如何使用Java正则表达式提取特定单词前后的字符串

Question

I need to extract a string after opResult and before another string (word+ '=')

For example:

testest=false opResult=Critical extension not supported random=abc srcPort=10

So I should extract out Critical extension not supported , before the next word with an equals sign.

Also, it should also work if there is no other string at the back, meaning I should get the same result with the below example.

typesOnly=false opResult=Critical extension not supported

The regular expression I have currently extracted everything before the last '=' sign.

opResult=(\S.*)(\s\w+=)

Answer 1

We can try matching/extracting using the following pattern:

.*opResult=(.*?)(?:\\s*\\S+=.*|$)

The trick here is in being able to articulate when the next key begins, and then to not extract it.

String line = "testest=false opResult=Critical extension not supported random=abc srcPort=10";
String pattern = ".*opResult=(.*?)(?:\\s*\\S+=.*|$)";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(line);
if (m.find( )) {
    System.out.println(m.group(1));
}

Output:

Critical extension not supported

Demo here:

Rextester

Answer 2

You should work with positive lookbehind and positive lookahead and a lazy quantifier for the text in between

(?<=opResult=).*?(?=\s*\S*=)

You can see the results on regex101 .

Answer 3

We need to find text after 'opResult=' before the next blankspace(\\s)word(\\w+) followed by an equals sign (?==) and whatever follows (.*)

Pattern becomes

.*opResult=([\w|\s]+)(\s\w+(?==).*)

Here's the link to Regex101