Java Regex matching between curly braces

Question

I need to parse a log file and get the times and associated function call string This is stored in the log file as so: {\"time\" : \"2012-09-24T03:08:50\", \"message\" : \"C

Answer 1

you need to escape '{' & '}' with a '\'

so: "{(.*?)}" becomes: "\\{(.*?)\\}"

where you have to escape the '\' with another '\' first

see: http://www.regular-expressions.info/reference.html for a comprehensive list of characters that need escaping...

Answer 2

{} in regexp have special meaning, so they need to be escaped.

Usually escaping is achieved by preceeding the character to be escaped with a backslash. In a character class defined with square brackets, you shouldn't need to do this

So something like

Pattern.compile("\{[^{}]*\}");

Could be nearer to what you want to do

Answer 3

This works perfectly for non-nested brackets but for expressions like

(sum(x) * 100) / (sum(y) + sum(z))

[a-z]*[\{]+([a-zA-Z0-9]+)[\}]+ works.

Answer 4

Braces are special regex characters used for repetition groups, therefore you must escape them.

Pattern logEntry = Pattern.compile("\\{(.*?)\\}");

Simple tester:

 public static void main(String[] args) throws Exception {
        String x =  "{\"time\" : \"2012-09-24T03:08:50\", \"message\" : \"Call() started\"}";
        Pattern logEntry = Pattern.compile("\\{(.*?)\\}");
        Matcher matchPattern = logEntry.matcher(x);

        while(matchPattern.find()) {
            System.out.println(matchPattern.group(1));
        }

    }

Gives me:

"time" : "2012-09-24T03:08:50", "message" : "Call() started"

Answer 5

You should use a positive lookahead and lookbehind:

(?<=\{)([^\}]+)(?=\})

• (?<={) Matches everything followed by {
• ([^}]+) Matches any string not containing }
• (?={) Matches everything before {