basic crawling

pom.xml

@@ -12,4 +12,11 @@
         <maven.compiler.target>11</maven.compiler.target>
     </properties>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.jsoup</groupId>
+            <artifactId>jsoup</artifactId>
+            <version>1.22.2</version>
+        </dependency>
+    </dependencies>
 </project>

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

@@ -1,11 +1,18 @@
 package internal.hw.crawler.commands;
 
+import internal.hw.crawler.models.Article;
 import internal.hw.crawler.repositories.ArticleRepository;
+import internal.hw.crawler.strategies.crawl.CrawlStrategy;
+import internal.hw.crawler.strategies.crawl.CrawlStrategyFactory;
+import org.jsoup.Jsoup;
+import org.jsoup.nodes.Document;
 
+import java.net.URL;
 import java.util.List;
 
 public class CrawlCommand implements Command {
-    private ArticleRepository repository;
+    private final ArticleRepository repository;
+    private final CrawlStrategyFactory crawlStrategyFactory = new CrawlStrategyFactory();
 
     public CrawlCommand(ArticleRepository repository) {
         this.repository = repository;
@@ -23,6 +30,22 @@ public class CrawlCommand implements Command {
 
     @Override
     public void execute(String[] args) {
-        System.out.printf("Will crawl %s%n", args[1]);
+        try {
+            String urlRaw = args[1];
+            URL url = new URL(urlRaw);
+            CrawlStrategy strategy = crawlStrategyFactory.getStrategy(url);
+            if (strategy == null) {
+                System.err.println("Unsupported URL: " + urlRaw);
+                return;
+            }
+
+            Document doc = Jsoup.parse(url, 5000);
+            List<Article> articles = strategy.parse(url, doc);
+            for (Article article : articles) {
+                repository.add(article);
+            }
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
     }
 }

src/main/java/internal/hw/crawler/models/Article.java

@@ -1,21 +1,28 @@
 package internal.hw.crawler.models;
 
+import java.net.URL;
+import java.util.Set;
+
 public class Article {
-    private String url;
+    private String id;
+    private URL url;
     private String title;
+    private Set<String> authors;
     private String content;
 
-    public Article(String url, String title, String content) {
-        this.url = url;
-        this.title = title;
-        this.content = content;
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
     }
 
-    public String getUrl() {
+    public URL getUrl() {
         return url;
     }
 
-    public void setUrl(String url) {
+    public void setUrl(URL url) {
         this.url = url;
     }
 
@@ -27,6 +34,14 @@ public class Article {
         this.title = title;
     }
 
+    public Set<String> getAuthors() {
+        return authors;
+    }
+
+    public void setAuthors(Set<String> authors) {
+        this.authors = authors;
+    }
+
     public String getContent() {
         return content;
     }
@@ -37,6 +52,6 @@ public class Article {
 
     @Override
     public String toString() {
-        return String.format("Article{%s}", url);
+        return String.format("Article{%s (%s)}", title, url);
     }
 }

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

@@ -0,0 +1,11 @@
+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/CrawlStrategy.java

@@ -0,0 +1,13 @@
+package internal.hw.crawler.strategies.crawl;
+
+import internal.hw.crawler.models.Article;
+import org.jsoup.nodes.Document;
+
+import java.net.URL;
+import java.util.List;
+
+public interface CrawlStrategy {
+    List<Article> parse(URL url, Document doc) throws CrawlException;
+
+    boolean supports(URL url);
+}

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

@@ -0,0 +1,27 @@
+package internal.hw.crawler.strategies.crawl;
+
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.List;
+
+public class CrawlStrategyFactory {
+    private final List<CrawlStrategy> strategies = new ArrayList<>();
+
+    public CrawlStrategyFactory() {
+        register(new IthomeCrawlStrategy());
+    }
+
+    public CrawlStrategy getStrategy(URL url) {
+        for (CrawlStrategy s : strategies) {
+            if (s.supports(url)) {
+                return s;
+            }
+        }
+        return null;
+    }
+
+    public void register(CrawlStrategy strategy) {
+        strategies.add(strategy);
+    }
+}
+

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

@@ -0,0 +1,48 @@
+package internal.hw.crawler.strategies.crawl;
+
+import internal.hw.crawler.models.Article;
+import org.jsoup.nodes.Document;
+
+import java.net.URL;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class IthomeCrawlStrategy implements CrawlStrategy {
+    private final Pattern idRegex = Pattern.compile("(\\d+)/(\\d+)/(\\d+)\\.htm");
+
+    @Override
+    public boolean supports(URL url) {
+        return url.getHost().endsWith("ithome.com");
+    }
+
+    @Override
+    public List<Article> parse(URL url, Document doc) throws CrawlException {
+        return List.of(parseSingle(url, doc));
+    }
+
+    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));
+
+        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();
+        String editorRaw = doc.selectFirst("#editor_baidu > strong").text();
+        Set<String> authors = new HashSet<>();
+        authors.add(authorRaw);
+        authors.add(editorRaw);
+
+        Article article = new Article();
+        article.setId(id);
+        article.setUrl(url);
+        article.setTitle(title);
+        article.setAuthors(authors);
+        article.setContent(content);
+        return article;
+    }
+}