImageBanner(environment));
//添加TextBanner
banners.addIfNotNull(getTextBanner(environment));
if (banners.hasAtLeastOneBanner()) {
//如果有自定义Banner,则立即返回
return banners;
}
if (this.fallbackBanner != null) {
//如果构造函数传参过来
//也就是通过java自定义了fallbackBanner
//那么返回fallbackBanner
return this.fallbackBanner;
}
//如果没有的话, 返回默认Banner, SpringBootBanner
return DEFAULT_BANNER;
}
//获取文本banner
private Banner getTextBanner(Environment environment) {
//优先获取spring.banner.location指定的banner位置
//然后查找classpath下的banner.txt
String location = environment.getProperty(BANNER_LOCATION_PROPERTY,
DEFAULT_BANNER_LOCATION);
Resource resource = this.resourceLoader.getResource(location);
if (resource.exists()) {
//存在的话,立即返回ResourceBanner
return new ResourceBanner(resource);
}
//都没有的话,返回null
return null;
}
//获取图片banner
private Banner getImageBanner(Environment environment) {
//优先获取spring.banner.image.location指定的图片banner
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) {
//如果没有指定spring.banner.image.location
//那么查找classpath下的banner.jpg, banner.png, banner.gif
Resource resource = this.resourceLoader.getResource("banner." + ext);
if (resource.exists()) {
//有一个存在的话,立即返回该Banner
return new ImageBanner(resource);
}
}
//都不存在的话返回null
return null;
}
}
3. 总结
打印Banner执行步骤如下:
- 首先加载图片Banner
- 然后加载文本Banner
- 再判断fallbackBanner
- 最后返回默认的SpringBootBanner
- 打印Banner, 返回一个PrintedBanner对象
下一篇
我们将会在下一篇createApplicationContext()创建应用上下文, 继续阅读springboot源码
