Krishna Kumar Krishna Kumar - 11 months ago 17
Java Question

Regular expression to get an attribute from HTML tag

I am looking for a regular expression that can get me src (case insensitive) tag from following HTML snippets in java.

<html><img src="kk.gif" alt="text"/></html>
<html><img src='kk.gif' alt="text"/></html>
<html><img src = "kk.gif" alt="text"/></html>


One possibility:

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

is a possibility (if matched case-insensitively). It's a bit of a mess, and deliberately ignores the case where quotes aren't used. To represent it without worrying about string escapes:


This matches:

  • <img
  • one or more characters that aren't > (i.e. possible other attributes)
  • src
  • optional whitespace
  • =
  • optional whitespace
  • starting delimiter of ' or "
  • image source (which may not include a single or double quote)
  • ending delimiter
  • although the expression can stop here, I then added:
    • zero or more characters that are not > (more possible attributes)
    • > to close the tag

Things to note:

  • If you want to include the src= as well, move the open bracket further left :-)
  • This does not care about delimiter balancing or attribute values without delimiters, and it can also choke on badly-formed attributes (such as attributes that include > or image sources that include ' or ").
  • Parsing HTML with regular expressions like this is non-trivial, and at best a quick hack that works in the majority of cases.