Regular expression to get an attribute from HTML tag

Question

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

Answer 1

One possibility:

String imgRegex = "]+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:

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

This matches:

• 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.