Spring Boot banner详解

悠悠 2024-03-16 15:10 50阅读 0赞

> Spring Boot 3.x系列文章
> 
> 1.  [Spring Boot 2.7.8 中文参考指南(一)][Spring Boot 2.7.8]
> 2.  [Spring Boot 2.7.8 中文参考指南(二)-Web][Spring Boot 2.7.8 _-Web]
> 3.  [Spring Boot 源码阅读初始化环境搭建][Spring Boot]
> 4.  [Spring Boot 框架整体启动流程详解][Spring Boot 1]
> 5.  [Spring Boot 系统初始化器详解][Spring Boot 2]
> 6.  [Spring Boot 监听器详解][Spring Boot 3]
> 7.  [Spring Boot banner详解][Spring Boot banner]

## 自定义banner ##

Spring Boot 默认打印的banner是这样的，Java工程师看都看腻了。  
![在这里插入图片描述][f21281a07cac459784200c40c111663b.png]

一般的公司如果有自己脚手架，都会选择自定义banner，放一个公司Logo或者框架别名。

### 简易版banner ###

首先生成一个自己的banner，比如我生成的  
![在这里插入图片描述][9a4d903bbcf247b0a5fcba7f9531c4f3.png]

> 生成的网站很多，可以用"banner 生成器"自行搜索

把生成的内容copy到txt中，命名为"`banner.txt`"（UTF-8），然后放到`resources`下。  
启动Spring Boot 即可看到效果。

![在这里插入图片描述][73aaaadea4854fa1889b4daf22b950ec.png]

### 自定义banner路径 ###

上述的banner.txt 只能放在`resources`根目录下，不能在resources子目录或其他的目录，使用`spring.banner.location`指定该文件的路径，如果该文件不是UTF-8编码，使用`spring.banner.charset`指定文件编码，比如我将文件放到resources的子目录static中。

![在这里插入图片描述][fd9e39e514d84c99934be702c4b66cde.png]

### 自定义banner 样式 ###

光一个Logo也还是太单调，如果能再打印个Spring Boot 版本、应用程序版本就更好了，Spring Boot 都给我们提供了相关变量，可以在banner.txt中使用。

*  $\{application.version\} 应用程序版本
 *  $\{application.formatted-version\} 格式化的应用程序版本，前缀是`v`
 *  $\{spring-boot.version\} Spring Boot框架版本
 *  $\{spring-boot.formatted-version\} 格式化的Spring Boot框架版本，前缀是`v`
 *  $\{Ansi.NAME\} (or $\{AnsiColor.NAME\}, $\{AnsiBackground.NAME\}, $\{AnsiStyle.NAME\})  
    给文字加颜色，加背景，加样式，NAME的值可以在这里获取[ansi][]
 *  $\{application.title\} 应用程序的标题

如图我给banner 加上了颜色，加上了版本

![在这里插入图片描述][4772b4e170f844eb85425babe54e9654.png]  
配置如下：

${AnsiColor.GREEN}
      /$$$$$$   /$$$$$$  /$$$$$$$  /$$   /$$       /$$$$$$ /$$$$$$$$ /$$$$$$   /$$$$$$  /$$     /$$ /$$$$$$   /$$$$$$  /$$     /$$
     /$$__  $$ /$$__  $$| $$__  $$| $$$ | $$      |_  $$_/|__  $$__//$$__  $$ /$$__  $$|  $$   /$$//$$__  $$ /$$__  $$|  $$   /$$/
    | $$  \__/| $$  \__/| $$  \ $$| $$$$| $$        | $$     | $$  | $$  \__/| $$  \ $$ \  $$ /$$/| $$  \__/| $$  \ $$ \  $$ /$$/
    | $$      |  $$$$$$ | $$  | $$| $$ $$ $$ /$$$$$$| $$     | $$  |  $$$$$$ | $$$$$$$$  \  $$$$/ |  $$$$$$ | $$$$$$$$  \  $$$$/
    | $$       \____  $$| $$  | $$| $$  $$$$|______/| $$     | $$   \____  $$| $$__  $$   \  $$/   \____  $$| $$__  $$   \  $$/
    | $$    $$ /$$  \ $$| $$  | $$| $$\  $$$        | $$     | $$   /$$  \ $$| $$  | $$    | $$    /$$  \ $$| $$  | $$    | $$
    |  $$$$$$/|  $$$$$$/| $$$$$$$/| $$ \  $$       /$$$$$$   | $$  |  $$$$$$/| $$  | $$    | $$   |  $$$$$$/| $$  | $$    | $$
     \______/  \______/ |_______/ |__/  \__/      |______/   |__/   \______/ |__/  |__/    |__/    \______/ |__/  |__/    |__/
    ${AnsiColor.DEFAULT}
    ::Spring Boot Version: ${AnsiColor.RED}${spring-boot.formatted-version}${AnsiColor.DEFAULT}
    ::Application Version: ${AnsiColor.RED}${application.formatted-version}${AnsiColor.DEFAULT}

