How do I parse JSON objects from a JSONArray?

Question

I have a very large JSON file in the following format:

[{\"fullname\": \"name1\", \"id\": \"123\"}, {\"fullname\": \"name2\", \"id\": \"245\"}, {\"fullname\": \         


        

Answer 1

you can use Json.simple java api , below is code that can helpful to you

        byte[] bFile = Files.readAllBytes(new File("C:/xyz.json").toPath());
        JSONArray root = (JSONArray) JSONValue.parseWithException(bFile);
        JSONObject rootObj = (JSONObject) root.get(0);

You can get values from JSONObject based on key , it also depends on format of your json as there could be nested json data. So you have to extract data accordingly . Apart from this you can use jackson parser api or GSON as well.

Answer 2

Make your life easy and use an ObjectMapper. This way you simply define a Pojo with the same properties as you json object.

In you case you need a Pojo that looks like this:

public class Person{
    private String fullname;
    private int id;

    public Person(String fullname, int id) {
        this.fullname = fullname;
        this.id = id;
    }

    public String getFullname() {
        return fullname;
    }

    public int getId() {
        return id;
    }
}

With that you only need to do:

ObjectMapper objectMapper = new ObjectMapper();
List<Person> persons = objectMapper.readValue(myInputStream, TypeFactory.defaultInstance().constructCollectionType(List.class, Person.class));

This is a hassle free and type safe approach.

Dependencies needed:

https://github.com/FasterXML/jackson-databind

<dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
</dependency>

Answer 3

Okay folks...just solved my problem. I am posting the solution in case someone runs into the same issue again, can use my solution. My solution is partly motivated by Rahul Rabhadiya. Thanks, dude.

try{
 row=br.readLine();
            JSONArray root = (JSONArray) JSONValue.parseWithException(row);

            for (int i=0;i<root.size();i++)
            {

            JSONObject rootObj = (JSONObject) root.get(i);
            String fullname=(String) rootObj.get("fullname");

            System.out.println (fullname);
            }
    }catch(Exception e)
         {
        e.printStackTrace();
        }

Answer 4

I would suggest going with Jackson, in particular the Jackson Streaming API which is perfect for parsing large arrays like this.

See this answer: https://stackoverflow.com/a/24838392/3765428

Answer 5

Your json is a JSONArray, so when you are parsing it, you need to parse it as a JSONArray.

        JSONParser jsonParser = new JSONParser();
        JSONArray a = (JSONArray) jsonParser.parse(new FileReader(src));
        for (Object o : a) {
            // access your object here. 
        }