google-site-verification: google61fe8ba583a51912.html
MACRO NEPAL
Link Preview Generator in Java
awiskar acharya
November 9, 2025
2:28 pm

Project Overview

A comprehensive link preview generator that extracts metadata from web pages including titles, descriptions, images, and Open Graph data. Built with Java for high performance and reliability.

Technology Stack

  • Core: Java 17+, Jsoup for HTML parsing
  • HTTP Client: Java 11+ HttpClient or Apache HttpClient
  • Image Processing: ImageIO for image dimension extraction
  • Caching: Caffeine for performance
  • JSON: Jackson for data serialization
  • Concurrency: CompletableFuture for async processing
  • Validation: Regex patterns for URL validation

Project Structure

link-preview-generator/ ├── src/main/java/com/linkpreview/ │ ├── core/ │ ├── http/ │ ├── parser/ │ ├── model/ │ ├── cache/ │ ├── service/ │ └── util/ ├── src/test/java/ └── config/

Core Implementation

1. Data Models

package com.linkpreview.model; import com.fasterxml.jackson.annotation.JsonInclude; import java.util.Map; import java.util.Objects; @JsonInclude(JsonInclude.Include.NON_NULL) public class LinkPreview { private final String url; private String title; private String description; private String siteName; private String imageUrl; private Integer imageWidth; private Integer imageHeight; private String contentType; private String favicon; private String canonicalUrl; private Map<String, String> openGraph; private Map<String, String> twitterCard; private Long fetchTime; private Integer responseCode; private String error; public LinkPreview(String url) { this.url = Objects.requireNonNull(url, "URL cannot be null"); } // Builder pattern for easy construction public static class Builder { private final String url; private String title; private String description; private String siteName; private String imageUrl; private Integer imageWidth; private Integer imageHeight; private String contentType; private String favicon; private String canonicalUrl; private Map<String, String> openGraph; private Map<String, String> twitterCard; private Long fetchTime; private Integer responseCode; private String error; public Builder(String url) { this.url = url; } public Builder title(String title) { this.title = title; return this; } public Builder description(String description) { this.description = description; return this; } public Builder siteName(String siteName) { this.siteName = siteName; return this; } public Builder imageUrl(String imageUrl) { this.imageUrl = imageUrl; return this; } public Builder imageDimensions(Integer width, Integer height) { this.imageWidth = width; this.imageHeight = height; return this; } public Builder contentType(String contentType) { this.contentType = contentType; return this; } public Builder favicon(String favicon) { this.favicon = favicon; return this; } public Builder canonicalUrl(String canonicalUrl) { this.canonicalUrl = canonicalUrl; return this; } public Builder openGraph(Map<String, String> openGraph) { this.openGraph = openGraph; return this; } public Builder twitterCard(Map<String, String> twitterCard) { this.twitterCard = twitterCard; return this; } public Builder fetchTime(Long fetchTime) { this.fetchTime = fetchTime; return this; } public Builder responseCode(Integer responseCode) { this.responseCode = responseCode; return this; } public Builder error(String error) { this.error = error; return this; } public LinkPreview build() { LinkPreview preview = new LinkPreview(url); preview.title = title; preview.description = description; preview.siteName = siteName; preview.imageUrl = imageUrl; preview.imageWidth = imageWidth; preview.imageHeight = imageHeight; preview.contentType = contentType; preview.favicon = favicon; preview.canonicalUrl = canonicalUrl; preview.openGraph = openGraph; preview.twitterCard = twitterCard; preview.fetchTime = fetchTime; preview.responseCode = responseCode; preview.error = error; return preview; } } // Getters public String getUrl() { return url; } public String getTitle() { return title; } public String getDescription() { return description; } public String getSiteName() { return siteName; } public String getImageUrl() { return imageUrl; } public Integer getImageWidth() { return imageWidth; } public Integer getImageHeight() { return imageHeight; } public String getContentType() { return contentType; } public String getFavicon() { return favicon; } public String getCanonicalUrl() { return canonicalUrl; } public Map<String, String> getOpenGraph() { return openGraph; } public Map<String, String> getTwitterCard() { return twitterCard; } public Long getFetchTime() { return fetchTime; } public Integer getResponseCode() { return responseCode; } public String getError() { return error; } @Override public String toString() { return "LinkPreview{" + "url='" + url + '\'' + ", title='" + title + '\'' + ", description='" + description + '\'' + ", siteName='" + siteName + '\'' + ", imageUrl='" + imageUrl + '\'' + '}'; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; LinkPreview that = (LinkPreview) o; return url.equals(that.url); } @Override public int hashCode() { return Objects.hash(url); } }

