improve exception handling

src/main/java/internal/hw/crawler/Main.java

@@ -3,8 +3,12 @@ package internal.hw.crawler;
 import internal.hw.crawler.commands.*;
 import internal.hw.crawler.repositories.ArticleRepository;
 import internal.hw.crawler.views.ConsoleView;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class Main {
+    private static final Logger log = LoggerFactory.getLogger(Main.class);
+
     public static void main(String[] args) {
         ConsoleView view = new ConsoleView();
         MainController controller = new MainController(view);
@@ -27,6 +31,7 @@ public class Main {
                 }
                 controller.handleInput(line);
             } catch (Exception e) {
+                log.error("Unhandled exception in REPL loop", e);
                 view.printError("Unexpected error: " + e.getMessage());
             }
         }

src/main/java/internal/hw/crawler/MainController.java

@@ -2,7 +2,10 @@ package internal.hw.crawler;
 
 import internal.hw.crawler.commands.Command;
 import internal.hw.crawler.commands.CommandArg;
+import internal.hw.crawler.strategies.crawl.CrawlerException;
 import internal.hw.crawler.views.ConsoleView;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.Collections;
 import java.util.HashMap;
@@ -10,6 +13,7 @@ import java.util.List;
 import java.util.Map;
 
 public class MainController {
+    private static final Logger log = LoggerFactory.getLogger(MainController.class);
     private final Map<String, Command> commands = new HashMap<>();
     private final ConsoleView view;
 
@@ -45,8 +49,12 @@ public class MainController {
 
         try {
             command.execute(args);
+        } catch (CrawlerException e) {
+            log.warn("Crawler error in command '{}'", cmdName, e);
+            view.printError(e.getMessage());
         } catch (Exception e) {
-            view.printError("Command failed: " + e.getMessage());
+            log.error("Unexpected error in command '{}'", cmdName, e);
+            view.printError("Internal error: " + e.getMessage());
         }
     }
 

src/main/java/internal/hw/crawler/commands/CrawlCommand.java

@@ -5,15 +5,22 @@ import internal.hw.crawler.repositories.ArticleRepository;
 import internal.hw.crawler.strategies.crawl.CrawlStrategy;
 import internal.hw.crawler.strategies.crawl.CrawlStrategyFactory;
 import internal.hw.crawler.strategies.crawl.CrawlUtils;
+import internal.hw.crawler.strategies.crawl.CrawlNetworkException;
+import internal.hw.crawler.strategies.crawl.CrawlParseException;
+import internal.hw.crawler.strategies.crawl.CrawlUnsupportedException;
 import internal.hw.crawler.views.CommandOutput;
 import org.jsoup.Jsoup;
 import org.jsoup.nodes.Document;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
+import java.io.IOException;
 import java.net.URL;
 import java.util.List;
 import java.util.Objects;
 
 public class CrawlCommand implements Command {
+    private static final Logger log = LoggerFactory.getLogger(CrawlCommand.class);
     private final ArticleRepository repository;
     private final CommandOutput out;
     private final CrawlStrategyFactory crawlStrategyFactory = new CrawlStrategyFactory();
@@ -34,15 +41,11 @@ public class CrawlCommand implements Command {
     }
 
     @Override
-    public void execute(String[] args) throws Exception {
+    public void execute(String[] args) {
         String urlRaw = args[1];
+        try {
             URL url = new URL(urlRaw);
             CrawlStrategy strategy = crawlStrategyFactory.getStrategy(url);
-        if (strategy == null) {
-            out.error("Unsupported URL: " + urlRaw);
-            return;
-        }
-
             Document doc = Jsoup.connect(url.toString()).timeout(5000).get();
             CrawlUtils.setProgressCallback(msg -> System.out.print("\r" + msg));
             try {
@@ -53,5 +56,18 @@ public class CrawlCommand implements Command {
             } finally {
                 CrawlUtils.clearProgressCallback();
             }
+        } catch (CrawlUnsupportedException e) {
+            out.error(e.getMessage());
+            log.warn("Unsupported URL: {}", urlRaw);
+        } catch (CrawlNetworkException e) {
+            out.error("Network error: " + e.getMessage());
+            log.error("Crawl network failure for {}", urlRaw, e);
+        } catch (CrawlParseException e) {
+            out.error("Parse error: " + e.getMessage());
+            log.error("Crawl parse failure for {}", urlRaw, e);
+        } catch (IOException e) {
+            out.error("I/O error: " + e.getMessage());
+            log.error("Crawl I/O failure for {}", urlRaw, e);
+        }
     }
 }

src/main/java/internal/hw/crawler/strategies/crawl/CrawlException.java

@@ -1,11 +0,0 @@
-package internal.hw.crawler.strategies.crawl;
-
-public class CrawlException extends Exception {
-    public CrawlException(String message) {
-        super(message);
-    }
-
-    public CrawlException(String message, Throwable cause) {
-        super(message, cause);
-    }
-}

