一、說(shuō)在前面的話

我們之間介紹過(guò)SpringBoot自動(dòng)配置的原理，基本上是如下：

xxxxAutoConfiguration：幫我們給容器中自動(dòng)配置組件；xxxxProperties:配置類來(lái)封裝配置文件的內(nèi)容；

二、靜態(tài)資源映射規(guī)則

1、對(duì)哪些目錄映射？

classpath:/META-INF/resources/ classpath:/resources/classpath:/static/ classpath:/public//：當(dāng)前項(xiàng)目的根路徑

2、什么意思？

就我們?cè)谏厦嫖鍌€(gè)目錄下放靜態(tài)資源（比如：a.js等），可以直接訪問(wèn)（http://localhost:8080/a.js），類似于以前web項(xiàng)目的webapp下；放到其他目錄下無(wú)法被訪問(wèn)。

3、為什么是那幾個(gè)目錄？

3.1、看源碼

我們一起來(lái)讀下源碼，這個(gè)是SpringBoot自動(dòng)配置的WebMvcAutoConfiguration.java類來(lái)幫我們干的。

@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) { if (!this.resourceProperties.isAddMappings()) { logger.debug('Default resource handling disabled'); return; } Integer cachePeriod = this.resourceProperties.getCachePeriod(); if (!registry.hasMappingForPattern('/webjars/**')) { customizeResourceHandlerRegistration(registry.addResourceHandler('/webjars/**') .addResourceLocations('classpath:/META-INF/resources/webjars/').setCachePeriod(cachePeriod)); } String staticPathPattern = this.mvcProperties.getStaticPathPattern(); if (!registry.hasMappingForPattern(staticPathPattern)) { customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern) .addResourceLocations(this.resourceProperties.getStaticLocations()).setCachePeriod(cachePeriod)); }}

3.2、分析源碼

我們重點(diǎn)分析后半截，前半截后面會(huì)介紹。

// staticPathPattern是/**String staticPathPattern = this.mvcProperties.getStaticPathPattern();if (!registry.hasMappingForPattern(staticPathPattern)) { customizeResourceHandlerRegistration( registry.addResourceHandler(staticPathPattern) .addResourceLocations( this.resourceProperties.getStaticLocations()) .setCachePeriod(cachePeriod));}this.resourceProperties.getStaticLocations()========>ResourcePropertiespublic String[] getStaticLocations() { return this.staticLocations;}========>private String[] staticLocations = RESOURCE_LOCATIONS;========>private static final String[] RESOURCE_LOCATIONS;private static final String[] SERVLET_RESOURCE_LOCATIONS = { '/' };private static final String[] CLASSPATH_RESOURCE_LOCATIONS = { 'classpath:/META-INF/resources/', 'classpath:/resources/', 'classpath:/static/', 'classpath:/public/' };========>static { // 可以看到如下是對(duì)上面兩個(gè)數(shù)組進(jìn)行復(fù)制操作到一個(gè)新數(shù)組上，也就是合并。 RESOURCE_LOCATIONS = new String[CLASSPATH_RESOURCE_LOCATIONS.length + SERVLET_RESOURCE_LOCATIONS.length]; System.arraycopy(SERVLET_RESOURCE_LOCATIONS, 0, RESOURCE_LOCATIONS, 0, SERVLET_RESOURCE_LOCATIONS.length); System.arraycopy(CLASSPATH_RESOURCE_LOCATIONS, 0, RESOURCE_LOCATIONS, SERVLET_RESOURCE_LOCATIONS.length, CLASSPATH_RESOURCE_LOCATIONS.length);}所以上述代碼經(jīng)過(guò)我的翻譯后成為了如下樣子：registry.addResourceHandler('/**').addResourceLocations( 'classpath:/META-INF/resources/', 'classpath:/resources/', 'classpath:/static/', 'classpath:/public/', '/') // 設(shè)置緩存時(shí)間 .setCachePeriod(cachePeriod));

3.3、一句話概括

WebMvcAutoConfiguration類自動(dòng)為我們注冊(cè)了如下目錄為靜態(tài)資源目錄，也就是說(shuō)直接可訪問(wèn)到資源的目錄。

classpath:/META-INF/resources/ classpath:/resources/classpath:/static/ classpath:/public//：當(dāng)前項(xiàng)目的根路徑

優(yōu)先級(jí)從上到下。

所以，如果static里面有個(gè)index.html，public下面也有個(gè)index.html，則優(yōu)先會(huì)加載static下面的index.html，因?yàn)閮?yōu)先級(jí)！

4、默認(rèn)首頁(yè)

PS：就是直接輸入ip:port/項(xiàng)目名稱默認(rèn)進(jìn)入的頁(yè)面。

4.1、看源碼

WebMvcAutoConfiguration.java@Beanpublic WelcomePageHandlerMapping welcomePageHandlerMapping( ResourceProperties resourceProperties) { return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(), this.mvcProperties.getStaticPathPattern());}

4.2、分析源碼

resourceProperties.getWelcomePage()========>public Resource getWelcomePage() { // 遍歷默認(rèn)靜態(tài)資源目錄后面拼接個(gè)index.html的數(shù)組 // 比如：[/static/index.html, /public/index.html等等] for (String location : getStaticWelcomePageLocations()) { Resource resource = this.resourceLoader.getResource(location); try { if (resource.exists()) {resource.getURL();return resource; } } catch (Exception ex) { // Ignore } } return null;}========>// 下面這段代碼通俗易懂，就是給默認(rèn)靜態(tài)資源目錄后面拼接個(gè)index.html并返回，比如：/static/index.htmlprivate String[] getStaticWelcomePageLocations() { String[] result = new String[this.staticLocations.length]; for (int i = 0; i < result.length; i++) { String location = this.staticLocations[i]; if (!location.endsWith('/')) { location = location + '/'; } result[i] = location + 'index.html'; } return result;}