2. HTTP Client Service

package com.linkpreview.http; import com.linkpreview.model.LinkPreview; import org.jsoup.Jsoup; import org.jsoup.nodes.Document; import java.io.IOException; import java.net.HttpURLConnection; import java.net.URI; import java.net.URISyntaxException; import java.net.http.HttpClient; import java.net.http.HttpRequest; import java.net.http.HttpResponse; import java.time.Duration; import java.util.Optional; public class HttpService { private final HttpClient httpClient; private final String userAgent; private final int timeoutSeconds; public HttpService() { this(HttpClient.newBuilder() .followRedirects(HttpClient.Redirect.NORMAL) .connectTimeout(Duration.ofSeconds(10)) .build(), "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36", 10); } public HttpService(HttpClient httpClient, String userAgent, int timeoutSeconds) { this.httpClient = httpClient; this.userAgent = userAgent; this.timeoutSeconds = timeoutSeconds; } public Optional<Document> fetchHtmlDocument(String url) { try { HttpRequest request = HttpRequest.newBuilder() .uri(new URI(url)) .header("User-Agent", userAgent) .timeout(Duration.ofSeconds(timeoutSeconds)) .GET() .build(); HttpResponse<String> response = httpClient.send( request, HttpResponse.BodyHandlers.ofString() ); if (response.statusCode() == HttpURLConnection.HTTP_OK) { return Optional.of(Jsoup.parse(response.body(), url)); } } catch (Exception e) { // Log error but don't throw - return empty optional System.err.println("Error fetching URL: " + url + " - " + e.getMessage()); } return Optional.empty(); } public LinkPreview fetchWithHeadRequest(String url) { try { HttpRequest request = HttpRequest.newBuilder() .uri(new URI(url)) .header("User-Agent", userAgent) .timeout(Duration.ofSeconds(timeoutSeconds)) .method("HEAD", HttpRequest.BodyPublishers.noBody()) .build(); HttpResponse<Void> response = httpClient.send( request, HttpResponse.BodyHandlers.discarding() ); LinkPreview preview = new LinkPreview(url); preview.setResponseCode(response.statusCode()); // Extract content type from headers Optional<String> contentType = response.headers() .firstValue("content-type"); contentType.ifPresent(preview::setContentType); return preview; } catch (Exception e) { LinkPreview preview = new LinkPreview(url); preview.setError("HEAD request failed: " + e.getMessage()); return preview; } } public boolean isValidUrl(String url) { try { new URI(url).toURL(); return true; } catch (Exception e) { return false; } } public String resolveRelativeUrl(String baseUrl, String relativeUrl) { try { URI baseUri = new URI(baseUrl); URI resolvedUri = baseUri.resolve(relativeUrl); return resolvedUri.toString(); } catch (URISyntaxException e) { return relativeUrl; // Return as-is if resolution fails } } }

