前言
之前的文章我们分析了SpringApplication#run方法执行的前4步,这里我们分析第5步,打印banner.
解析
SpringApplication#run方法的第5步执行如下代码:
private Banner printBanner(ConfigurableEnvironment environment) { // 1. 首先判断banner的输出级别。如果禁用了，则直接返回空。 if (this.bannerMode == Banner.Mode.OFF) { return null; } // 2. 获取资源加载器ResourceLoader ResourceLoader resourceLoader = this.resourceLoader != null ? this.resourceLoader : new DefaultResourceLoader(getClassLoader()); // 3. 实例化SpringApplicationBannerPrinter类 SpringApplicationBannerPrinter bannerPrinter = new SpringApplicationBannerPrinter( resourceLoader, this.banner); // 如果banner的输出模式是Mode.LOG，则直接将其信息输出到logger日志中，否则将其输出到控制台，也就是System.out if (this.bannerMode == Mode.LOG) { return bannerPrinter.print(environment, this.mainApplicationClass, logger); } return bannerPrinter.print(environment, this.mainApplicationClass, System.out); }做了4件事
- 如果this.bannerMode等于Banner.Mode.OFF,则直接返回空。
获取资源加载器ResourceLoader.代码如下:
ResourceLoader resourceLoader = this.resourceLoader != null ? this.resourceLoader : new DefaultResourceLoader(getClassLoader());对于当前的场景来说, SpringApplication 中的 resourceLoader为null.因此会实例化DefaultResourceLoader.
实例化SpringApplicationBannerPrinter类.代码如下:
SpringApplicationBannerPrinter(ResourceLoader resourceLoader, Banner fallbackBanner) { this.resourceLoader = resourceLoader; this.fallbackBanner = fallbackBanner; }注意.在当前场景下, SpringApplicationBannerPrinter中的fallbackBanner为null.
如果banner的输出模式是Mode.LOG，则直接将其信息输出到logger日志中.
注意
默认情况下. SpringApplication中的banner输出模式为CONSOLE.因此是不会输出到日志的.
banner的输出默认如下:
enum Mode { /** * Disable printing of the banner. */ OFF, /** * Print the banner to System.out. */ CONSOLE, /** * Print the banner to the log file. */ LOG }将banner输出到控制台，也就是System.out.代码如下:
public Banner print(Environment environment, Class<?> sourceClass, PrintStream out) { // 1. 获取Banner Banner banner = getBanner(environment, this.fallbackBanner); // 2. 调用Banner中的printBanner方法 banner.printBanner(environment, sourceClass, out); // 3. 实例化PrintedBanner类 return new PrintedBanner(banner, sourceClass); }做了3件事:
- 获取Banner
- 调用Banner中的printBanner方法.进行banner的打印.
- 实例化PrintedBanner类
获取banner的方法如下:
private Banner getBanner(Environment environment, Banner definedBanner) { Banners banners = new Banners(); banners.addIfNotNull(getImageBanner(environment)); banners.addIfNotNull(getTextBanner(environment)); // 如果Banners对象的banners不为空，也就是至少找到了banner.gif，banner.jpg，banner.png，banner.txt其中的一个，那么返回该Banners对象，否则返回默认的SpringBootBanner对象 if (banners.hasAtLeastOneBanner()) { return banners; } if (this.fallbackBanner != null) { return this.fallbackBanner; } return DEFAULT_BANNER; }做了3件事
- 实例化Banners.然后为其设置ImageBanner和TextBanner.如果此时anners对象的banners不为空.则返回Banners.
- 如果fallbackBanner不为null的话,返回fallbackBanner.对于当前场景来说fallbackBanner为null.
- 返回默认的banner.默认的bannenr为 SpringBootBanner.
这里有必要说明一下banner的继承体系.如下:
其只声明了一个方法.如下:
public interface Banner { /** * Print the banner to the specified print stream. * @param environment the spring environment * @param sourceClass the source class for the application * @param out the output print stream */ void printBanner(Environment environment, Class<?> sourceClass, PrintStream out); }Banners实例化后,会调用getImageBanner方法进行加载.代码如下:
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); } for (String ext : IMAGE_EXTENSION) { Resource resource = this.resourceLoader.getResource("banner." + ext); if (resource.exists()) { return new ImageBanner(resource); } } return null; }逻辑如下:
- 首先判断是否配置了系统属性banner.image.location，如果有直接返回ImageBanner.
如果没有配置则在classpath中查找banner.gif，banner.jpg，banner.png，如果找到，则创建一个ImageBanner对象并添加到Banners对象的banners属性中，该属性是一个List.代码如下:
private final List<Banner> banners = new ArrayList<Banner>(); public void addIfNotNull(Banner banner) { if (banner != null) { this.banners.add(banner); } }
很明显 对于当前场景来说. getImageBanner返回的是null.
