在Spring项目中使用SpringBoot的Banner打印功能

在SpringBoot中有一个打印Banner的功能，只用在Classpath下添加字符文件，就可以在启动时候打印。但是如果当前的项目是Spring项目，该如何添加这个功能呢？
首先在pom.xml文件中添加SpringBoot的依赖

<properties>
	<springframework.version>4.3.5.RELEASE</springframework.version>
	<springboot.version>2.2.2.RELEASE</springboot.version>
	<maven.compiler.encoding>UTF-8</maven.compiler.encoding>
	<jdk.source.veriosn>1.8</jdk.source.veriosn>
	<jdk.target.veriosn>1.8</jdk.target.veriosn>
</properties>

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-framework-bom</artifactId>
			<version>${springframework.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
		<dependency>
			<!-- Import dependency management from Spring Boot -->
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-dependencies</artifactId>
			<version>${springboot.version}</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>
	<dependencies>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
		</dependency>
	</dependencies>

SpringBoot的源码如下：
在org.springframework.boot.SpringApplication类中

	/**
	 * Default banner location.
	 */
	public static final String BANNER_LOCATION_PROPERTY_VALUE = SpringApplicationBannerPrinter.DEFAULT_BANNER_LOCATION;

	/**
	 * Banner location property key.
	 */
	public static final String BANNER_LOCATION_PROPERTY = SpringApplicationBannerPrinter.BANNER_LOCATION_PROPERTY;

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);
			// 打印Banner
			Banner printedBanner = printBanner(environment);
			context = createApplicationContext();
			exceptionReporters = getSpringFactoriesInstances(SpringBootExceptionReporter.class,
					new Class[] { ConfigurableApplicationContext.class }, context);
			prepareContext(context, environment, listeners, applicationArguments, printedBanner);
			refreshContext(context);
			afterRefresh(context, applicationArguments);
			stopWatch.stop();
			if (this.logStartupInfo) {
				new StartupInfoLogger(this.mainApplicationClass).logStarted(getApplicationLog(), stopWatch);
			}
			listeners.started(context);
			callRunners(context, applicationArguments);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, listeners);
			throw new IllegalStateException(ex);
		}

		try {
			listeners.running(context);
		}
		catch (Throwable ex) {
			handleRunFailure(context, ex, exceptionReporters, null);
			throw new IllegalStateException(ex);
		}
		return context;
	}


	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);
	}

但是很遗憾 用于打印的org.springframework.boot.SpringApplicationBannerPrinter类和默认的Banner类SpringBootBanner都定义是包内访问级别，因此拷贝这两个类到本地项目中任意一个包内。然后在同一个包内添加一个工具类：

import org.springframework.core.env.Environment;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.core.io.ResourceLoader;

public class TestBanner {
	public static void printBanner() {
		ResourceLoader resourceLoader = new DefaultResourceLoader();
		Environment environment = new StandardEnvironment();
		SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter(resourceLoader, null);
		bannerPrinter.print(environment, null, System.out);
	}
}

然后在需要打印banner的地方引用这个工具类即可。如果想自定义banner,只需要将文件存放到classpath目录下即可。

https://www.bootschool.net/ascii-art/search
可以在上面的网站查找banner，比如搜索 美女

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