src/main/java/internal/hw/crawler/strategies/crawl/CrawlNetworkException.java

@@ -0,0 +1,34 @@
+package internal.hw.crawler.strategies.crawl;
+
+import java.net.URL;
+
+public class CrawlNetworkException extends CrawlerException {
+    private final int statusCode;
+    private final int attempts;
+
+    public CrawlNetworkException(String message, URL url) {
+        this(message, null, url, -1, 0);
+    }
+
+    public CrawlNetworkException(String message, Throwable cause, URL url) {
+        this(message, cause, url, -1, 0);
+    }
+
+    public CrawlNetworkException(String message, Throwable cause, URL url, int attempts) {
+        this(message, cause, url, -1, attempts);
+    }
+
+    public CrawlNetworkException(String message, Throwable cause, URL url, int statusCode, int attempts) {
+        super(message, url, cause);
+        this.statusCode = statusCode;
+        this.attempts = attempts;
+    }
+
+    public int getStatusCode() {
+        return statusCode;
+    }
+
+    public int getAttempts() {
+        return attempts;
+    }
+}

src/main/java/internal/hw/crawler/strategies/crawl/CrawlParseException.java

@@ -0,0 +1,43 @@
+package internal.hw.crawler.strategies.crawl;
+
+import java.net.URL;
+
+public class CrawlParseException extends CrawlerException {
+    public CrawlParseException(String message) {
+        super(message);
+    }
+
+    public CrawlParseException(String message, URL url) {
+        super(message, url);
+    }
+
+    public CrawlParseException(String message, URL url, Throwable cause) {
+        super(message, url, cause);
+    }
+
+    public static class ElementNotFoundException extends CrawlParseException {
+        private final String selector;
+
+        public ElementNotFoundException(String selector, URL url) {
+            super("Missing element '" + selector + "' in page: " + url, url);
+            this.selector = selector;
+        }
+
+        public String getSelector() {
+            return selector;
+        }
+    }
+
+    public static class IdExtractionException extends CrawlParseException {
+        private final String pattern;
+
+        public IdExtractionException(URL url, String pattern) {
+            super("Cannot determine id for " + url + " (pattern: " + pattern + ")", url);
+            this.pattern = pattern;
+        }
+
+        public String getPattern() {
+            return pattern;
+        }
+    }
+}

src/main/java/internal/hw/crawler/strategies/crawl/CrawlStrategy.java

@@ -7,7 +7,7 @@ import java.net.URL;
 import java.util.List;
 
 public interface CrawlStrategy {
-    List<Article> parse(URL url, Document doc) throws CrawlException;
+    List<Article> parse(URL url, Document doc) throws CrawlerException;
 
     boolean supports(URL url);
 }

src/main/java/internal/hw/crawler/strategies/crawl/CrawlStrategyFactory.java

@@ -19,7 +19,7 @@ public class CrawlStrategyFactory {
                 return s;
             }
         }
-        return null;
+        throw new CrawlUnsupportedException(url);
     }
 
     public void register(CrawlStrategy strategy) {

src/main/java/internal/hw/crawler/strategies/crawl/CrawlUnsupportedException.java

@@ -0,0 +1,9 @@
+package internal.hw.crawler.strategies.crawl;
+
+import java.net.URL;
+
+public class CrawlUnsupportedException extends CrawlerException {
+    public CrawlUnsupportedException(URL url) {
+        super("Unsupported site: " + url, url);
+    }
+}

src/main/java/internal/hw/crawler/strategies/crawl/CrawlUtils.java

@@ -6,6 +6,7 @@ import org.jsoup.nodes.Element;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URL;
 import java.util.ArrayList;
@@ -48,6 +49,7 @@ public class CrawlUtils {
 
         int total = hrefs.size();
         AtomicInteger done = new AtomicInteger(0);
+        AtomicInteger errors = new AtomicInteger(0);
         ExecutorService executor = Executors.newFixedThreadPool(THREAD_POOL_SIZE);
         List<CompletableFuture<Article>> futures = new ArrayList<>(total);
 
@@ -57,8 +59,13 @@ public class CrawlUtils {
                     URL articleUrl = URI.create(href).toURL();
                     Document articleDoc = crawler.fetch(articleUrl);
                     return singleParser.apply(articleUrl, articleDoc);
-                } catch (Exception e) {
+                } catch (CrawlerException e) {
-                    log.warn("Failed to fetch article: {}", href, e);
+                    int failed = errors.incrementAndGet();
+                    log.warn("Failed [{}/{}]: {} — {}", failed, total, href, e.getMessage());
+                    return null;
+                } catch (MalformedURLException e) {
+                    int failed = errors.incrementAndGet();
+                    log.warn("Failed [{}/{}]: {} — malformed URL", failed, total, href);
                     return null;
                 } finally {
                     int completed = done.incrementAndGet();
@@ -72,6 +79,10 @@ public class CrawlUtils {
         executor.shutdown();
         CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
 