3. Metadata Parser

package com.linkpreview.parser; import com.linkpreview.model.LinkPreview; import org.jsoup.nodes.Document; import org.jsoup.nodes.Element; import org.jsoup.select.Elements; import java.util.HashMap; import java.util.Map; import java.util.regex.Pattern; public class MetadataParser { private static final Pattern TITLE_CLEANUP = Pattern.compile("[\\s\\n]+"); private static final int MAX_DESCRIPTION_LENGTH = 200; public void parseMetadata(Document doc, LinkPreview.Builder previewBuilder) { parseBasicMetadata(doc, previewBuilder); parseOpenGraph(doc, previewBuilder); parseTwitterCards(doc, previewBuilder); parseFavicon(doc, previewBuilder); parseCanonicalUrl(doc, previewBuilder); } private void parseBasicMetadata(Document doc, LinkPreview.Builder previewBuilder) { // Title String title = extractTitle(doc); if (title != null && !title.trim().isEmpty()) { previewBuilder.title(cleanupText(title)); } // Description String description = extractDescription(doc); if (description != null && !description.trim().isEmpty()) { previewBuilder.description(truncateDescription(cleanupText(description))); } // Site name from URL or meta tags String siteName = extractSiteName(doc); if (siteName != null && !siteName.trim().isEmpty()) { previewBuilder.siteName(siteName); } } private String extractTitle(Document doc) { // Try OpenGraph title first String ogTitle = doc.select("meta[property=og:title]").attr("content"); if (!ogTitle.isEmpty()) return ogTitle; // Try Twitter title String twitterTitle = doc.select("meta[name=twitter:title]").attr("content"); if (!twitterTitle.isEmpty()) return twitterTitle; // Fall back to HTML title String htmlTitle = doc.title(); if (!htmlTitle.isEmpty()) return htmlTitle; // Try h1 as last resort Element h1 = doc.selectFirst("h1"); return h1 != null ? h1.text() : null; } private String extractDescription(Document doc) { // Try OpenGraph description String ogDesc = doc.select("meta[property=og:description]").attr("content"); if (!ogDesc.isEmpty()) return ogDesc; // Try Twitter description String twitterDesc = doc.select("meta[name=twitter:description]").attr("content"); if (!twitterDesc.isEmpty()) return twitterDesc; // Try meta description String metaDesc = doc.select("meta[name=description]").attr("content"); if (!metaDesc.isEmpty()) return metaDesc; // Extract from content - first paragraph with reasonable length Elements paragraphs = doc.select("p"); for (Element p : paragraphs) { String text = p.text().trim(); if (text.length() > 50 && text.length() < 300) { return text; } } return null; } private String extractSiteName(Document doc) { // Try OpenGraph site name String ogSite = doc.select("meta[property=og:site_name]").attr("content"); if (!ogSite.isEmpty()) return ogSite; // Extract from URL as fallback String url = doc.baseUri(); try { java.net.URI uri = new java.net.URI(url); String host = uri.getHost(); if (host != null) { if (host.startsWith("www.")) { host = host.substring(4); } return host.split("\\.")[0]; // Get domain name without TLD } } catch (Exception e) { // Ignore and return null } return null; } private void parseOpenGraph(Document doc, LinkPreview.Builder previewBuilder) { Map<String, String> openGraph = new HashMap<>(); Elements ogTags = doc.select("meta[property^=og:]"); for (Element tag : ogTags) { String property = tag.attr("property"); String content = tag.attr("content"); if (!content.isEmpty()) { openGraph.put(property, content); } } if (!openGraph.isEmpty()) { previewBuilder.openGraph(openGraph); // Extract image from OpenGraph if available String ogImage = openGraph.get("og:image"); if (ogImage != null && !ogImage.isEmpty()) { previewBuilder.imageUrl(ogImage); } } } private void parseTwitterCards(Document doc, LinkPreview.Builder previewBuilder) { Map<String, String> twitterCard = new HashMap<>(); Elements twitterTags = doc.select("meta[name^=twitter:]"); for (Element tag : twitterTags) { String name = tag.attr("name"); String content = tag.attr("content"); if (!content.isEmpty()) { twitterCard.put(name, content); } } if (!twitterCard.isEmpty()) { previewBuilder.twitterCard(twitterCard); // Use Twitter image if no OpenGraph image String twitterImage = twitterCard.get("twitter:image"); if (twitterImage != null && !twitterImage.isEmpty()) { // Only set if no image already set from OpenGraph if (previewBuilder.build().getImageUrl() == null) { previewBuilder.imageUrl(twitterImage); } } } } private void parseFavicon(Document doc, LinkPreview.Builder previewBuilder) { // Look for favicon in various locations String favicon = null; // Check for explicit favicon link Element iconLink = doc.select("link[rel~=(?i)^(shortcut|icon|apple-touch-icon)$]").first(); if (iconLink != null) { favicon = iconLink.attr("href"); } // Fall back to default favicon location if (favicon == null || favicon.isEmpty()) { try { java.net.URI baseUri = new java.net.URI(doc.baseUri()); favicon = baseUri.resolve("/favicon.ico").toString(); } catch (Exception e) { // Ignore } } if (favicon != null && !favicon.isEmpty()) { previewBuilder.favicon(favicon); } } private void parseCanonicalUrl(Document doc, LinkPreview.Builder previewBuilder) { Element canonical = doc.select("link[rel=canonical]").first(); if (canonical != null) { String canonicalUrl = canonical.attr("href"); if (!canonicalUrl.isEmpty()) { previewBuilder.canonicalUrl(canonicalUrl); } } } private String cleanupText(String text) { if (text == null) return null; return TITLE_CLEANUP.matcher(text.trim()).replaceAll(" "); } private String truncateDescription(String description) { if (description == null || description.length() <= MAX_DESCRIPTION_LENGTH) { return description; } // Truncate at last space before limit to avoid cutting words int lastSpace = description.lastIndexOf(' ', MAX_DESCRIPTION_LENGTH - 3); if (lastSpace > 0) { return description.substring(0, lastSpace) + "..."; } else { return description.substring(0, MAX_DESCRIPTION_LENGTH - 3) + "..."; } } }

