java use regular expression in String.split to prepare json argument

Question

I have a csv file which contain this type of document：

{""cast_id"": 10, ""character"": ""Mushu (voice)"", ""credit_id"": ""52fe43a09251416c75017cbb"", ""gender"": 2, ""id"": 776, ""name"": ""Eddie Murphy"", ""order"": 0}, {""cast_id"": 62, ""character"": ""[Singing voice]"", ""credit_id"": ""597a65c8925141233d0000bb"", ""gender"": 2, ""id"": 18897, ""name"": ""Jackie Chan"", ""order"": 1}, {""cast_id"": 16, ""character"": ""Mulan (voice)"", ""credit_id"": ""52fe43a09251416c75017cd5"", ""gender"": 1, ""id"": 21702, ""name"": ""Ming-Na Wen"", ""order"": 2}

I used this regular expression first to change quadruple quote to double quote:

String newResult = result.replaceAll("\"{2}", "\"");

Then I use this regular expression to split this string:

String[] jsonResult = newResult.split(", (?![^{]*\\})");

However, it seperates the string into this:

{"cast_id": 10, "character": "Mushu (voice)", "credit_id": "52fe43a09251416c75017cbb", "gender": 2, "id": 776, "name": "Eddie Murphy", "order": 0}

{"cast_id": 62

"character": "[Singing voice

something else then

{"cast_id": 16, "character": "Mulan (voice)", "credit_id": "52fe43a09251416c75017cd5", "gender": 1, "id": 21702, "name": "Ming-Na Wen", "order": 2}

So my regular expression failed when it meets square brackets [], can I have some help with this?

I tried to use http://www.regexplanet.com/advanced/java/index.html but I don't understand what I should put in option, replacement and input. How do I use this website?

Thanks

I would recommend you use a JSON parser instead of regular expressions. It will save you a lot of headaches — Jeroen Steenbeeke
– Jeroen Steenbeeke, Commented Nov 30, 2017 at 8:53
I tried Json-simple, But json-simple only takes in standard json type. That's why I am changing the string to individual standard json string, then I would parse it. — Byron
– Byron, Commented Nov 30, 2017 at 8:55
is there a method in json-simple or other package which split a string of multiple json input separated by comma? I couldn't find it in json-simple — Byron
– Byron, Commented Nov 30, 2017 at 8:57
Like the ones in his examples. mkyong.com/java/json-simple-example-read-and-write-json My data is a string of several json separated by comma. that's why I need to separate them and then parse them — Byron
– Byron, Commented Nov 30, 2017 at 9:00

Mick · Accepted Answer · 2017-11-30 09:00:23Z

1

You are dealing with JSON data which has been saved as one column CSV file. :) Quotes will be escaped with double quotes in CSV, so you could just use a CSV library to read your file. As I said, you should expect to get just one column - one value containing your JSON. Then you use a JSON library to parse your JSON.

=> you would not need to implement any parsing at all.

answered Nov 30, 2017 at 9:00

Mick

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4 Comments

Byron Over a year ago

what do you mean by "Quotes will be escaped with double quotes in CSV" ? Also is there a method which automatically read csv file or string? Thanks

Mick Over a year ago

Its part of the CSV specification (creativyst.com/Doc/Articles/CSV/CSV01.htm) Text data is usually enclosed in quotes and if you want to use quotes within your text (like your JSON test), you write a double quote. If I were you, I would try to read the proper JSON first with something like this (commons.apache.org/proper/commons-csv) and after that take care of parsing the JSON. Step 1 Google: "Java read CSV library" Step 2 Google: "Java parse JSON"

Byron Over a year ago

I think I see what you mean. Could you tell you how to install common csv library on eclipse? I see it's not jar file.

Mick Over a year ago

Google "apache commons csv jar" => commons.apache.org/proper/commons-csv/download_csv.cgi

Oscar de Leeuw · Accepted Answer · 2017-11-30 09:15:46Z

0

You should be looking for the pattern }, { The regex: (?<=\}), (?=\{) does just that. Your regex will give a false positive if a } is missing at the end of the string.

(Tested with https://regex101.com/)

After that you can parse each string as JSON, use a library for that.

answered Nov 30, 2017 at 9:15

Oscar de Leeuw

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Comments

Malte Hartwig · Accepted Answer · 2017-11-30 10:20:12Z

As others recommended, a parser would be a better solution than splitting yourself. Regular expressions run into limitations when you get nested brackets, for example. I used Google's Gson library, and tweaking your input slightly produced the desired split. The important step was to turn your input into a JSON array, otherwise the parser would fail after the first element:

// Pre-processed your input to remove the double double quotes
String input = "{'cast_id': 10, 'character': 'Mushu (voice)', 'credit_id': '52fe43a09251416c75017cbb', 'gender': 2, 'id': 776, 'name': 'Eddie Murphy', 'order': 0}, {'cast_id': 62, 'character': '[Singing voice]', 'credit_id': '597a65c8925141233d0000bb', 'gender': 2, 'id': 18897, 'name': 'Jackie Chan', 'order': 1}, {'cast_id': 16, 'character': 'Mulan (voice)', 'credit_id': '52fe43a09251416c75017cd5', 'gender': 1, 'id': 21702, 'name': 'Ming-Na Wen', 'order': 2}";

JsonArray array = new JsonParser().parse("[" + input + "]").getAsJsonArray();
for (int i = 0; i < array.size(); i++)
{
    System.out.println(array.get(i));
}

Output:

{"cast_id":10,"character":"Mushu (voice)","credit_id":"52fe43a09251416c75017cbb","gender":2,"id":776,"name":"Eddie Murphy","order":0}
{"cast_id":62,"character":"[Singing voice]","credit_id":"597a65c8925141233d0000bb","gender":2,"id":18897,"name":"Jackie Chan","order":1}
{"cast_id":16,"character":"Mulan (voice)","credit_id":"52fe43a09251416c75017cd5","gender":1,"id":21702,"name":"Ming-Na Wen","order":2}

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