Merge pull request #556 from zhuyuesut/master

增加对零宽断言的支持

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

@@ -26,14 +26,16 @@ public class RegexSelector implements Selector {
         if (StringUtils.isBlank(regexStr)) {
             throw new IllegalArgumentException("regex must not be empty");
         }
+        
+        try {
+            regex = Pattern.compile(regexStr, Pattern.DOTALL | Pattern.CASE_INSENSITIVE);
             // Check bracket for regex group. Add default group 1 if there is no group.
             // Only check if there exists the valid left parenthesis, leave regexp validation for Pattern.
-        if ( ! hasGroup(regexStr) ){
+            if ( regex.matcher("").groupCount() == 0 ){
                 regexStr = "(" + regexStr + ")";
+                regex = Pattern.compile(regexStr, Pattern.DOTALL | Pattern.CASE_INSENSITIVE);
             }
             this.regexStr = regexStr;
-        try {
-            regex = Pattern.compile(regexStr, Pattern.DOTALL | Pattern.CASE_INSENSITIVE);
         } catch (PatternSyntaxException e) {
             throw new IllegalArgumentException("invalid regex", e);
         }
@@ -44,30 +46,6 @@ public class RegexSelector implements Selector {
         this(regexStr, 1);
     }
 
-    private boolean hasGroup(String regexStr) {
-        if (StringUtils.countMatches(regexStr, "(") - StringUtils.countMatches(regexStr, "\\(") ==
-                StringUtils.countMatches(regexStr, "(?:") - StringUtils.countMatches(regexStr, "\\(?:")){
-            return false;
-        }
-        if (StringUtils.countMatches(regexStr, "(") - StringUtils.countMatches(regexStr, "\\(") ==
-                StringUtils.countMatches(regexStr, "(?=") - StringUtils.countMatches(regexStr, "\\(?=") ) {
-            return false;
-        }
-        if (StringUtils.countMatches(regexStr, "(") - StringUtils.countMatches(regexStr, "\\(") ==
-                StringUtils.countMatches(regexStr, "(?<") - StringUtils.countMatches(regexStr, "\\(?<") ) {
-            return false;
-        }
-        if (StringUtils.countMatches(regexStr, "(") - StringUtils.countMatches(regexStr, "\\(") ==
-                StringUtils.countMatches(regexStr, "(?!") - StringUtils.countMatches(regexStr, "\\(?!") ) {
-            return false;
-        }
-        if (StringUtils.countMatches(regexStr, "(") - StringUtils.countMatches(regexStr, "\\(") ==
-                StringUtils.countMatches(regexStr, "(?#") - StringUtils.countMatches(regexStr, "\\(?#") ) {
-            return false;
-        }
-        return true;
-    }
-
     @Override
     public String select(String text) {
         return selectGroup(text).get(group);

webmagic-core/src/test/java/us/codecraft/webmagic/selector/RegexSelectorTest.java

@@ -25,8 +25,8 @@ public class RegexSelectorTest {
 
     @Test
     public void testRegexWithZeroWidthAssertions() {
-        String regex = "^.*(?=\\?)";
-        String source = "hello world?xxxx";
+        String regex = "^.*(?=\\?)(?!\\?yy)";
+        String source = "hello world?xx?yy";
         RegexSelector regexSelector = new RegexSelector(regex);
         String select = regexSelector.select(source);
         Assertions.assertThat(select).isEqualTo("hello world");