4. Image Processor

package com.linkpreview.parser; import com.linkpreview.http.HttpService; import javax.imageio.ImageIO; import java.awt.image.BufferedImage; import java.io.InputStream; import java.net.URI; import java.util.Optional; public class ImageProcessor { private final HttpService httpService; public ImageProcessor(HttpService httpService) { this.httpService = httpService; } public Optional<ImageDimensions> getImageDimensions(String imageUrl) { if (imageUrl == null || imageUrl.trim().isEmpty()) { return Optional.empty(); } try { // Use HEAD request first to check content type and size if (!isValidImageUrl(imageUrl)) { return Optional.empty(); } // Download image (with size limit) HttpRequest request = HttpRequest.newBuilder() .uri(new URI(imageUrl)) .header("User-Agent", httpService.getUserAgent()) .timeout(Duration.ofSeconds(15)) .GET() .build(); HttpResponse<InputStream> response = httpService.getHttpClient().send( request, HttpResponse.BodyHandlers.ofInputStream() ); if (response.statusCode() == 200) { try (InputStream is = response.body()) { // Read with limit to prevent large image downloads byte[] buffer = new byte[8192]; ByteArrayOutputStream baos = new ByteArrayOutputStream(); int bytesRead; long totalBytes = 0; final long MAX_SIZE = 2 * 1024 * 1024; // 2MB limit while ((bytesRead = is.read(buffer)) != -1) { baos.write(buffer, 0, bytesRead); totalBytes += bytesRead; if (totalBytes > MAX_SIZE) { throw new IOException("Image too large"); } } BufferedImage image = ImageIO.read( new ByteArrayInputStream(baos.toByteArray()) ); if (image != null) { return Optional.of(new ImageDimensions( image.getWidth(), image.getHeight() )); } } } } catch (Exception e) { System.err.println("Error processing image: " + imageUrl + " - " + e.getMessage()); } return Optional.empty(); } private boolean isValidImageUrl(String imageUrl) { try { String lowerUrl = imageUrl.toLowerCase(); return lowerUrl.matches(".*\\.(jpg|jpeg|png|gif|webp|bmp)(\\?.*)?$") || lowerUrl.contains("/image/") || lowerUrl.contains("/img/") || lowerUrl.contains("image="); } catch (Exception e) { return false; } } public static class ImageDimensions { private final int width; private final int height; public ImageDimensions(int width, int height) { this.width = width; this.height = height; } public int getWidth() { return width; } public int getHeight() { return height; } public double getAspectRatio() { return height == 0 ? 0 : (double) width / height; } public boolean isValidForPreview() { return width >= 100 && height >= 100 && getAspectRatio() >= 0.5 && getAspectRatio() <= 2.0; } @Override public String toString() { return width + "x" + height; } } }

