Extract Json String from Mixed String with JAVA

Question

I have a large text file. Its mixed up more lines with various info

My requirement is retrieve json from Below mixed String line

Line :

PID: [0] [STM] [2016-12-01 00:00:00,135]  INFORMATION {com.priyan.JsonParser} -  My Req Body: { "amountTxn": { "paymentAmt": { "amtReserved": null, "totalAmtCharged": null, "chargingData": { "taxAmt": 10, "categoryCode": "MyApp" }, "totalAmountRefunded": null, "chargingInformation": { "amount": 1.5, "description": ["Test 01 (demo)"] } }, "userId": "tel:+2313215", "txnStatus": "Charged", "origCode": null, "seq": null } } TOKEN ID: 351351 {com.priyan.JsonParser}

I need to extract this json part only

{ "amountTxn": { "paymentAmt": { "amtReserved": null, "totalAmtCharged": null, "chargingData": { "taxAmt": 10, "categoryCode": "MyApp" }, "totalAmountRefunded": null, "chargingInformation": { "amount": 1.5, "description": ["Test 01 (demo)"] } }, "userId": "tel:+2313215", "txnStatus": "Charged", "origCode": null, "seq": null } }

Please help, Thanks

Does each line of the file has the same format till "... - My Req Body:..."?? — SachinSarawgi
– SachinSarawgi, Commented Dec 6, 2016 at 9:10
Well, this file has a specific pattern ? Like PID: ... My Req Body: JSON ... TOKEN ... You could use Regex or simply subString the json first find the good { } if you know exactly the format of the code before and after — AxelH
– AxelH, Commented Dec 6, 2016 at 9:10

arctic_Oak · Accepted Answer · 2019-07-17 13:39:13Z

There are two ways to achieve the solution:

Using Regex
Write your own parser to achieve the solution

Using Regex

Regex is not the recommended solution: They can be very inefficient sometimes. See this and this.

Even if you want regex, here is the solution:

see this

Write your own parser to achieve the solution:

void getJsonFromString(String input) {

        List<Character> stack = new ArrayList<Character>();
        List<String> jsons = new ArrayList<String>();
        String temp = "";
        for(char eachChar: input.toCharArray()) {
            if(stack.isEmpty() && eachChar == '{') {
                stack.add(eachChar);
                temp += eachChar;
            } else if(!stack.isEmpty()) {
                temp += eachChar;
                if(stack.get(stack.size()-1).equals('{') && eachChar == '}') {
                    stack.remove(stack.size()-1);
                    if(stack.isEmpty()) {
                        jsons.add(temp);
                        temp = "";
                    }
                }
                else if(eachChar == '{' || eachChar == '}')
                    stack.add(eachChar);
            } else if(temp.length()>0 && stack.isEmpty()) {
                jsons.add(temp);
                temp = "";
            }
        }
        for(String json: jsons)
            System.out.println(json);
    }

AxelH · Accepted Answer · 2016-12-06 09:16:17Z

4

This will find the position of the second bracket you need (because of INFORMATION and TOKEN block) and substring the content you need.

So basicly, I search the second (by finding the bracket after the first one) and same thing for the end. Then simply extract the String.

public static void main(String[] args){
        String s = "PID: [0] [STM] [2016-12-01 00:00:00,135]  INFORMATION {com.priyan.JsonParser} -  My Req Body: { \"amountTxn\": { \"paymentAmt\": { \"amtReserved\": null, \"totalAmtCharged\": null, \"chargingData\": { \"taxAmt\": 10, \"categoryCode\": \"MyApp\" }, \"totalAmountRefunded\": null, \"chargingInformation\": { \"amount\": 1.5, \"description\": [\"Test 01 (demo)\"] } }, \"userId\": \"tel:+2313215\", \"txnStatus\": \"Charged\", \"origCode\": null, \"seq\": null } } TOKEN ID: 351351 {com.priyan.JsonParser}";
        int begin = s.indexOf("{", s.indexOf("{") + 1);
        int end = s.lastIndexOf("}", s.lastIndexOf("}") - 1);
        s = s.substring(begin, end);
        System.out.println(s);
    }

This solution doesn't work if the text before and/or after don't have any bracket but can be update depending on other pattern.

answered Dec 6, 2016 at 9:16

AxelH

14.6k2 gold badges27 silver badges56 bronze badges

2 Comments

Priyanka Over a year ago

thnkz AxelH.This one works for me. can't use Json or Gson libraries for this task.?

AxelH Over a year ago

To extract the JSON from the String, I don't think so but I don't know everything about GSON. But is it really necessary, I mean the extraction is not really complicated.

Rakesh · Accepted Answer · 2016-12-06 09:15:24Z

3

You can use the regular expression ^.*Body:\s(.*)\sTOKEN.* to extract the data you want, provided the adjacent words on either side of the JSON data won't change and I mean exactly the words "Body: " (including the white space) and " TOKEN"

This regex basically extracts the text between "Body: " and " TOKEN"

answered Dec 6, 2016 at 9:15

Rakesh

4,3424 gold badges35 silver badges58 bronze badges

6 Comments

Priyanka Over a year ago

Noted & Thanks But I need to know whther any other options gave by Json libraries or not.!

Rakesh Over a year ago

Yes, like @CodeRunner mentions there are few JSON libs that can parse JSON string and create an object out of it. The problem is that your input string is not a valid JSON string. If you are reading this string from third party data then you are most probably out of luck.

Priyanka Over a year ago

its correct json. I tested with jsonlint web site too

Rakesh Over a year ago

I tested the entire string starting from PID: [0] ... on jsonlint and it gave validation error.

Priyanka Over a year ago

not entire string. from entire string i need to extract only that below json part

|

CodeRunner · Accepted Answer · 2016-12-06 09:15:55Z

2

Create a class which has a structure similar to JSON and then use Jackson [Java JSON parser (http://jackson.codehaus.org)] library. Please refer Parsing JSON File Java for more information

answered Dec 6, 2016 at 9:15

CodeRunner

1471 silver badge9 bronze badges

2 Comments

Priyanka Over a year ago

thnkz @CodeRunner

AxelH Over a year ago

Could you please not post links without extracting the interesting part of it?

Duy Nguyen · Accepted Answer · 2016-12-06 09:22:30Z

1

If the line has a fixed pattern, you just have to get the part between "My Req Body" and "JSON". It's easy.

If the line does not have a fixed pattern, you can start with the first index of "{" and move forward to build the JSON string. You need to count for the number of open curly brackets and stop getting the string when you reach the same number of closed bracket. After having the string, you can use the library like gson to validate if it's a valid JSON string.

answered Dec 6, 2016 at 9:22

Duy Nguyen

5642 silver badges5 bronze badges

1 Comment

Priyanka Over a year ago

Thnkz Duy Nguyen.

Collectives™ on Stack Overflow

Extract Json String from Mixed String with JAVA

5 Answers 5

Comments

2 Comments

6 Comments

2 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

2 Comments

6 Comments

2 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related