一、说在前面的话
我们之间介绍过SpringBoot自动配置的原理,基本上是如下:
xxxxAutoConfiguration:帮我们给容器中自动配置组件;
xxxxProperties:配置类来封装配置文件的内容;
具体可参考【SpringBoot之自动配置原理解析】
二、静态资源映射规则
1、对哪些目录映射?
classpath:/META-INF/resources/
classpath:/resources/
classpath:/static/
classpath:/public/
/:当前项目的根路径
2、什么意思?
就我们在上面五个目录下放静态资源(比如:a.js等),可以直接访问(http://localhost:8080/a.js),类似于以前web项目的webapp下;放到其他目录下无法被访问。
3、为什么是那几个目录?
3.1、看源码
我们一起来读下源码,这个是SpringBoot自动配置的WebMvcAutoConfiguration.java
类来帮我们干的。
@Override
public 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、分析源码
我们重点分析后半截,前半截后面会介绍。
// staticPathPattern是/**
String staticPathPattern = this.mvcProperties.getStaticPathPattern();
if (!registry.hasMappingForPattern(staticPathPattern)) {
customizeResourceHandlerRegistration(
registry.addResourceHandler(staticPathPattern)
.addResourceLocations(
this.resourceProperties.getStaticLocations())
.setCachePeriod(cachePeriod));
}
this.resourceProperties.getStaticLocations()
========>
ResourceProperties
public 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 {
// 可以看到如下是对上面两个数组进行复制操作到一个新数组上,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);
}
所以上述代码经过我的翻译后成为了如下样子:
registry.addResourceHandler("/**").addResourceLocations(
"classpath:/META-INF/resources/", "classpath:/resources/",
"classpath:/static/", "classpath:/public/", "/")
// 设置缓存时间
.setCachePeriod(cachePeriod));
3.3、一句话概括
WebMvcAutoConfiguration
类自动为我们注册了如下目录为静态资源目录,也就是说直接可访问到资源的目录。
classpath:/META-INF/resources/
classpath:/resources/
classpath:/static/
classpath:/public/
/:当前项目的根路径
优先级从上到下。
所以,如果static里面有个index.html,public下面也有个index.html,则优先会加载static下面的index.html,因为优先级!
4、默认首页
PS:就是直接输入ip:port/项目名称默认进入的页面。
4.1、看源码
WebMvcAutoConfiguration.java
@Bean
public WelcomePageHandlerMapping welcomePageHandlerMapping(
ResourceProperties resourceProperties) {
return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(),
this.mvcProperties.getStaticPathPattern());
}
4.2、分析源码
resourceProperties.getWelcomePage()
========>
public Resource getWelcomePage() {
// 遍历默认静态资源目录后面拼接个index.html的数组
// 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;
}
========>
// 下面这段代码通俗易懂,就是给默认静态资源目录后面拼接个index.html并返回,比如:/static/index.html
private 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;
}
所以上述代码经过我的翻译后成为了如下样子:
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、一句话概括
WebMvcAutoConfiguration
类自动为我们注册了如下文件为默认首页。
classpath:/META-INF/resources/index.html
classpath:/resources/index.html
classpath:/static/index.html
classpath:/public/index.html
/index.html
优先级从上到下。
所以,如果static里面有个index.html,public下面也有个index.html,则优先会加载static下面的index.html,因为优先级!
5、favicon.ico
PS:就是 image.png
这个图标。
5.1、看源码
@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、分析源码
// 首先可以看到的是可以设置是否生效,通过参数spring.mvc.favicon.enabled来配置,若无此参数,则默认是生效的。
@ConditionalOnProperty(value = "spring.mvc.favicon.enabled", matchIfMissing = true)
========》
// 可以看到所有的**/favicon.ico都是在faviconRequestHandler()这个方法里找。
mapping.setUrlMap(Collections.singletonMap("**/favicon.ico", faviconRequestHandler()));
========》
faviconRequestHandler().this.resourceProperties.getFaviconLocations()
// 就是之前的五个静态资源文件夹。
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、一句话概括
只要把favicon.ico放到如下目录下,就会自动生效。
classpath:/META-INF/resources/
classpath:/resources/
classpath:/static/
classpath:/public/
/:当前项目的根路径
6、webjars
6.1、看源码
WebMvcAutoConfiguration
@Override
public 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、分析源码
这次我们来分析前半截。
Integer cachePeriod = this.resourceProperties.getCachePeriod();
if (!registry.hasMappingForPattern("/webjars/**")) {
customizeResourceHandlerRegistration(
registry.addResourceHandler("/webjars/**")
.addResourceLocations(
"classpath:/META-INF/resources/webjars/")
.setCachePeriod(cachePeriod));
}
6.3、一句话概括
所有/webjars/**
都从classpath:/META-INF/resources/webjars/
路径下去找对应的静态资源。
6.4、什么是webjars?
就是以jar包的方式引入静态资源。
官网地址:http://www.webjars.org/。类似于maven仓库。
image.png我们可以做个例子,将jquery引入到项目中
<dependency>
<groupId>org.webjars</groupId>
<artifactId>jquery</artifactId>
<version>3.3.1</version>
</dependency>
看项目依赖
image.png会自动为我们引入jquery,要怎么使用呢?我们上面说过:
所有/webjars/*
都从classpath:/META-INF/resources/webjars/
路径下去找对应的静态资源。
所以我们启动项目,访问:http://localhost:8080/webjars/jquery/3.3.1/jquery.js即可。
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