better exception handling

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

@@ -10,7 +10,7 @@ public class Main {
         MainController controller = new MainController(view);
         ArticleRepository repository = new ArticleRepository();
 
-        controller.registerCommand(new ExitCommand());
+        controller.registerCommand(new ExitCommand(view));
         controller.registerCommand(new CrawlCommand(repository, view));
         controller.registerCommand(new ListCommand(repository, view));
         controller.registerCommand(new SaveCommand(repository, view));
@@ -18,7 +18,17 @@ public class Main {
 
         view.printSuccess("Welcome to crawler. Type `help` for a list of available commands.");
         while (true) {
-            controller.handleInput(view.readLine());
+            try {
+                String line = view.readLine();
+                // stdin 读取异常时退出
+                if (line == null) {
+                    controller.handleInput(new ExitCommand(view).getName());
+                    break;
+                }
+                controller.handleInput(line);
+            } catch (Exception e) {
+                view.printError("Unexpected error: " + e.getMessage());
+            }
         }
     }
 }

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

@@ -43,7 +43,11 @@ public class MainController {
             return;
         }
 
+        try {
             command.execute(args);
+        } catch (Exception e) {
+            view.printError("Command failed: " + e.getMessage());
+        }
     }
 
     private boolean validateArgs(Command command, String[] args) {

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

@@ -9,5 +9,5 @@ public interface Command {
         return List.of();
     }
 
-    void execute(String[] args);
+    void execute(String[] args) throws Exception;
 }

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

@@ -32,8 +32,7 @@ public class CrawlCommand implements Command {
     }
 
     @Override
-    public void execute(String[] args) {
+    public void execute(String[] args) throws Exception {
-        try {
         String urlRaw = args[1];
         URL url = new URL(urlRaw);
         CrawlStrategy strategy = crawlStrategyFactory.getStrategy(url);
@@ -45,11 +44,10 @@ public class CrawlCommand implements Command {
         Document doc = Jsoup.parse(url, 5000);
         List<Article> articles = strategy.parse(url, doc);
         for (Article article : articles) {
+            if (article != null) {
                 repository.add(article);
             }
-            out.success(String.format("Crawled %d articles from %s", articles.size(), urlRaw));
-        } catch (Exception e) {
-            throw new RuntimeException(e);
         }
+        out.success(String.format("Crawled %d articles from %s", articles.size(), urlRaw));
     }
 }

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

@@ -1,6 +1,14 @@
 package internal.hw.crawler.commands;
 
+import internal.hw.crawler.views.CommandOutput;
+
 public class ExitCommand implements Command {
+    private final CommandOutput out;
+
+    public ExitCommand(CommandOutput out) {
+        this.out = out;
+    }
+
     @Override
     public String getName() {
         return "exit";
@@ -8,6 +16,7 @@ public class ExitCommand implements Command {
 
     @Override
     public void execute(String[] args) {
+        out.info("Goodbye.");
         System.exit(0);
     }
 }

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

@@ -5,6 +5,7 @@ import internal.hw.crawler.models.Article;
 import internal.hw.crawler.repositories.ArticleRepository;
 import internal.hw.crawler.views.CommandOutput;
 
+import com.google.gson.JsonSyntaxException;
 import java.io.*;
 import java.util.*;
 import java.util.stream.Collectors;
@@ -25,7 +26,7 @@ public class SaveCommand implements Command {
     }
 
     @Override
-    public void execute(String[] args) {
+    public void execute(String[] args) throws IOException {
         String filename = "articles.output.json";
 
         List<Article> articles = getExistingArticles(filename);
@@ -38,11 +39,9 @@ public class SaveCommand implements Command {
 
         Article[] articlesToSave = articleMap.values().toArray(new Article[0]);
 
-        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filename));) {
+        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filename))) {
             writer.write(gson.toJson(articlesToSave));
             out.success(String.format("Wrote %d articles to %s", articlesToSave.length, filename));
-        } catch (IOException e) {
-            throw new RuntimeException(e);
         }
     }
 
@@ -54,7 +53,10 @@ public class SaveCommand implements Command {
         try (BufferedReader reader = new BufferedReader(new FileReader(filename))) {
             Article[] articles = gson.fromJson(reader, Article[].class);
             return Arrays.asList(articles);
-        } catch (IOException e) {
+        } catch (FileNotFoundException e) {
+            return List.of();
+        } catch (IOException | JsonSyntaxException e) {
+            out.error("Failed to read existing articles: " + e.getMessage());
             return List.of();
         }
     }

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

@@ -2,6 +2,7 @@ package internal.hw.crawler.strategies.crawl;
 
 import internal.hw.crawler.models.Article;
 import org.jsoup.nodes.Document;
+import org.jsoup.nodes.Element;
 
 import java.net.URL;
 import java.util.HashSet;
@@ -25,17 +26,29 @@ public class IthomeCrawlStrategy implements CrawlStrategy {
 
     private Article parseSingle(URL url, Document doc) throws CrawlException {
         Matcher matcher = idRegex.matcher(url.getPath());
-        if (!matcher.find()) throw new CrawlException(String.format("Cannot determine id for %s", url));
+        if (!matcher.find()) {
+            throw new CrawlException(String.format("Cannot determine id for %s", url));
+        }
 
         String id = String.format("%s-%s-%s", matcher.group(1), matcher.group(2), matcher.group(3));
-        String title = doc.selectFirst("h1").text();
-        String content = doc.selectFirst("#paragraph").text();
 
-        String authorRaw = doc.selectFirst("#author_baidu > strong").text();
+        Element h1 = doc.selectFirst("h1");
-        String editorRaw = doc.selectFirst("#editor_baidu > strong").text();
+        if (h1 == null) {
+            throw new CrawlException("Missing <h1> element in page: " + url);
+        }
+        String title = h1.text();
+
+        Element paragraph = doc.selectFirst("#paragraph");
+        if (paragraph == null) {
+            throw new CrawlException("Missing #paragraph element in page: " + url);
+        }
+        String content = paragraph.text();
+
+        Element authorEl = doc.selectFirst("#author_baidu > strong");
+        Element editorEl = doc.selectFirst("#editor_baidu > strong");
         Set<String> authors = new HashSet<>();
-        authors.add(authorRaw);
+        if (authorEl != null) authors.add(authorEl.text());
-        authors.add(editorRaw);
+        if (editorEl != null) authors.add(editorEl.text());
 
         Article article = new Article();
         article.setId(id);

src/main/java/internal/hw/crawler/views/ConsoleView.java

@@ -1,5 +1,6 @@
 package internal.hw.crawler.views;
 
+import java.util.NoSuchElementException;
 import java.util.Scanner;
 
 public class ConsoleView implements CommandOutput {
@@ -12,7 +13,11 @@ public class ConsoleView implements CommandOutput {
 
     public String readLine() {
         System.out.print("> ");
+        try {
             return scanner.nextLine();
+        } catch (NoSuchElementException | IllegalStateException e) {
+            return null;
+        }
     }
 
     @Override