+        if (errors.get() > 0) {
+            log.warn("Crawl completed: {}/{} articles failed", errors.get(), total);
+        }
+
         return futures.stream()
                 .map(CompletableFuture::join)
                 .filter(Objects::nonNull)

src/main/java/internal/hw/crawler/strategies/crawl/CrawlerException.java

@@ -0,0 +1,31 @@
+package internal.hw.crawler.strategies.crawl;
+
+import java.net.URL;
+
+public abstract class CrawlerException extends RuntimeException {
+    private final URL url;
+
+    public CrawlerException(String message) {
+        super(message);
+        this.url = null;
+    }
+
+    public CrawlerException(String message, Throwable cause) {
+        super(message, cause);
+        this.url = null;
+    }
+
+    public CrawlerException(String message, URL url) {
+        super(message);
+        this.url = url;
+    }
+
+    public CrawlerException(String message, URL url, Throwable cause) {
+        super(message, cause);
+        this.url = url;
+    }
+
+    public URL getUrl() {
+        return url;
+    }
+}

src/main/java/internal/hw/crawler/strategies/crawl/HttpCrawler.java

@@ -5,6 +5,7 @@ import org.jsoup.nodes.Document;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.io.IOException;
 import java.net.URL;
 import java.util.concurrent.ThreadLocalRandom;
 
@@ -29,26 +30,36 @@ public class HttpCrawler {
         this.userAgent = userAgent;
     }
 
-    public Document fetch(URL url) throws Exception {
+    public Document fetch(URL url) throws CrawlNetworkException {
+        IOException lastError;
         for (int attempt = 0; attempt <= maxRetries; attempt++) {
             try {
                 return Jsoup.connect(url.toString())
                         .timeout(timeoutMillis)
                         .userAgent(userAgent)
                         .get();
-            } catch (Exception e) {
+            } catch (IOException e) {
+                lastError = e;
                 if (attempt < maxRetries) {
                     long delay = computeBackoff(attempt);
                     log.warn("Failed to fetch {}, attempt {}/{}: {}. Retrying in {}ms",
                             url, attempt + 1, maxRetries, e.getMessage(), delay);
+                    try {
                         Thread.sleep(delay);
+                    } catch (InterruptedException ie) {
+                        Thread.currentThread().interrupt();
+                        throw new CrawlNetworkException(
+                                "Interrupted while fetching " + url, ie, url, maxRetries + 1);
+                    }
                 } else {
                     log.error("Failed to fetch {} after {} attempts", url, maxRetries + 1);
-                    throw e;
+                    throw new CrawlNetworkException(
+                            "Failed to fetch " + url + " after " + (maxRetries + 1) + " attempts",
+                            lastError, url, maxRetries + 1);
                 }
             }
         }
-        throw new RuntimeException("Unreachable");
+        throw new CrawlNetworkException("Unreachable", url);
     }
 
     public void rateLimit() throws InterruptedException {

src/main/java/internal/hw/crawler/strategies/crawl/IthomeCrawlStrategy.java

@@ -24,12 +24,12 @@ public class IthomeCrawlStrategy implements CrawlStrategy {
     }
 
     @Override
-    public List<Article> parse(URL url, Document doc) throws CrawlException {
+    public List<Article> parse(URL url, Document doc) throws CrawlParseException {
         if (isHomepage(url)) {
             return CrawlUtils.parseHomepage(doc, idRegex, (articleUrl, articleDoc) -> {
                 try {
                     return parseSingle(articleUrl, articleDoc);
-                } catch (CrawlException e) {
+                } catch (CrawlParseException e) {
                     log.warn("Failed to parse article: {}", articleUrl, e);
                     return null;
                 }
@@ -44,23 +44,23 @@ public class IthomeCrawlStrategy implements CrawlStrategy {
         return (path == null || path.isEmpty() || path.equals("/"));
     }
 
-    private Article parseSingle(URL url, Document doc) throws CrawlException {
+    private Article parseSingle(URL url, Document doc) throws CrawlParseException {
         Matcher matcher = idRegex.matcher(url.getPath());
         if (!matcher.find()) {
-            throw new CrawlException(String.format("Cannot determine id for %s", url));
+            throw new CrawlParseException.IdExtractionException(url, idRegex.pattern());
         }
 
         String id = String.format("%s-%s-%s", matcher.group(1), matcher.group(2), matcher.group(3));
 