所以上述代碼經(jīng)過(guò)我的翻譯后成為了如下樣子：

return new WelcomePageHandlerMapping( 'classpath:/META-INF/resources/index.html', 'classpath:/resources/index.html', 'classpath:/static/index.html', 'classpath:/public/index.html', '/index.html' , '/**');

4.3、一句話概括

WebMvcAutoConfiguration類自動(dòng)為我們注冊(cè)了如下文件為默認(rèn)首頁(yè)。

classpath:/META-INF/resources/index.htmlclasspath:/resources/index.htmlclasspath:/static/index.html classpath:/public/index.html/index.html

優(yōu)先級(jí)從上到下。

所以，如果static里面有個(gè)index.html，public下面也有個(gè)index.html，則優(yōu)先會(huì)加載static下面的index.html，因?yàn)閮?yōu)先級(jí)！

5、favicon.ico

PS：就是這個(gè)圖標(biāo)。

5.1、看源碼

@Configuration@ConditionalOnProperty(value = 'spring.mvc.favicon.enabled', matchIfMissing = true)public static class FaviconConfiguration { private final ResourceProperties resourceProperties; public FaviconConfiguration(ResourceProperties resourceProperties) { this.resourceProperties = resourceProperties; } @Bean public SimpleUrlHandlerMapping faviconHandlerMapping() { SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping(); mapping.setOrder(Ordered.HIGHEST_PRECEDENCE + 1); mapping.setUrlMap(Collections.singletonMap('**/favicon.ico', faviconRequestHandler())); return mapping; } @Bean public ResourceHttpRequestHandler faviconRequestHandler() { ResourceHttpRequestHandler requestHandler = new ResourceHttpRequestHandler(); requestHandler .setLocations(this.resourceProperties.getFaviconLocations()); return requestHandler; }}

5.2、分析源碼

// 首先可以看到的是可以設(shè)置是否生效，通過(guò)參數(shù)spring.mvc.favicon.enabled來(lái)配置，若無(wú)此參數(shù)，則默認(rèn)是生效的。@ConditionalOnProperty(value = 'spring.mvc.favicon.enabled', matchIfMissing = true)========》// 可以看到所有的**/favicon.ico都是在faviconRequestHandler()這個(gè)方法里找。mapping.setUrlMap(Collections.singletonMap('**/favicon.ico', faviconRequestHandler()));========》faviconRequestHandler().this.resourceProperties.getFaviconLocations()// 就是之前的五個(gè)靜態(tài)資源文件夾。 List<Resource> getFaviconLocations() { List<Resource> locations = new ArrayList<Resource>( this.staticLocations.length + 1); if (this.resourceLoader != null) { for (String location : this.staticLocations) { locations.add(this.resourceLoader.getResource(location)); } } locations.add(new ClassPathResource('/')); return Collections.unmodifiableList(locations);}

5.3、一句話概括

只要把favicon.ico放到如下目錄下，就會(huì)自動(dòng)生效。

classpath:/META-INF/resources/ classpath:/resources/classpath:/static/ classpath:/public//：當(dāng)前項(xiàng)目的根路徑

6、webjars

6.1、看源碼

WebMvcAutoConfiguration@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) { if (!this.resourceProperties.isAddMappings()) { logger.debug('Default resource handling disabled'); return; } Integer cachePeriod = this.resourceProperties.getCachePeriod(); if (!registry.hasMappingForPattern('/webjars/**')) { customizeResourceHandlerRegistration(registry.addResourceHandler('/webjars/**') .addResourceLocations('classpath:/META-INF/resources/webjars/').setCachePeriod(cachePeriod)); } String staticPathPattern = this.mvcProperties.getStaticPathPattern(); if (!registry.hasMappingForPattern(staticPathPattern)) { customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern) .addResourceLocations(this.resourceProperties.getStaticLocations()).setCachePeriod(cachePeriod)); }}

6.2、分析源碼

這次我們來(lái)分析前半截。

Integer cachePeriod = this.resourceProperties.getCachePeriod();if (!registry.hasMappingForPattern('/webjars/**')) { customizeResourceHandlerRegistration( registry.addResourceHandler('/webjars/**') .addResourceLocations( 'classpath:/META-INF/resources/webjars/') .setCachePeriod(cachePeriod));}

6.3、一句話概括

所有/webjars/**都從classpath:/META-INF/resources/webjars/路徑下去找對(duì)應(yīng)的靜態(tài)資源。

6.4、什么是webjars？

就是以jar包的方式引入靜態(tài)資源。

官網(wǎng)地址：http://www.webjars.org/。類似于maven倉(cāng)庫(kù)。

我們可以做個(gè)例子，將jquery引入到項(xiàng)目中

<dependency> <groupId>org.webjars</groupId> <artifactId>jquery</artifactId> <version>3.3.1</version></dependency>

看項(xiàng)目依賴

會(huì)自動(dòng)為我們引入jquery，要怎么使用呢？我們上面說(shuō)過(guò)：

所有/webjars/*都從classpath:/META-INF/resources/webjars/路徑下去找對(duì)應(yīng)的靜態(tài)資源。

所以我們啟動(dòng)項(xiàng)目，訪問(wèn)：http://localhost:8080/webjars/jquery/3.3.1/jquery.js即可。

必須在這幾個(gè)路徑下SpringBoot才會(huì)掃描到！

'classpath:/META-INF/resources/', 'classpath:/resources/','classpath:/static/', 'classpath:/public/' '/'：當(dāng)前項(xiàng)目的根路徑

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