SpringBoot中静态资源映射处理

简介: SpringBoot中静态资源映射处理

上一篇博文说明了SpringBoot对WebJars的支持,那么项目中还有其他静态资源文件,如自定义CSS、JS、image等,SpringBoot同样提供了映射支持。


【1】静态资源文件映射规则


同样查看WebMvcAutoConfiguration源码如下:

@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
  if (!this.resourceProperties.isAddMappings()) {
    logger.debug("Default resource handling disabled");
    return;
  }
  //对webjars做映射处理
  Integer cachePeriod = this.resourceProperties.getCachePeriod();
  if (!registry.hasMappingForPattern("/webjars/**")) {
    customizeResourceHandlerRegistration(
        registry.addResourceHandler("/webjars/**")
            .addResourceLocations(
                "classpath:/META-INF/resources/webjars/")
        .setCachePeriod(cachePeriod));
  }
  // 对静态资源文件映射支持
  String staticPathPattern = this.mvcProperties.getStaticPathPattern();
  if (!registry.hasMappingForPattern(staticPathPattern)) {
    customizeResourceHandlerRegistration(
        registry.addResourceHandler(staticPathPattern)
            .addResourceLocations(
                this.resourceProperties.getStaticLocations())
        .setCachePeriod(cachePeriod));
  }
}
@Override
public void addResourceHandlers(ResourceHandlerRegistry registry) {
registry.addResourceHandler("/upload/**").addResourceLocations("file:"+"D://javasoftinstall/upload/");
registry.addResourceHandler("/**")
    .addResourceLocations("classpath:/resources/")
    .addResourceLocations("classpath:/static/")
super.addResourceHandlers(registry);
}


这里可以看到对静态资源处理的具体支持代码如下:

String staticPathPattern = this.mvcProperties.getStaticPathPattern();
  if (!registry.hasMappingForPattern(staticPathPattern)) {
    customizeResourceHandlerRegistration(
        registry.addResourceHandler(staticPathPattern)
            .addResourceLocations(
                this.resourceProperties.getStaticLocations())
        .setCachePeriod(cachePeriod));
  }


第一步拿到staticPathPattern;

/**
 * Path pattern used for static resources.
 */
private String staticPathPattern = "/**";

第二步,如果资源请求没有对应映射,就添加资源处理器及资源找寻位置并设置缓存

if (!registry.hasMappingForPattern(staticPathPattern)) {
    customizeResourceHandlerRegistration(
        registry.addResourceHandler(staticPathPattern)
            .addResourceLocations(
                this.resourceProperties.getStaticLocations())
        .setCachePeriod(cachePeriod));
  }


其中 staticLocations在ResourceProperties类中,源码如下:

/**
 * Properties used to configure resource handling.
 */
@ConfigurationProperties(prefix = "spring.resources", ignoreUnknownFields = false)
public class ResourceProperties implements ResourceLoaderAware {
  private static final String[] SERVLET_RESOURCE_LOCATIONS = { "/" };
//静态资源映射路径
  private static final String[] CLASSPATH_RESOURCE_LOCATIONS = {
      "classpath:/META-INF/resources/", "classpath:/resources/",
      "classpath:/static/", "classpath:/public/" };
  private static final String[] RESOURCE_LOCATIONS;
  static {
    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);
  }
  /**
   * Locations of static resources. Defaults to classpath:[/META-INF/resources/,
   * /resources/, /static/, /public/] plus context:/ (the root of the servlet context).
   */
  private String[] staticLocations = RESOURCE_LOCATIONS;

即:"/**" 访问当前项目的任何资源,只要没有匹配的处理映射,则都去静态资源的文件夹找映射

"classpath:/META‐INF/resources/",
"classpath:/resources/",
"classpath:/static/",
"classpath:/public/"
"/":当前项目的根路径


如下图,访问static/asserts/img/bootstrap-solid.svg:


20180613142325845.jpg


URL : http://localhost:8083/asserts/img/bootstrap-solid.svg;


这里注意URL上面不要添加静态资源文件夹(路径)的名字,如static、public等等。


【2】默认欢迎页的映射

代码如下:

    @Bean
    public WelcomePageHandlerMapping welcomePageHandlerMapping(
        ResourceProperties resourceProperties) {
      return new WelcomePageHandlerMapping(resourceProperties.getWelcomePage(),
          this.mvcProperties.getStaticPathPattern());
    }

注册了WelcomePageHandlerMappingBean来处理项目的默认欢迎页面,构造器有两个参数,第一个是项目中存在的欢迎页资源,第二个是静态资源路径映射规则。


① 获取欢迎页资源

其中跟踪resourceProperties.getWelcomePage()源码:

  public Resource getWelcomePage() {
    for (String location : getStaticWelcomePageLocations()) {
      Resource resource = this.resourceLoader.getResource(location);
      try {
        if (resource.exists()) {
          resource.getURL();
          return resource;
        }
      }
      catch (Exception ex) {
        // Ignore
      }
    }
    return null;
  }



即找到存在的欢迎页的资源,继续跟getStaticWelcomePageLocations()源码:

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;
  }


即 欢迎页的位置为第【1】部分中静态资源文件路径下的index.html。

如下所示:

"classpath:/META‐INF/resources/index.html",
"classpath:/resources/index.html",
"classpath:/static/index.html",
"classpath:/public/index.html"
"/":/index.html


② 静态路径映射规则

  /**
   * Path pattern used for static resources.
   */
  private String staticPathPattern = "/**";

③ WelcomePageHandlerMapping类

static final class WelcomePageHandlerMapping extends AbstractUrlHandlerMapping {
    private static final Log logger = LogFactory
        .getLog(WelcomePageHandlerMapping.class);
    private WelcomePageHandlerMapping(Resource welcomePage,
        String staticPathPattern) {
      if (welcomePage != null && "/**".equals(staticPathPattern)) {
        logger.info("Adding welcome page: " + welcomePage);
        ParameterizableViewController controller = new ParameterizableViewController();
        controller.setViewName("forward:index.html");
        setRootHandler(controller);
        setOrder(0);
      }
    }
    @Override
    public Object getHandlerInternal(HttpServletRequest request) throws Exception {
      for (MediaType mediaType : getAcceptedMediaTypes(request)) {
        if (mediaType.includes(MediaType.TEXT_HTML)) {
          return super.getHandlerInternal(request);
        }
      }
      return null;
    }
    private List<MediaType> getAcceptedMediaTypes(HttpServletRequest request) {
      String acceptHeader = request.getHeader(HttpHeaders.ACCEPT);
      return MediaType.parseMediaTypes(
          StringUtils.hasText(acceptHeader) ? acceptHeader : "*/*");
    }
  }

总结:项目访问时,请求如http://localhost:8083/,则SpringBoot会从静态资源文件路径下找index.html,如果存在一个这样的资源,就转发请求到该页面。


【3】项目浏览器图标的映射

SpringBoot同样对项目浏览器图标请求映射做了默认配置。浏览器图片即项目访问时,浏览器页面上呈现的图标,如CSDN图标如下


代码如下:

    @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;
      }
    }

跟踪源码this.resourceProperties.getFaviconLocations()如下:

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);
  }


即在静态资源文件下找所有的favicon.ico !

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