How to read multiple JSON files and write it to a single JSON file using java

I have multiple JSON file like below and want to merge the files and store the data from it into a new single json file as mentione below:

JSON1:

JSON2:

Expected O/P:

"jobRunID": "1940", "mappingResult": [ "studyID": "ca209-030", "fileName": "aesae.csv", "ref2FilePath": "C://stage/pra/cro/ca/209/030/ref2/aesae.csv", "columnName": "ae_start_dt", "currentMapping": "ae_start_dt,ae_st_dt", "isMapped": "N", "timeStamp": "20180827093033" , "studyID": "ca209-004", "fileName": "labressae.csv", "ref2FilePath": "C://stage/pra/cro/ca/209/030/ref2/labressae.csv", "columnName": "ae_verbatim", "currentMapping": "ae_vtm,ae_vt", "isMapped": "N", "timeStamp": "20180827093033" , "studyID": "ca209-030", "fileName": "aesae.csv", "ref2FilePath": "C://stage/pra/cro/ca/209/030/ref2/aesae.csv", "columnName": "ae_start_dt", "currentMapping": "ae_start_dt,ae_st_dt", "isMapped": "N", "timeStamp": "20180827093033" , "studyID": "ca209-004", "fileName": "labressae.csv", "ref2FilePath": "C://stage/pra/cro/ca/209/030/ref2/labressae.csv", "columnName": "ae_verbatim", "currentMapping": "ae_vtm,ae_vt", "isMapped": "N", "timeStamp": "20180827093033" ]

Any help will be appreciated as i am new handling JSON files in JAVA.
As per the above JOSNs for all the same JobID i want to merge the mappingResult from both the files in one o/p file as explained above in expected o/p.

I am trying with java by using below code but it read well for 2 input files but not sure how to di for multiple json file :

public class MergeJSON @JsonMerge List<Integer> contacts; public List<Integer> getContacts() return contacts; public void setContacts(List<Integer> contacts) this.contacts = contacts; @Override public String toString() return contacts.toString(); public static void main(String args) throws JsonProcessingException, IOException TypeReference<Map<String, MergeJSON>> type = new TypeReference<Map<String, MergeJSON>>() ; InputStream input = new ClassPathResource("C:\Users\sweta.h.sharma\Test.json").getInputStream(); InputStream input2 = new ClassPathResource("C:\Users\sweta.h.sharma\Test1.json").getInputStream(); ObjectMapper mapper = new ObjectMapper(); Object contacts = mapper.readValue(input, type); mapper.reader(type) .withValueToUpdate(contacts) .readValues(input2); System.out.println(contacts);

Hi, this question will be downvoted because you haven't included any details of your attempt to solve it - see stackoverflow.com/help/how-to-ask
– Joel Berkeley
Aug 29 at 10:43

1 Answer
1

Use Jackson Api.

Create Pojo class same as your json object (Class should have members like 'jobRunID','mappingResult').

//class JsonObj with getters & setters String jobRunID; List<Mappingresult> mappingResult; // Mappingresult is again POJO class with members like studyID,fileName etc

This are classes you have to use

com.fasterxml.jackson.core.JsonFactory; com.fasterxml.jackson.core.JsonParser; com.fasterxml.jackson.databind.ObjectMapper;

And Code.

ObjectMapper objMapper=new ObjectMapper(); JsonFactory jfactory = new JsonFactory(); JsonParser jParser1=jfactory.createJsonParser(jsonString1); //json String 1 JsonParser jParser2=jfactory.createJsonParser(jsonString2); //json String 2 JsonObj obj1=objMapper.readValue(jParser1,JsonObj.class);// JsonObj is Pojo for your jsonObject JsonObj obj2=objMapper.readValue(jParser2,JsonObj.class);

obj1 and obj2 will have list mappingResult as list. You can merge those list into one list and then can write in file or print on console

EDIT :

To get back the result as String, you can use ObjectMapper::writeValueAsString

obj1.getMappingResult().putAll(obj2.getMappingResult()); String jsonString = objMapper.writeValueAsString(obj1);

What is jsonString1 and jsonString2 ? Also if there are n no. of json file how it will work ?
– Shweta Sharma
Aug 29 at 12:14

@ShwetaSharma jsonString is Your Json text in form of String which you are reading from "C:\Users\sweta.h.sharma\Test.json"
– Tarun
Aug 29 at 12:47

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