>  *  如果颜色不起作用，那就是需要开启一下：`spring.output.ansi.enabled=always`
>  *  $\{AnsiColor.DEFAULT\} 是将颜色重置，防止前面的颜色影响下面的
>  *  $\{application.formatted-version\} 、 $\{application.version\}、 $\{application.title\} 要使用jar包启动才会打印
>  *  banner.txt 中可以配置环境变量environment中的任何键值

### 使用图片做banner ###

在Spring Boot 3.x版本中已经不被支持

### 编码方式定义banner ###

自定义一个CustomBanner类，实现`Banner接口`，如：

import org.springframework.boot.Banner;
    import org.springframework.core.env.Environment;
    
    import java.io.PrintStream;
    
    public class CustomBanner implements Banner {
        
    
        public static final String BANNER = "  /$$$$$$   /$$$$$$  /$$$$$$$  /$$   /$$       /$$$$$$ /$$$$$$$$ /$$$$$$   /$$$$$$  /$$     /$$ /$$$$$$   /$$$$$$  /$$     /$$\n" +
                " /$$__  $$ /$$__  $$| $$__  $$| $$$ | $$      |_  $$_/|__  $$__//$$__  $$ /$$__  $$|  $$   /$$//$$__  $$ /$$__  $$|  $$   /$$/\n" +
                "| $$  \\__/| $$  \\__/| $$  \\ $$| $$$$| $$        | $$     | $$  | $$  \\__/| $$  \\ $$ \\  $$ /$$/| $$  \\__/| $$  \\ $$ \\  $$ /$$/ \n" +
                "| $$      |  $$$$$$ | $$  | $$| $$ $$ $$ /$$$$$$| $$     | $$  |  $$$$$$ | $$$$$$$$  \\  $$$$/ |  $$$$$$ | $$$$$$$$  \\  $$$$/  \n" +
                "| $$       \\____  $$| $$  | $$| $$  $$$$|______/| $$     | $$   \\____  $$| $$__  $$   \\  $$/   \\____  $$| $$__  $$   \\  $$/   \n" +
                "| $$    $$ /$$  \\ $$| $$  | $$| $$\\  $$$        | $$     | $$   /$$  \\ $$| $$  | $$    | $$    /$$  \\ $$| $$  | $$    | $$    \n" +
                "|  $$$$$$/|  $$$$$$/| $$$$$$$/| $$ \\  $$       /$$$$$$   | $$  |  $$$$$$/| $$  | $$    | $$   |  $$$$$$/| $$  | $$    | $$    \n" +
                " \\______/  \\______/ |_______/ |__/  \\__/      |______/   |__/   \\______/ |__/  |__/    |__/    \\______/ |__/  |__/    |__/    \n";
    
        @Override
        public void printBanner(Environment environment, Class<?> sourceClass, PrintStream printStream) {
        
            printStream.println(BANNER);
        }
    }

SpringApplication 中配置banner

SpringApplication springApplication = new SpringApplication(SpringBootDemoApplication.class);
    springApplication.setBanner(new CustomBanner());

> 如果在类路径中存在`banner.txt` 在会优先使用`banner.txt`

### 禁用banner ###

Spring Boot 提供了`spring.main.banner-mode`配置，`OFF`\-关闭banner打印，`CONSOLE`\-使用System.out打印banner，log文件不会记录，`LOG`\-打印到log文件

另外同样可以用`springApplication.setBannerMode(Banner.Mode.OFF);`方式设置banner

## 加载打印原理 ##

在之前的《[Spring Boot 框架整体启动流程详解][Spring Boot 4]》中，我们看到有一步是

//打印banner
    Banner printedBanner = printBanner(environment);