         Element h1 = doc.selectFirst("h1");
         if (h1 == null) {
-            throw new CrawlException("Missing <h1> element in page: " + url);
+            throw new CrawlParseException.ElementNotFoundException("h1", url);
         }
         String title = h1.text();
 
         Element paragraph = doc.selectFirst("#paragraph");
         if (paragraph == null) {
-            throw new CrawlException("Missing #paragraph element in page: " + url);
+            throw new CrawlParseException.ElementNotFoundException("#paragraph", url);
         }
         String content = paragraph.text();
 

src/main/java/internal/hw/crawler/strategies/crawl/NeteaseNewsCrawlStrategy.java

@@ -25,12 +25,12 @@ public class NeteaseNewsCrawlStrategy implements CrawlStrategy {
     }
 
     @Override
-    public List<Article> parse(URL url, Document doc) throws CrawlException {
+    public List<Article> parse(URL url, Document doc) throws CrawlParseException {
         if (isHomepage(url)) {
             return CrawlUtils.parseHomepage(doc, idRegex, (articleUrl, articleDoc) -> {
                 try {
                     return parseSingle(articleUrl, articleDoc);
-                } catch (CrawlException e) {
+                } catch (CrawlParseException e) {
                     log.warn("Failed to parse article: {}", articleUrl, e);
                     return null;
                 }
@@ -45,20 +45,20 @@ public class NeteaseNewsCrawlStrategy implements CrawlStrategy {
         return path == null || path.isEmpty() || path.equals("/");
     }
 
-    private Article parseSingle(URL url, Document doc) throws CrawlException {
+    private Article parseSingle(URL url, Document doc) throws CrawlParseException {
         Matcher matcher = idRegex.matcher(url.getPath());
         if (!matcher.find()) {
-            throw new CrawlException(String.format("Cannot determine id for %s", url));
+            throw new CrawlParseException.IdExtractionException(url, idRegex.pattern());
         }
 
         String id = matcher.group(1);
         Element titleEl = doc.selectFirst("h1.post_title");
-        if (titleEl == null) throw new CrawlException(String.format("Cannot find title for %s", url));
+        if (titleEl == null) throw new CrawlParseException.ElementNotFoundException("h1.post_title", url);
         String title = titleEl.text();
 
 
         Element contentEl = doc.selectFirst("div.post_body");
-        if (contentEl == null) throw new CrawlException(String.format("Cannot find content for %s", url));
+        if (contentEl == null) throw new CrawlParseException.ElementNotFoundException("div.post_body", url);
         String content = contentEl.text();
 
         Article article = new Article();

src/main/java/internal/hw/crawler/strategies/crawl/PeopleCnCrawlStrategy.java

@@ -31,12 +31,12 @@ public class PeopleCnCrawlStrategy implements CrawlStrategy {
     }
 
     @Override
-    public List<Article> parse(URL url, Document doc) throws CrawlException {
+    public List<Article> parse(URL url, Document doc) throws CrawlParseException {
         if (isHomepage(url)) {
             return CrawlUtils.parseHomepage(doc, idRegex, (articleUrl, articleDoc) -> {
                 try {
                     return parseSingle(articleUrl, articleDoc);
-                } catch (CrawlException e) {
+                } catch (CrawlParseException e) {
                     log.warn("Failed to parse article: {}", articleUrl, e);
                     return null;
                 }
@@ -55,15 +55,15 @@ public class PeopleCnCrawlStrategy implements CrawlStrategy {
         return path == null || path.isEmpty() || path.equals("/");
     }
 
-    private Article parseSingle(URL url, Document doc) throws CrawlException {
+    private Article parseSingle(URL url, Document doc) throws CrawlParseException {
         Matcher matcher = idRegex.matcher(url.getPath());
         if (!matcher.find()) {
-            throw new CrawlException(String.format("Cannot determine id for %s", url));
+            throw new CrawlParseException.IdExtractionException(url, idRegex.pattern());
         }
 
         String id = String.format("%s%s-c%s-%s", matcher.group(1), matcher.group(2), matcher.group(3), matcher.group(4));
         Element titleEl = doc.selectFirst(".layout.rm_txt h1");
-        if (titleEl == null) throw new CrawlException(String.format("Cannot find title for %s", url));
+        if (titleEl == null) throw new CrawlParseException.ElementNotFoundException(".layout.rm_txt h1", url);
         String title = titleEl.text();
 
         Set<String> authors = new HashSet<>();
@@ -73,7 +73,7 @@ public class PeopleCnCrawlStrategy implements CrawlStrategy {
         }
 
         Element contentEl = doc.selectFirst("div#rm_txt_zw");
-        if (contentEl == null) throw new CrawlException(String.format("Cannot find content for %s", url));
+        if (contentEl == null) throw new CrawlParseException.ElementNotFoundException("div#rm_txt_zw", url);
         String content = contentEl.text();
 
         Article article = new Article();