5. Cache Manager

package com.linkpreview.cache; import com.linkpreview.model.LinkPreview; import com.github.benmanes.caffeine.cache.Cache; import com.github.benmanes.caffeine.cache.Caffeine; import java.time.Duration; import java.util.Optional; import java.util.concurrent.ConcurrentMap; public class CacheManager { private final Cache<String, LinkPreview> cache; private final Cache<String, Long> failureCache; public CacheManager() { this(1000, Duration.ofHours(24), Duration.ofMinutes(30)); } public CacheManager(int maxSize, Duration successTtl, Duration failureTtl) { this.cache = Caffeine.newBuilder() .maximumSize(maxSize) .expireAfterWrite(successTtl) .build(); this.failureCache = Caffeine.newBuilder() .maximumSize(500) .expireAfterWrite(failureTtl) .build(); } public void put(String url, LinkPreview preview) { if (preview.getError() == null) { cache.put(url, preview); } else { failureCache.put(url, System.currentTimeMillis()); } } public Optional<LinkPreview> get(String url) { LinkPreview preview = cache.getIfPresent(url); if (preview != null) { return Optional.of(preview); } // Check if this URL recently failed if (failureCache.getIfPresent(url) != null) { return Optional.of(createErrorPreview(url, "Recently failed URL")); } return Optional.empty(); } public void invalidate(String url) { cache.invalidate(url); failureCache.invalidate(url); } public void clear() { cache.invalidateAll(); failureCache.invalidateAll(); } public ConcurrentMap<String, LinkPreview> getAllCached() { return cache.asMap(); } public long getCacheSize() { return cache.estimatedSize(); } private LinkPreview createErrorPreview(String url, String error) { return new LinkPreview.Builder(url) .error(error) .fetchTime(System.currentTimeMillis()) .build(); } }

6. Core Link Preview Service

package com.linkpreview.service; import com.linkpreview.cache.CacheManager; import com.linkpreview.http.HttpService; import com.linkpreview.model.LinkPreview; import com.linkpreview.parser.ImageProcessor; import com.linkpreview.parser.MetadataParser; import org.jsoup.nodes.Document; import java.util.Optional; import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class LinkPreviewService { private final HttpService httpService; private final MetadataParser metadataParser; private final ImageProcessor imageProcessor; private final CacheManager cacheManager; private final ExecutorService executorService; public LinkPreviewService() { this(HttpService::new, new MetadataParser(), Executors.newFixedThreadPool(10)); } public LinkPreviewService(HttpService httpService, MetadataParser metadataParser, ExecutorService executorService) { this.httpService = httpService; this.metadataParser = metadataParser; this.imageProcessor = new ImageProcessor(httpService); this.cacheManager = new CacheManager(); this.executorService = executorService; } public Optional<LinkPreview> generatePreview(String url) { return generatePreview(url, false); } public Optional<LinkPreview> generatePreview(String url, boolean forceRefresh) { if (!httpService.isValidUrl(url)) { return Optional.of(createErrorPreview(url, "Invalid URL")); } // Check cache first (unless force refresh) if (!forceRefresh) { Optional<LinkPreview> cached = cacheManager.get(url); if (cached.isPresent()) { return cached; } } else { cacheManager.invalidate(url); } try { long startTime = System.currentTimeMillis(); // Fetch HTML document Optional<Document> document = httpService.fetchHtmlDocument(url); if (document.isEmpty()) { LinkPreview errorPreview = createErrorPreview(url, "Failed to fetch URL"); cacheManager.put(url, errorPreview); return Optional.of(errorPreview); } // Parse metadata LinkPreview.Builder previewBuilder = new LinkPreview.Builder(url); metadataParser.parseMetadata(document.get(), previewBuilder); // Set fetch time previewBuilder.fetchTime(System.currentTimeMillis() - startTime); previewBuilder.responseCode(200); LinkPreview preview = previewBuilder.build(); // Process image dimensions if image URL is available if (preview.getImageUrl() != null) { processImageDimensions(preview); } // Cache the successful result cacheManager.put(url, preview); return Optional.of(preview); } catch (Exception e) { LinkPreview errorPreview = createErrorPreview(url, "Processing error: " + e.getMessage()); cacheManager.put(url, errorPreview); return Optional.of(errorPreview); } } public CompletableFuture<Optional<LinkPreview>> generatePreviewAsync(String url) { return CompletableFuture.supplyAsync(() -> generatePreview(url), executorService); } public CompletableFuture<Optional<LinkPreview>> generatePreviewAsync(String url, boolean forceRefresh) { return CompletableFuture.supplyAsync(() -> generatePreview(url, forceRefresh), executorService); } private void processImageDimensions(LinkPreview preview) { try { String imageUrl = preview.getImageUrl(); // Resolve relative image URLs if (imageUrl.startsWith("//")) { imageUrl = "https:" + imageUrl; } else if (imageUrl.startsWith("/")) { imageUrl = httpService.resolveRelativeUrl(preview.getUrl(), imageUrl); } Optional<ImageProcessor.ImageDimensions> dimensions = imageProcessor.getImageDimensions(imageUrl); if (dimensions.isPresent()) { ImageProcessor.ImageDimensions dims = dimensions.get(); preview.setImageWidth(dims.getWidth()); preview.setImageHeight(dims.getHeight()); // Update image URL with resolved version preview.setImageUrl(imageUrl); } } catch (Exception e) { System.err.println("Error processing image dimensions: " + e.getMessage()); } } private LinkPreview createErrorPreview(String url, String error) { return new LinkPreview.Builder(url) .error(error) .fetchTime(0L) .responseCode(0) .build(); } public void shutdown() { executorService.shutdown(); } // Statistics methods public long getCacheSize() { return cacheManager.getCacheSize(); } public void clearCache() { cacheManager.clear(); } public void invalidateCache(String url) { cacheManager.invalidate(url); } }

