Question

<img[^>]+src\\s*=\\s*['\"]([^'\"]+)['\"][^>]*>

I know this regex expression is used to retrieve the value of src. Can anyone teach me how i should interpret this expression? stucked at it.

Answer 1

Explaining:

• <img matches exactly the string "<img"
• [^>]+ matches multiple times of everything but >, so the tag will not be closed
• src matches exactly the string “src”
• \\s* matches any number of whitespace characters
• = matches exactly the string “=”
• \\s* matches any number of whitespace characters
• ['\"] matches the two quotes. The double quote is escaped, because otherwise it will terminate the string of the regex
• ([^'\"]+) mathches multiple times everything but quotes. The contents are wrapped in brackets, so that they are declared as group and can be retrieved later
• ['\"] matches the two quotes. The double quote is escaped, because otherwise it will terminate the string of the regex
• [^>]* matches the remaining non ">" characters
• > matches exactly the string ">", the closing bracket of the tag.

I would not agree this expression is a crap, just a bit complex.

EDIT Here you go some examplary code:

String str = "<img[^>]+src\\s*=\\s*['\"]([^'\"]+)['\"][^>]*>";
String text = "<img alt=\"booo\" src=\"image.jpg\"/>";
Pattern pattern = Pattern.compile (str);
Matcher matcher = pattern.matcher (text);

if (matcher.matches ())
{
      int n = matcher.groupCount ();
      for (int i = 0; i <= n; ++i)
          System.out.println (matcher.group (i));
}

The output is:

<img alt="booo" src="image.jpg"/>
image.jpg

So matcher.group(1) returns what you want. experiment a bit with this code.