Adding a Favicon for Blobs and Other Non-HTML Resources

package com.example.cae.favicon;

import com.coremedia.blueprint.cae.handlers.HandlerBase;
import com.coremedia.blueprint.cae.handlers.NavigationSegmentsUriHelper;
import com.coremedia.blueprint.common.contentbeans.CMNavigation;
import com.coremedia.blueprint.common.contentbeans.CMTheme;
import com.coremedia.cap.common.Blob;
import com.coremedia.cap.common.CapBlobRef;
import com.coremedia.cap.common.CapPropertyDescriptor;
import com.coremedia.cap.common.CapPropertyDescriptorType;
import com.coremedia.cap.content.Content;
import com.coremedia.objectserver.web.HandlerHelper;
import com.coremedia.objectserver.web.UserVariantHelper;
import com.coremedia.objectserver.web.cachecontrol.CacheControlStrategy;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.servlet.ModelAndView;

/**
 * Delivers a site's favicon. For example, {@code /service/favicon/corporate} serves the favicon blob of
 * the site's root channel, if set, or else the {@code img/favicon.ico} of the site's theme.
 * A reverse proxy maps {@code /favicon.ico} of each host to this URL.
 */
@Controller
public class SiteFaviconHandler extends HandlerBase {

  private static final String URI_PATTERN = "/service/favicon/{root}";
  private static final String THEME_FAVICON_PATH = "img/favicon.ico";
  private static final String THEME_RESOURCE_BLOB_PROPERTY = "data";

  private final NavigationSegmentsUriHelper navigationSegmentsUriHelper;

  public SiteFaviconHandler(NavigationSegmentsUriHelper navigationSegmentsUriHelper) {
    this.navigationSegmentsUriHelper = navigationSegmentsUriHelper;
  }

  @GetMapping(URI_PATTERN)
  public ModelAndView handleFavicon(@PathVariable("root") String segment,
                                    WebRequest webRequest,
                                    HttpServletRequest request,
                                    HttpServletResponse response) {
    CMNavigation rootNavigation = navigationSegmentsUriHelper.lookupRootSegment(segment);
    if (rootNavigation == null) {
      return HandlerHelper.notFound("Unknown root segment " + segment);
    }

    CapBlobRef blob = getFavicon(rootNavigation, request);
    if (blob == null) {
      return HandlerHelper.notFound("No favicon for " + segment);
    }

    if (webRequest.checkNotModified(blob.getETag())) {
      // expose the model, so that the CacheControlStrategy can compute the TTL of the 304 response
      webRequest.setAttribute(CacheControlStrategy.NOT_MODIFIED_ROOT_MODEL_KEY, blob, WebRequest.SCOPE_REQUEST);
      return null;
    }

    return doCreateModelWithView(true, blob, null, null, response);
  }

  private static CapBlobRef getFavicon(CMNavigation rootNavigation, HttpServletRequest request) {
    // optional override: the favicon of the root channel
    Blob favicon = rootNavigation.getFavicon();
    if (favicon instanceof CapBlobRef blob) {
      return blob;
    }
    // the developer selects a theme variant in the preview, as for HTML pages
    return getThemeFavicon(rootNavigation.getTheme(UserVariantHelper.getUser(request)));
  }

  private static CapBlobRef getThemeFavicon(CMTheme theme) {
    if (theme == null) {
      return null;
    }
    // theme resources are located relative to the folder of the theme document
    Content themeFolder = theme.getContent().getParent();
    Content resource = themeFolder == null ? null : themeFolder.getChild(THEME_FAVICON_PATH);
    if (resource == null || !resource.isDocument()) {
      return null;
    }
    CapPropertyDescriptor descriptor = resource.getType().getDescriptor(THEME_RESOURCE_BLOB_PROPERTY);
    if (descriptor == null || descriptor.getType() != CapPropertyDescriptorType.BLOB) {
      return null;
    }
    return resource.getBlobRef(THEME_RESOURCE_BLOB_PROPERTY);
  }
}

package com.example.cae.favicon;

import com.coremedia.blueprint.base.links.ContentLinkBuilder;
import com.coremedia.blueprint.base.links.UrlPathFormattingHelper;
import com.coremedia.blueprint.cae.handlers.NavigationSegmentsUriHelper;
import com.coremedia.mimetype.MimeTypeService;
import com.coremedia.objectserver.dataviews.DataViewFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import static com.coremedia.blueprint.cae.config.BlueprintHandlersCaeBaseLibConfiguration.configureHandlerBase;

@Configuration(proxyBeanMethods = false)
public class FaviconCaeConfiguration {

  @Bean
  public SiteFaviconHandler siteFaviconHandler(NavigationSegmentsUriHelper navigationSegmentsUriHelper,
                                               MimeTypeService mimeTypeService,
                                               UrlPathFormattingHelper urlPathFormattingHelper,
                                               DataViewFactory dataViewFactory,
                                               ContentLinkBuilder contentLinkBuilder) {
    SiteFaviconHandler handler = new SiteFaviconHandler(navigationSegmentsUriHelper);
    configureHandlerBase(handler, mimeTypeService, urlPathFormattingHelper, dataViewFactory, contentLinkBuilder);
    return handler;
  }
}

server {
    server_name www.example.com;

    location = /favicon.ico {
        proxy_pass http://cae/blueprint/servlet/service/favicon/corporate;
        proxy_set_header Host $http_host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

    # ... other locations of the site
}

http:
  routers:
    cae-live-corporate-favicon:
      # lower priority than any landing page route but higher than the servlet catch-all rule
      priority: 40
      entrypoints:
        - webaccesssecure
        - webaccessinsecure
      rule: Host(`corporate.{{ env "ENVIRONMENT_FQDN"}}`) && Path(`/favicon.ico`)
      service: cae-live
      middlewares:
        - cae-live-corporate-favicon@file

  middlewares:
    cae-live-corporate-favicon:
      replacePath:
        path: "/blueprint/servlet/service/favicon/corporate"