Check whether the String is a Valid JSON String or not?

Question

I am trying to execute a SELECT SQL query and after that I need to loop through the ResultSet and get the columns and check whether the data I got back for those columns is a Valid JSON String or not.

Here columnsList is an ArrayList which will contain all the names of the Columns of a particular table.

ResultSet rs = preparedStatement.executeQuery();

while (rs.next()) {
    for (String column : columnsList.split(",")) {

        //check whether rs.getString(column) is a valid JSON String?
        if(rs.getString(column).ISvalid_JSON_String()) {

            System.out.println("Valid JSON String data")
        }
    }
}

I am not sure how should I check whether the data I got back for each column is a valid JSON String or not?

Any thoughts?

Answer 1

If you need to be sure it really is valid JSON you're going to need to parse it. A fast, simple, lightweight parser that I like is json-simple. Have a look at their examples here.

http://code.google.com/p/json-simple/wiki/DecodingExamples#Example_2_-_Faster_way:_Reuse_instance_of_JSONParser

Adapting your code I get:

JSONParser parser = new JSONParser();
ResultSet rs = preparedStatement.executeQuery();

while (rs.next()) {
    for (String column : columnsList.split(",")) {
        //check whether rs.getString(column) is a valid JSON String?
        try{ 
            parser.parse(rs.getString(column)); 
            System.out.println("Valid JSON String data");
        } catch (ParseException e) {
            System.out.printlnn("Invalid JSON String data");
        }
    }
}