Springboot banner

Banner的实现类如下：

SpringBootBanner：Banner的默认实现类
ImageBanner：用来打印图片日志的banner
ResourceBanner:资源Banner

Springboot在启动的时候，默认情况下会打印如下信息

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.5.RELEASE)

可以分析源码看看为什么打印如下日志

SpringApplication中run方法

public ConfigurableApplicationContext run(String... args) {
            ...
            Banner printedBanner = printBanner(environment);
            ....
        return context;
    }

调用printBanner(ConfigurableEnvironment environment)的方法

private Banner printBanner(ConfigurableEnvironment environment) {
        if (this.bannerMode == Banner.Mode.OFF) {
            return null;
        }
    //获取资源加载
        ResourceLoader resourceLoader = (this.resourceLoader != null) ? this.resourceLoader
                : new DefaultResourceLoader(getClassLoader());
    //创建SpringApplicationBannerPrinter对象
        SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter(resourceLoader, this.banner);
        if (this.bannerMode == Mode.LOG) {
            return bannerPrinter.print(environment, this.mainApplicationClass, logger);
        }
    //打印日志
        return bannerPrinter.print(environment, this.mainApplicationClass, System.out);
    }

Banner print(Environment environment, Class<?> sourceClass, PrintStream out) {
        //获取Banner
        Banner banner = getBanner(environment);
        //打印Banner
        banner.printBanner(environment, sourceClass, out);
        return new PrintedBanner(banner, sourceClass);
    }

getBanner(Environment environment)方法

private Banner getBanner(Environment environment) {
    Banners banners = new Banners();
    //添加ImageBanner
    banners.addIfNotNull(getImageBanner(environment));
    //添加TextBanner
    banners.addIfNotNull(getTextBanner(environment));
    if (banners.hasAtLeastOneBanner()) {
        return banners;
    }
    if (this.fallbackBanner != null) {
        return this.fallbackBanner;
    }
    return DEFAULT_BANNER;
}

static final String BANNER_IMAGE_LOCATION_PROPERTY = "spring.banner.image.location";
static final String[] IMAGE_EXTENSION = { "gif", "jpg", "png" };
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;
        }
    //获取banner.gif，banner.jpg,banner.png
        for (String ext : IMAGE_EXTENSION) {
            Resource resource = this.resourceLoader.getResource("banner." + ext);
            if (resource.exists()) {
                return new ImageBanner(resource);
            }
        }
        return null;
    }

    static final String BANNER_LOCATION_PROPERTY = "spring.banner.location";
    static final String DEFAULT_BANNER_LOCATION = "banner.txt";
private Banner getTextBanner(Environment environment) {
    //获取路径下的banner.txt;
        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;
    }

通过上面的代码可以知道，如果在classpath路径下面添加了banner.txt,banner.jpg文件后，首先加载banner.jpg，然后加载banner.txt文件，后面都会打印出来。

下面通实现自己的Banner

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        //SpringApplication.run(Application.class,args);
    
        SpringApplication application=new SpringApplication(Application.class);
        //关闭banner
       // application.setBannerMode(Banner.Mode.OFF);
        application.setBanner(new Mybanner());
        application.run(args);

//        SpringApplicationBuilder applicationBuilder=new SpringApplicationBuilder();
//        //applicationBuilder.profiles("");
//        applicationBuilder.bannerMode(Banner.Mode.OFF).run(args);

    }

}

public class Mybanner implements Banner {

    private static final String BANNER = "Spring Mybanner";
    @Override
    public void printBanner(Environment environment, Class<?> sourceClass, PrintStream out) {
    
        System.out.println(BANNER);
    }

}

来源：https://www.cnblogs.com/haizhilangzi/p/12443824.html

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