Regular expression to get an attribute from HTML tag

java, regex

Solution

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:

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

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.

Problem

Original source