General: Cache course icons and profile pictures to improve performance

src/main/java/de/tum/cit/aet/artemis/core/config/PublicResourcesConfiguration.java

@@ -10,6 +10,7 @@
 
 import jakarta.validation.constraints.NotNull;
 
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Profile;
 import org.springframework.http.CacheControl;
@@ -32,6 +33,9 @@ public PublicResourcesConfiguration(JHipsterProperties jHipsterProperties) {
         this.jHipsterProperties = jHipsterProperties;
     }
 
+    @Value("${artemis.file-upload-path}")
+    private String fileUploadPath;
+
     @Override
     public void addResourceHandlers(@NotNull ResourceHandlerRegistry registry) {
         // Enable static resource serving in general from "/public" from both classpath and hosts filesystem
@@ -46,6 +50,16 @@ public void addResourceHandlers(@NotNull ResourceHandlerRegistry registry) {
 
         addResourceHandlerForPath(registry, "images", "about").setCacheControl(defaultCacheControl);
         addResourceHandlerForPath(registry, "emoji").setCacheControl(defaultCacheControl);
+
+        // Add caching for course icons, user profile pictures, and drag and drop quiz pictures
+        // Add resource handlers for dynamic image paths based on fileUploadPath
+        // TODO: those paths have to be the same as in FilePathService, ideally we reuse the constants and define them only once
+        registry.addResourceHandler("/images/course/icons/**").addResourceLocations("file:" + fileUploadPath + "/images/course/icons/").setCacheControl(defaultCacheControl);
+
+        registry.addResourceHandler("/images/user/profile-pictures/**").addResourceLocations("file:" + fileUploadPath + "/images/user/profile-pictures/")
+                .setCacheControl(defaultCacheControl);
+
+        registry.addResourceHandler("/images/drag-and-drop/**").addResourceLocations("file:" + fileUploadPath + "/images/drag-and-drop/").setCacheControl(defaultCacheControl);
     }
 
     /**

src/main/java/de/tum/cit/aet/artemis/core/web/FileResource.java

@@ -12,6 +12,7 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.Set;
+import java.util.concurrent.TimeUnit;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -646,7 +647,8 @@ private ResponseEntity<byte[]> responseEntityForFilePath(Path filePath) {
             if (file == null) {
                 return ResponseEntity.notFound().build();
             }
-            return ResponseEntity.ok(file);
+            return ResponseEntity.ok().cacheControl(CacheControl.maxAge(30, TimeUnit.DAYS)) // Cache for 30 days;
+                    .contentType(getMediaTypeFromFilename(filePath.getFileName().toString())).body(file);
         }
         catch (IOException e) {
             log.error("Failed to return requested file with path {}", filePath, e);

src/main/webapp/app/overview/course-conversations/layout/conversation-messages/conversation-messages.component.ts

@@ -136,6 +136,7 @@ export class ConversationMessagesComponent implements OnInit, AfterViewInit, OnD
             this.createEmptyPost();
         }
     }
+
     private subscribeToMetis() {
         this.metisService.posts.pipe(takeUntil(this.ngUnsubscribe)).subscribe((posts: Post[]) => {
             this.setPosts(posts);

src/main/webapp/app/shared/metis/metis-conversation.service.ts

@@ -116,7 +116,7 @@ export class MetisConversationService implements OnDestroy {
 
     public setActiveConversation(conversationIdentifier: ConversationDTO | number | undefined) {
         this.updateLastReadDateAndNumberOfUnreadMessages();
-        let cachedConversation = undefined;
+        let cachedConversation: ConversationDTO | undefined = undefined;
         if (conversationIdentifier) {
             const parameterJustId = typeof conversationIdentifier === 'number';
             cachedConversation = this.conversationsOfUser.find(