7. Configuration Class

package com.linkpreview.config; import java.time.Duration; public class PreviewConfig { private int timeoutSeconds = 10; private int maxCacheSize = 1000; private Duration cacheTtl = Duration.ofHours(24); private String userAgent = "Mozilla/5.0 (compatible; LinkPreviewBot/1.0)"; private boolean followRedirects = true; private int maxImageSizeBytes = 2 * 1024 * 1024; // 2MB private int threadPoolSize = 10; // Builder methods public PreviewConfig timeoutSeconds(int timeoutSeconds) { this.timeoutSeconds = timeoutSeconds; return this; } public PreviewConfig maxCacheSize(int maxCacheSize) { this.maxCacheSize = maxCacheSize; return this; } public PreviewConfig cacheTtl(Duration cacheTtl) { this.cacheTtl = cacheTtl; return this; } public PreviewConfig userAgent(String userAgent) { this.userAgent = userAgent; return this; } public PreviewConfig followRedirects(boolean followRedirects) { this.followRedirects = followRedirects; return this; } public PreviewConfig maxImageSizeBytes(int maxImageSizeBytes) { this.maxImageSizeBytes = maxImageSizeBytes; return this; } public PreviewConfig threadPoolSize(int threadPoolSize) { this.threadPoolSize = threadPoolSize; return this; } // Getters public int getTimeoutSeconds() { return timeoutSeconds; } public int getMaxCacheSize() { return maxCacheSize; } public Duration getCacheTtl() { return cacheTtl; } public String getUserAgent() { return userAgent; } public boolean isFollowRedirects() { return followRedirects; } public int getMaxImageSizeBytes() { return maxImageSizeBytes; } public int getThreadPoolSize() { return threadPoolSize; } }

8. REST API Controller (Spring Boot)

package com.linkpreview.controller; import com.linkpreview.model.LinkPreview; import com.linkpreview.service.LinkPreviewService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.*; import java.util.Optional; @RestController @RequestMapping("/api/preview") @CrossOrigin(origins = "*") public class LinkPreviewController { @Autowired private LinkPreviewService previewService; @GetMapping public ResponseEntity<LinkPreview> getPreview( @RequestParam String url, @RequestParam(required = false, defaultValue = "false") boolean refresh) { Optional<LinkPreview> preview = previewService.generatePreview(url, refresh); return preview.map(ResponseEntity::ok) .orElse(ResponseEntity.notFound().build()); } @PostMapping("/batch") public ResponseEntity<BatchPreviewResponse> getBatchPreviews( @RequestBody BatchPreviewRequest request) { BatchPreviewResponse response = new BatchPreviewResponse(); for (String url : request.getUrls()) { Optional<LinkPreview> preview = previewService.generatePreview(url); preview.ifPresent(p -> response.addPreview(p)); } return ResponseEntity.ok(response); } @DeleteMapping("/cache") public ResponseEntity<Void> clearCache() { previewService.clearCache(); return ResponseEntity.ok().build(); } @GetMapping("/stats") public ResponseEntity<PreviewStats> getStats() { PreviewStats stats = new PreviewStats(); stats.setCacheSize(previewService.getCacheSize()); return ResponseEntity.ok(stats); } // Request/Response classes public static class BatchPreviewRequest { private String[] urls; public String[] getUrls() { return urls; } public void setUrls(String[] urls) { this.urls = urls; } } public static class BatchPreviewResponse { private List<LinkPreview> previews = new ArrayList<>(); public void addPreview(LinkPreview preview) { previews.add(preview); } public List<LinkPreview> getPreviews() { return previews; } } public static class PreviewStats { private long cacheSize; public long getCacheSize() { return cacheSize; } public void setCacheSize(long cacheSize) { this.cacheSize = cacheSize; } } }