接下来调用getTextBanner.来加载TextBanner.代码如下:
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; }还是同样的套路.
- 从environment中获取banner.location属性，默认为banner.txt
- 进行加载.如果存在的话,则返回ResourceBanner.否则返回null.
对于当前场景来说.返回的是null.
因此,对于当前场景来说. getBanner返回的是SpringBootBanner.
接下来调用SpringBootBanner#printBanner方法.代码如下:
private static final String[] BANNER = { "", " . ____ _ __ _ _", " /\\\\ / ___'_ __ _ _(_)_ __ __ _ \\ \\ \\ \\", "( ( )\\___ | '_ | '_| | '_ \\/ _` | \\ \\ \\ \\", " \\\\/ ___)| |_)| | | | | || (_| | ) ) ) )", " ' |____| .__|_| |_|_| |_\\__, | / / / /", " =========|_|==============|___/=/_/_/_/" }; private static final String SPRING_BOOT = " :: Spring Boot :: "; private static final int STRAP_LINE_SIZE = 42; public void printBanner(Environment environment, Class<?> sourceClass, PrintStream printStream) { for (String line : BANNER) { printStream.println(line); } String version = SpringBootVersion.getVersion(); version = (version == null ? "" : " (v" + version + ")"); String padding = ""; while (padding.length() < STRAP_LINE_SIZE - (version.length() + SPRING_BOOT.length())) { padding += " "; } printStream.println(AnsiOutput.toString(AnsiColor.GREEN, SPRING_BOOT, AnsiColor.DEFAULT, padding, AnsiStyle.FAINT, version)); printStream.println(); }做了3件事
- 循环遍历BANNER数组，并依次进行数组内容的打印
调用SpringBootVersion#getVersion，进行springboot版本信息的获取.然后为了与之前的输出字符进行对齐,在springboot版本信息前加空格.SpringBootVersion#getVersion代码如下:
public static String getVersion() { Package pkg = SpringApplication.class.getPackage(); return (pkg != null ? pkg.getImplementationVersion() : null); }通过AnsiOutput#toString方法生成字符.输出到PrintStream.最后输出一个回车换行.
代码如下:
public static String toString(Object... elements) { StringBuilder sb = new StringBuilder(); if (isEnabled()) { buildEnabled(sb, elements); } else { buildDisabled(sb, elements); } return sb.toString(); }- 实例化StringBuilder进行字符串拼接.
判断是否可用.如果可以调用buildEnabled.否则调用buildDisabled. isEnabled方法如下:
private static boolean isEnabled() { if (enabled == Enabled.DETECT) { // 默认走到这里. if (ansiCapable == null) { // 对于当前场景来说.ansiCapable 为 null.因此会执行detectIfAnsiCapable方法 ansiCapable = detectIfAnsiCapable(); } return ansiCapable; } return enabled == Enabled.ALWAYS; }这里用到了我们之前分析过的知识.springApplication run 方法执行前4步的过程中.发送了ApplicationEnvironmentPreparedEvent 时间. 其中AnsiOutputApplicationListener 对该事件进行了处理.代码如下:
public void onApplicationEvent(ApplicationEnvironmentPreparedEvent event) { RelaxedPropertyResolver resolver = new RelaxedPropertyResolver( event.getEnvironment(), "spring.output.ansi."); if (resolver.containsProperty("enabled")) { String enabled = resolver.getProperty("enabled"); AnsiOutput.setEnabled(Enum.valueOf(Enabled.class, enabled.toUpperCase())); } if (resolver.containsProperty("console-available")) { AnsiOutput.setConsoleAvailable( resolver.getProperty("console-available", Boolean.class)); } }对于当前场景来说. resolver中是含有spring.output.ansi.enabled 的配置的.默认为true
因此会将AnsiOutput的enabled 设置为Enabled.ALWAYS.