这一步就是加载打印banner的核心。

private Banner printBanner(ConfigurableEnvironment environment) {
        
    //如果bannerMode是关闭的，就会不打印banner
    	if (this.bannerMode == Banner.Mode.OFF) {
        
    		return null;
    	}
    	//获取资源加载器，如果当前没有就使用默认的资源加载器
    	ResourceLoader resourceLoader = (this.resourceLoader != null) ? this.resourceLoader
    			: new DefaultResourceLoader(null);
    //创建一个SpringBoot应用程序的banner打印类，如果通过setBanner设置，this.banner会有值
    	SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter(resourceLoader, this.banner);
    	//如果bannerMode 是打印到log文件
    	if (this.bannerMode == Mode.LOG) {
        
    		return bannerPrinter.print(environment, this.mainApplicationClass, logger);
    	}
    	//默认打印到控制台
    	return bannerPrinter.print(environment, this.mainApplicationClass, System.out);
    }

先看下如何打印到log文件：

Banner print(Environment environment, Class<?> sourceClass, Log logger) {
        
    //获取Banner对象
    	Banner banner = getBanner(environment);
    	try {
        
    	//使用log 的info 级别打印
    		logger.info(createStringFromBanner(banner, environment, sourceClass));
    	}
    	catch (UnsupportedEncodingException ex) {
        
    		logger.warn("Failed to create String for banner", ex);
    	}
    	//创建一个打印banner的装饰器bean，允许后期再次使用
    	return new PrintedBanner(banner, sourceClass);
    }

如何获取的Banner对象：

private Banner getBanner(Environment environment) {
        
    //获取txt文本banner
    	Banner textBanner = getTextBanner(environment);
    	if (textBanner != null) {
        
    		return textBanner;
    	}
    	//fallbackBanner 为前期通过setBanner设置的自定义banner
    	//可见如果两者同时设置，优先使用的txt文本banner
    	if (this.fallbackBanner != null) {
        
    		return this.fallbackBanner;
    	}
    	//都没有，返回一个默认的SpringBootBanner
    	return DEFAULT_BANNER;
    }

如果获取txt文本banner：

private Banner getTextBanner(Environment environment) {
        
    //从环境变量中获取spring.banner.location指定的banner地址，如果没有，使用banner.txt
    	String location = environment.getProperty(BANNER_LOCATION_PROPERTY, DEFAULT_BANNER_LOCATION);
    	//获取指定的资源对象
    	Resource resource = this.resourceLoader.getResource(location);
    	try {
        
    	//资源存在，并且资源路径中不包含liquibase-core
    		if (resource.exists() && !resource.getURL().toExternalForm().contains("liquibase-core")) {
        
    		//创建一个从源打印的banner对象，实现了Banner接口
    			return new ResourceBanner(resource);
    		}
    	}
    	catch (IOException ex) {
        
    		// Ignore
    	}
    	return null;
    }

获取到文本banner的ResourceBanner资源对象后，回到`print(Environment environment, Class<?> sourceClass, Log logger)`这个方法中，接下来就是要把获取到banner对象打印出来，`createStringFromBanner`将获取到banner对象，调用其中的`printBanner`方法，把输出流转为UTF-8的字符串输出到log文件中。

private String createStringFromBanner(Banner banner, Environment environment, Class<?> mainApplicationClass)
    		throws UnsupportedEncodingException {
        
    	ByteArrayOutputStream baos = new ByteArrayOutputStream();
    	banner.printBanner(environment, mainApplicationClass, new PrintStream(baos));
    	String charset = environment.getProperty("spring.banner.charset", "UTF-8");
    	return baos.toString(charset);
    }

ResourceBanner的printBanner方法：

public void printBanner(Environment environment, Class<?> sourceClass, PrintStream out) {
        
    	try {
        
    	//从流读取banner.txt 字符串，使用spring.banner.charset编码，或者UTF-8
    		String banner = StreamUtils.copyToString(this.resource.getInputStream(),
    				environment.getProperty("spring.banner.charset", Charset.class, StandardCharsets.UTF_8));
    				//获取用于解析占位符的所有属性源
    		for (PropertyResolver resolver : getPropertyResolvers(environment, sourceClass)) {
        
    		//解析banner，使用PropertyPlaceholderHelper工具类解析
    			banner = resolver.resolvePlaceholders(banner);
    		}
    		//输出到流中
    		out.println(banner);
    	}
    	catch (Exception ex) {
        
    		logger.warn(LogMessage.format("Banner not printable: %s (%s: '%s')", this.resource, ex.getClass(),
    				ex.getMessage()), ex);
    	}
    }