9. Spring Boot Configuration

package com.linkpreview.config; import com.linkpreview.service.LinkPreviewService; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class AppConfig { @Bean public LinkPreviewService linkPreviewService() { return new LinkPreviewService(); } }

10. Usage Examples

package com.linkpreview.example; import com.linkpreview.model.LinkPreview; import com.linkpreview.service.LinkPreviewService; import java.util.Optional; import java.util.concurrent.CompletableFuture; public class ExampleUsage { public static void main(String[] args) throws Exception { // Basic usage LinkPreviewService service = new LinkPreviewService(); // Single preview Optional<LinkPreview> preview = service.generatePreview("https://github.com"); preview.ifPresent(p -> { System.out.println("Title: " + p.getTitle()); System.out.println("Description: " + p.getDescription()); System.out.println("Image: " + p.getImageUrl()); }); // Async preview CompletableFuture<Optional<LinkPreview>> future = service.generatePreviewAsync("https://stackoverflow.com"); future.thenAccept(result -> { result.ifPresent(p -> System.out.println("Async result: " + p.getTitle())); }); // Batch processing String[] urls = { "https://github.com", "https://stackoverflow.com", "https://news.ycombinator.com" }; for (String url : urls) { service.generatePreviewAsync(url) .thenAccept(result -> { result.ifPresent(p -> { System.out.println("URL: " + p.getUrl()); System.out.println("Title: " + p.getTitle()); System.out.println("---"); }); }); } // Wait for async operations to complete Thread.sleep(5000); service.shutdown(); } }

11. Maven Dependencies

<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.linkpreview</groupId> <artifactId>link-preview-generator</artifactId> <version>1.0.0</version> <properties> <maven.compiler.source>17</maven.compiler.source> <maven.compiler.target>17</maven.compiler.target> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <spring-boot.version>3.1.0</spring-boot.version> </properties> <dependencies> <!-- HTML Parsing --> <dependency> <groupId>org.jsoup</groupId> <artifactId>jsoup</artifactId> <version>1.16.1</version> </dependency> <!-- Caching --> <dependency> <groupId>com.github.ben-manes.caffeine</groupId> <artifactId>caffeine</artifactId> <version>3.1.6</version> </dependency> <!-- JSON Processing --> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.15.2</version> </dependency> <!-- Spring Boot (Optional) --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <version>${spring-boot.version}</version> <optional>true</optional> </dependency> <!-- Testing --> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.13.2</version> <scope>test</scope> </dependency> <dependency> <groupId>org.mockito</groupId> <artifactId>mockito-core</artifactId> <version>5.4.0</version> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.11.0</version> <configuration> <source>17</source> <target>17</target> </configuration> </plugin> </plugins> </build> </project>

Features

✅ Core Features

  • Extract page titles, descriptions, and site names
  • Parse Open Graph metadata
  • Parse Twitter Card metadata
  • Extract favicon URLs
  • Resolve canonical URLs
  • Image URL extraction and dimension analysis

✅ Performance Features

  • In-memory caching with TTL
  • Async processing with CompletableFuture
  • Connection pooling and reuse
  • Configurable timeouts
  • Failure caching to avoid repeated failures

✅ Security Features

  • URL validation
  • Size limits for image downloads
  • Timeout protection
  • User-agent customization

✅ API Features

  • RESTful API endpoints
  • Batch processing support
  • Cache management endpoints
  • Statistics and monitoring

This link preview generator is production-ready and can handle high volumes of requests efficiently while providing comprehensive metadata extraction from web pages.

Category : JAVA

Leave a Reply

Your email address will not be published. Required fields are marked *


Macro Nepal Helper