- [x] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [x] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: 2.7.4
* Operating System version: Darwin Kernel Version 18.7.0
* Java version: 1.8.0_181-b13)

### Steps to reproduce this issue

1. invoke `StringUtils.split("d,1,2,4", 'a')`
2. invoke `"d,1,2,4".split("a")`

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

`StringUtils.split("d,1,2,4", 'a')` should return `["d,1,2,4"]` just like `"d,1,2,4".split("a")`.

### Actual Result

empty array.

return "null";
        } else if (obj instanceof String) {
            return (String) obj;
        } else {
            String str = obj.toString();
            return str != null ? str : "";
        }
    }
    /**
     * @param rawParameters format like '[{a:b},{c:d}]'
     * @return
     */
    public static Map<String, String> parseParameters(String rawParameters) {
        Matcher matcher = PARAMETERS_PATTERN.matcher(rawParameters);
        if (!matcher.matches()) {
            return Collections.emptyMap();
        }
        String pairs = matcher.group(1);
        String[] pairArr = pairs.split("\\s*,\\s*");
        Map<String, String> parameters = new HashMap<>();
        for (String pair : pairArr) {
            Matcher pairMatcher = PAIR_PARAMETERS_PATTERN.matcher(pair);
            if (pairMatcher.matches()) {
                parameters.put(pairMatcher.group(1), pairMatcher.group(2));
            }
        }
        return parameters;
    }
}