因此这里会执行buildEnabled方法.代码如下:
private static void buildEnabled(StringBuilder sb, Object[] elements) { boolean writingAnsi = false; boolean containsEncoding = false; for (Object element : elements) { if (element instanceof AnsiElement) { containsEncoding = true; if (!writingAnsi) { sb.append(ENCODE_START); writingAnsi = true; } else { sb.append(ENCODE_JOIN); } } else { if (writingAnsi) { sb.append(ENCODE_END); writingAnsi = false; } } sb.append(element); } if (containsEncoding) { sb.append(writingAnsi ? ENCODE_JOIN : ENCODE_START); sb.append(RESET); sb.append(ENCODE_END); } }这里返回的字符串为
[32m :: Spring Boot :: [39m [2m[0;39m
自定义banner
通过之前的分析,我们知道了SpringApplicationBannerPrinter#getBanner 默认返回的是SpringBootBanner.但是当我们在类路径下 放入banner.txt或者在banner.image.location 放入图片.又该如何呢? 此时返回的是Banners.在打印时会调用Banners#printBanner方法.代码如下:
public void printBanner(Environment environment, Class<?> sourceClass,
PrintStream out) {
for (Banner banner : this.banners) {
banner.printBanner(environment, sourceClass, out);
}
}很简单循环遍历banners调用其printBanner进行打印.那么Banners会有哪些banner呢？由前可知有
- ImageBanner
- ResourceBanner
那么我们就分别看下其printBanner方法.
ImageBanner#printBanner 代码如下:
public void printBanner(Environment environment, Class<?> sourceClass, PrintStream out) { // 1. 获取系统环境变量中的java.awt.headless变量。 String headless = System.getProperty("java.awt.headless"); try { // 2. 设置java.awt.headless变量值为true。并调用printBanner方法进行图案的打印工作 System.setProperty("java.awt.headless", "true"); printBanner(environment, out); } catch (Throwable ex) { logger.warn("Image banner not printable: " + this.image + " (" + ex.getClass() + ": '" + ex.getMessage() + "')"); logger.debug("Image banner printing failure", ex); } finally { // 3. finally中还原操作系统中的java.awt.headless环境变量值 if (headless == null) { System.clearProperty("java.awt.headless"); } else { System.setProperty("java.awt.headless", headless); } } }做了3件事
- 获取系统环境变量中的java.awt.headless变量。
- 设置java.awt.headless变量值为true。并调用printBanner方法进行图案的打印工作
- finally中还原操作系统中的java.awt.headless环境变量值
指定一提的是,java.awt.headless 默认就是true.
printBanner方法代码如下:
private void printBanner(Environment environment, PrintStream out) throws IOException { PropertyResolver properties = new RelaxedPropertyResolver(environment, "banner.image."); int width = properties.getProperty("width", Integer.class, 76); int height = properties.getProperty("height", Integer.class, 0); int margin = properties.getProperty("margin", Integer.class, 2); boolean invert = properties.getProperty("invert", Boolean.class, false); BufferedImage image = readImage(width, height); printBanner(image, margin, invert, out); }还是3件事
- 读取banner.image.width,默认为 76 .
读取banner.image.height,默认为 0 .
读取banner.image.margin,默认为 2.
读取banner.image.invert,默认为 false. 调用readImage 进行图片的读取.代码如下:
private BufferedImage readImage(int width, int height) throws IOException { InputStream inputStream = this.image.getInputStream(); try { BufferedImage image = ImageIO.read(inputStream); return resizeImage(image, width, height); } finally { inputStream.close(); } }通过ImageIO进行读取,最后通过读取图片的配置参数,进行图片的缩放处理.
printBanner 实现如下:
private void printBanner(BufferedImage image, int margin, boolean invert, PrintStream out) { AnsiElement background = (invert ? AnsiBackground.BLACK : AnsiBackground.DEFAULT); out.print(AnsiOutput.encode(AnsiColor.DEFAULT)); out.print(AnsiOutput.encode(background)); out.println(); out.println(); AnsiColor lastColor = AnsiColor.DEFAULT; for (int y = 0; y < image.getHeight(); y++) { for (int i = 0; i < margin; i++) { out.print(" "); } for (int x = 0; x < image.getWidth(); x++) { Color color = new Color(image.getRGB(x, y), false); AnsiColor ansiColor = AnsiColors.getClosest(color); if (ansiColor != lastColor) { out.print(AnsiOutput.encode(ansiColor)); lastColor = ansiColor; } out.print(getAsciiPixel(color, invert)); } out.println(); } out.print(AnsiOutput.encode(AnsiColor.DEFAULT)); out.print(AnsiOutput.encode(AnsiBackground.DEFAULT)); out.println(); }没什么可说的,图片是由一个一个的像素组成的,直接输出每个像素即可.
ResourceBanner#printBanner,代码如下:
public void printBanner(Environment environment, Class<?> sourceClass, PrintStream out) { try { // 1. 获取resource中的输入流，并将其转化为字符串 通过environment获取banner.charset变量，如果不存在，则默认使用UTF-8编码 String banner = StreamUtils.copyToString(this.resource.getInputStream(), environment.getProperty("banner.charset", Charset.class, Charset.forName("UTF-8"))); // 2. 循环遍历所有的PropertyResolver 去解析banner中配置的spel表达式 for (PropertyResolver resolver : getPropertyResolvers(environment, sourceClass)) { banner = resolver.resolvePlaceholders(banner); } // 3. 打印字符串信息 out.println(banner); } catch (Exception ex) { logger.warn("Banner not printable: " + this.resource + " (" + ex.getClass() + ": '" + ex.getMessage() + "')", ex); } }还是3步:
- 获取resource中的输入流，并将其转化为字符串 通过environment获取banner.charset变量，如果不存在，则默认使用UTF-8编码
循环遍历所有的PropertyResolver 去解析banner中配置的spel表达式.
