add more option to extractors

webmagic-core/src/main/java/us/codecraft/webmagic/selector/CssSelector.java

@@ -19,10 +19,17 @@ public class CssSelector implements Selector {
 
     private String selectorText;
 
+    private String attrName;
+
     public CssSelector(String selectorText) {
         this.selectorText = selectorText;
     }
 
+    public CssSelector(String selectorText, String attrName) {
+        this.selectorText = selectorText;
+        this.attrName = attrName;
+    }
+
     @Override
     public String select(String text) {
         Document doc = Jsoup.parse(text);
@@ -30,7 +37,15 @@ public class CssSelector implements Selector {
         if (CollectionUtils.isEmpty(elements)) {
             return null;
         }
-        return elements.get(0).outerHtml();
+        return getValue(elements.get(0));
+    }
+
+    private String getValue(Element element) {
+        if (attrName == null) {
+            return element.outerHtml();
+        } else {
+            return element.attr(attrName);
+        }
     }
 
     @Override
@@ -40,7 +55,10 @@ public class CssSelector implements Selector {
         Elements elements = doc.select(selectorText);
         if (CollectionUtils.isNotEmpty(elements)) {
             for (Element element : elements) {
-                strings.add(element.outerHtml());
+                String value = getValue(element);
+                if (value != null) {
+                    strings.add(value);
+                }
             }
         }
         return strings;

webmagic-core/src/main/java/us/codecraft/webmagic/selector/Html.java

@@ -69,4 +69,10 @@ public class Html extends PlainText {
         return selectList(cssSelector, strings);
     }
 
+    @Override
+    public Selectable $(String selector, String attrName) {
+        CssSelector cssSelector = new CssSelector(selector, attrName);
+        return selectList(cssSelector, strings);
+    }
+
 }

webmagic-core/src/main/java/us/codecraft/webmagic/selector/PlainText.java

@@ -40,6 +40,11 @@ public class PlainText implements Selectable {
         throw new UnsupportedOperationException();
     }
 
+    @Override
+    public Selectable $(String selector, String attrName) {
+        throw new UnsupportedOperationException();
+    }
+
     @Override
     public Selectable smartContent() {
         throw new UnsupportedOperationException();
@@ -56,6 +61,12 @@ public class PlainText implements Selectable {
         return selectList(regexSelector, strings);
     }
 
+    @Override
+    public Selectable regex(String regex, int group) {
+        RegexSelector regexSelector = SelectorFactory.getInstatnce().newRegexSelector(regex, group);
+        return selectList(regexSelector, strings);
+    }
+
     protected Selectable select(Selector selector, List<String> strings) {
         List<String> results = new ArrayList<String>();
         for (String string : strings) {

webmagic-core/src/main/java/us/codecraft/webmagic/selector/Selectable.java

@@ -26,6 +26,15 @@ public interface Selectable {
      */
     public Selectable $(String selector);
 
+    /**
+     * select list with css selector
+     *
+     * @param selector css selector expression
+     * @param attrName attribute name of css selector
+     * @return new Selectable after extract
+     */
+    public Selectable $(String selector, String attrName);
+
     /**
      * select smart content with ReadAbility algorithm
      *
@@ -41,13 +50,22 @@ public interface Selectable {
     public Selectable links();
 
     /**
-     * select list with regex
+     * select list with regex, default group is group 1
      *
      * @param regex
      * @return new Selectable after extract
      */
     public Selectable regex(String regex);
 
+    /**
+     * select list with regex
+     *
+     * @param regex
+     * @param group
+     * @return new Selectable after extract
+     */
+    public Selectable regex(String regex, int group);
+
     /**
      * replace with regex
      *

webmagic-core/src/main/java/us/codecraft/webmagic/selector/SelectorFactory.java

@@ -26,6 +26,10 @@ public class SelectorFactory {
         return newSelector(RegexSelector.class, regex);
     }
 
+    public RegexSelector newRegexSelector(String regex, int group) {
+        return newSelector(RegexSelector.class, regex, String.valueOf(group));
+    }
+
     public ReplaceSelector newReplaceSelector(String regex, String replacement) {
         return newSelector(ReplaceSelector.class, regex, replacement);
     }