正则表达式在要拆分的字符串中识别 JSON 使用：分隔符

Question

I have an input String which is being split using : (colon) as separator. This String can contain all string values OR possibly a json object itself as part of this incoming string.

For example:

Case#1: 123:HARRY_POTTER:ENGLAND:MALE

Case#2: 123:HARRY_POTTER:[{"key":"City", "value":"LONDON"}]:MALE

There is code in place that uses str.split(":") which is handling the case#1, but for case#2 since the json part of the string contains : (which are to be ignored while splitting), the program breaks.

I need a regex that could (1) identify the json in string and (2) a regex that would not split if : is preceded and followed by " ( ":" ) as it appears in JSON string.

So if the string is identifed to contain json i can use str.split(<regex-to-split-string-with-json>)

I arrived at these regex to match for a " preceding to : none of which are working unfortunately:

Negative Look Behind: (?<:\"): and (?<:\")[:]

Positive Look Behind: (?<=\"): and (?<=\")[:]

Please suggest!

Answer 1

Please try regex (?<=[a-zA-Z0-9\\]]): its working as expected for your both the cases:

import java.util.Arrays;

public class Solution {
    public static void main(String[] args) {
        String str = "123:HARRY_POTTER:[{\"key\":\"City\", \"value\":\"LONDON\"}]:MALE";
        String regex = "(?<=[a-zA-Z0-9\\]]):";
        String arr[] = str.split(regex);
        System.out.println("Length: " + arr.length);
        System.out.println(Arrays.toString(arr));
    }
}

Output:

Length: 4
[123, HARRY_POTTER, [{"key":"City", "value":"LONDON"}], MALE]

Answer 2

For the example data, perhaps it would be enough to either match from [ till ] or match any char except :

But as this data comes in mixed, it is not easy to determine what is actual valid json. You would still have to validate that afterwards.

Note that this is a brittle solution, and does not take any nesting of the square brackets into account.

\[[^]\[\r\n]+]|[^\r\n:]+

• \[[^]\[\r\n]+] Match from [...]
• | Or
• [^\r\n:]+ Match 1+ times any char except : or a newline

See a regex and Java demo.

Example

String regex = "\\[[^]\\[\\r\\n]+]|[^\\r\\n:]+";
String string = "123:HARRY_POTTER:[{\"key\":\"City\", \"value\":\"LONDON\"}]:MALE";

Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(string);

while (matcher.find()) {
    System.out.println(matcher.group(0));
}

Output

123
HARRY_POTTER
[{"key":"City", "value":"LONDON"}]
MALE