首先通过getPropertyResolvers 获得所有的PropertyResolver.代码如下:
protected List<PropertyResolver> getPropertyResolvers(Environment environment, Class<?> sourceClass) { // 1. 实例化resolvers集合，并添加environment元素，Environment接口继承自PropertyResolver接口 List<PropertyResolver> resolvers = new ArrayList<PropertyResolver>(); resolvers.add(environment); // 2. 调用getVersionResolver(sourceClass)方法并将其返回值添加到resolvers集合 resolvers.add(getVersionResolver(sourceClass)); // 3. 调用getAnsiResolver(sourceClass)方法并将其返回值添加到resolvers集合 直接设置开启了ansi resolvers.add(getAnsiResolver()); // 4. 调用getTitleResolver(sourceClass)方法并将其返回值添加到resolvers集合 resolvers.add(getTitleResolver(sourceClass)); return resolvers; }4件事:
- 实例化resolvers集合，并添加environment元素，Environment接口继承自PropertyResolver接口
调用getVersionResolver(sourceClass)方法并将其返回值添加到resolvers集合
代码如下:
private PropertyResolver getVersionResolver(Class<?> sourceClass) { MutablePropertySources propertySources = new MutablePropertySources(); propertySources .addLast(new MapPropertySource("version", getVersionsMap(sourceClass))); return new PropertySourcesPropertyResolver(propertySources); }其构建了一个MapPropertySource,名为version,value是通过getVersionsMap方法获得的.最后返回一个PropertySourcesPropertyResolver.代码如下:
private Map<String, Object> getVersionsMap(Class<?> sourceClass) { // 获取sourceClass所在包的版本号 String appVersion = getApplicationVersion(sourceClass); // 获取Boot版本号 String bootVersion = getBootVersion(); Map<String, Object> versions = new HashMap<String, Object>(); versions.put("application.version", getVersionString(appVersion, false)); versions.put("spring-boot.version", getVersionString(bootVersion, false)); versions.put("application.formatted-version", getVersionString(appVersion, true)); versions.put("spring-boot.formatted-version", getVersionString(bootVersion, true)); return versions; } protected String getApplicationVersion(Class<?> sourceClass) { Package sourcePackage = (sourceClass == null ? null : sourceClass.getPackage()); return (sourcePackage == null ? null : sourcePackage.getImplementationVersion()); } protected String getBootVersion() { return SpringBootVersion.getVersion(); } private String getVersionString(String version, boolean format) { if (version == null) { return ""; } return (format ? " (v" + version + ")" : version); }逻辑如下:
- 首先通过调用getApplicationVersion方法获得appVersion.其是通过获取sourceClass所在包的版本号. sourceClass为应用的启动类
- 获取Boot版本号.同样是通过获得SpringApplication所在包的版本号完成的
- 在map中存入数据.
该方法最终的数据为:
{application.formatted-version=, application.version=, spring-boot.formatted-version=, spring-boot.version=}
调用getAnsiResolver(sourceClass)方法并将其返回值添加到resolvers集合 直接设置开启了ansi.代码如下:
private PropertyResolver getAnsiResolver() { MutablePropertySources sources = new MutablePropertySources(); sources.addFirst(new AnsiPropertySource("ansi", true)); return new PropertySourcesPropertyResolver(sources); }调用getTitleResolver(sourceClass)方法并将其返回值添加到resolvers集合.代码如下:
private PropertyResolver getTitleResolver(Class<?> sourceClass) { MutablePropertySources sources = new MutablePropertySources(); String applicationTitle = getApplicationTitle(sourceClass); // 获取当前启动类中所在的包中的Implementation-Title属性值，并将其添加到sources中。 Map<String, Object> titleMap = Collections.<String, Object>singletonMap("application.title", (applicationTitle == null ? "" : applicationTitle)); sources.addFirst(new MapPropertySource("title", titleMap)); return new PropertySourcesPropertyResolver(sources); }调用getApplicationTitle获得title.代码如下:
protected String getApplicationTitle(Class<?> sourceClass) { Package sourcePackage = (sourceClass == null ? null : sourceClass.getPackage()); return (sourcePackage == null ? null : sourcePackage.getImplementationTitle()); }打印字符串信息