`bannerPrinter.print(environment, this.mainApplicationClass, System.out);`  
打印到控制台的逻辑也是一样的，只是直接输出到控制台

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

## 总结 ##

### 通过图来总结一下整个流程   ![在这里插入图片描述][a0bb22c76bbb4342845b6a69890e8a1a.jpeg] ###

> 作者其他要推荐的文章，欢迎来学习：  
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[Spring Boot 2.7.8]: https://itsaysay.blog.csdn.net/article/details/128922165
[Spring Boot 2.7.8 _-Web]: https://itsaysay.blog.csdn.net/article/details/129338886
[Spring Boot]: https://itsaysay.blog.csdn.net/article/details/129665897
[Spring Boot 1]: https://itsaysay.blog.csdn.net/article/details/130981611
[Spring Boot 2]: https://itsaysay.blog.csdn.net/article/details/131034991
[Spring Boot 3]: https://itsaysay.blog.csdn.net/article/details/131073017
[Spring Boot banner]: https://itsaysay.blog.csdn.net/article/details/131116036
[f21281a07cac459784200c40c111663b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/16/3830b6dfb57e4ea8adc4b45fe073f544.png
[9a4d903bbcf247b0a5fcba7f9531c4f3.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/16/92d95e583df049ecb2f828dd48eeec09.png
[73aaaadea4854fa1889b4daf22b950ec.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/16/e3c9511de6c74b46bfd13d29fc83078e.png
[fd9e39e514d84c99934be702c4b66cde.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/16/4bd217fd80764b58b13996bfcbffdaf0.png
[ansi]: https://github.com/spring-projects/spring-boot/tree/v3.1.0/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/ansi
[4772b4e170f844eb85425babe54e9654.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/16/3744b47fd29646be8c7f0fed423c579b.png
[Spring Boot 4]: https://blog.csdn.net/qq_31635851/article/details/120428850
[a0bb22c76bbb4342845b6a69890e8a1a.jpeg]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/16/6763a3de9eb5423e940c0e14b28c7c9f.png
[Prometheus]: https://itsaysay.blog.csdn.net/article/details/128993876
[PromQL]: https://itsaysay.blog.csdn.net/article/details/128697766
[PromQL 1]: https://itsaysay.blog.csdn.net/article/details/128725788
[PromQL 2]: https://itsaysay.blog.csdn.net/article/details/128734102
[Prometheus 1]: https://itsaysay.blog.csdn.net/article/details/129035181
[Prometheus 2]: https://itsaysay.blog.csdn.net/article/details/129115894
[Prometheus 3]: https://itsaysay.blog.csdn.net/article/details/128741317
[Prometheus 4]: https://itsaysay.blog.csdn.net/article/details/128748383
[Prometheus _Mysql_Mysql]: https://itsaysay.blog.csdn.net/article/details/129248268
[Grafana]: https://itsaysay.blog.csdn.net/article/details/128260639
[Grafana 1]: https://itsaysay.blog.csdn.net/article/details/128280232
[Grafana 2]: https://blog.csdn.net/weixin_40972073/article/details/128292597
[Grafana 3]: https://itsaysay.blog.csdn.net/article/details/128309734
[Grafana 4]: https://itsaysay.blog.csdn.net/article/details/128379173
[Grafana 5]: https://itsaysay.blog.csdn.net/article/details/128586826
[Grafana 6]: https://itsaysay.blog.csdn.net/article/details/128665497
[Spring Boot Admin]: https://itsaysay.blog.csdn.net/article/details/125567451
[SpringBoot Admin]: https://itsaysay.blog.csdn.net/article/details/125302909
[Spring Boot Admin2 _EnableAdminServer]: https://itsaysay.blog.csdn.net/article/details/127986764
[Spring Boot Admin2 AdminServerAutoConfiguration]: https://itsaysay.blog.csdn.net/article/details/127990150
[Spring Boot Admin2]: https://itsaysay.blog.csdn.net/article/details/127992400
[Spring Boot Admin2 _JVM]: https://itsaysay.blog.csdn.net/article/details/128029153
[Spring Boot Admin2 1]: https://itsaysay.blog.csdn.net/article/details/128046695?spm=1001.2014.3001.5502
[Spring Boot Admin _Grafana]: https://itsaysay.blog.csdn.net/article/details/128089324?spm=1001.2014.3001.5502