Write JSON Lines With Nested Data

Updated: Oct 16, 2022

This example shows you how to write JSON Lines with nested data using JsonLinesWriter.

This example is similar to Write JSON Lines, but for this case a JSON file with nested data is used.

This example can be easily modified to show how to Write Concatenated JSON With Nested Data.

JSON input

[
  {
    "id": "0001",
    "type": "donut",
    "name": "Cake",
    "ppu": 0.55,
    "batters":
    {
      "batter":
      [
        { "id": "1001", "type": "Regular" },
        { "id": "1002", "type": "Chocolate" },
        { "id": "1003", "type": "Blueberry" },
        { "id": "1004", "type": "Devil's Food" }
      ]
    },
    "topping":
    [
      { "id": "5001", "type": "None" },
      { "id": "5002", "type": "Glazed" },
      { "id": "5005", "type": "Sugar" },
      { "id": "5007", "type": "Powdered Sugar" },
      { "id": "5006", "type": "Chocolate with Sprinkles" },
      { "id": "5003", "type": "Chocolate" },
      { "id": "5004", "type": "Maple" }
    ]
  },
  {
    "id": "0002",
    "type": "donut",
    "name": "Raised",
    "ppu": 0.55,
    "batters":
    {
      "batter":
      [
        { "id": "1001", "type": "Regular" }
      ]
    },
    "topping":
    [
      { "id": "5001", "type": "None" },
      { "id": "5002", "type": "Glazed" },
      { "id": "5005", "type": "Sugar" },
      { "id": "5003", "type": "Chocolate" },
      { "id": "5004", "type": "Maple" }
    ]
  }
]

Java Code Listing

package com.northconcepts.datapipeline.examples.cookbook;

import com.northconcepts.datapipeline.core.DataReader;
import com.northconcepts.datapipeline.core.DataWriter;
import com.northconcepts.datapipeline.job.Job;
import com.northconcepts.datapipeline.json.JsonRecordReader;
import com.northconcepts.datapipeline.json.JsonLinesWriter;

import java.io.File;

public class WriteJsonLinesWithNestedData {
    public static void main(String[] args) {
        DataReader reader = new JsonRecordReader(new File("data/input/nested-data.json"))
                .addRecordBreak("/array/object");

        DataWriter writer = new JsonLinesWriter(new File("data/output/json-lines-with-nested-data.jsonl"));

        Job.run(reader, writer);
    }
}

Code Walkthrough

  1. JsonRecordReader is created corresponding to the input file nested-data.json.
  2. .addRecordBreak() method is used to separate the records. /array/object specify the path to the record you want to read. To see the paths to the records run the code in debug mode i.e .setDebug(true), it is false by default.
  3. The JsonLinesWriter object is created to produce the json-lines-with-nested-data.jsonl output file.
  4. Data is then transferred from the reader to the output file via Job.run().

JsonRecordReader

JsonRecordReader is an input reader that can read records from an input JSON stream. A method JsonRecordReader.addRecordBreak tells the reader to return a new record using whatever fields have been assigned. This method is basically used to demarcate records.

Output

{"id":"0001","type":"donut","name":"Cake","ppu":0.55,"batters":{"batter":[{"id":"1001","type":"Regular"},{"id":"1002","type":"Chocolate"},{"id":"1003","type":"Blueberry"},{"id":"1004","type":"Devil's Food"}]},"topping":[{"id":"5001","type":"None"},{"id":"5002","type":"Glazed"},{"id":"5005","type":"Sugar"},{"id":"5007","type":"Powdered Sugar"},{"id":"5006","type":"Chocolate with Sprinkles"},{"id":"5003","type":"Chocolate"},{"id":"5004","type":"Maple"}]}
{"id":"0002","type":"donut","name":"Raised","ppu":0.55,"batters":{"batter":[{"id":"1001","type":"Regular"}]},"topping":[{"id":"5001","type":"None"},{"id":"5002","type":"Glazed"},{"id":"5005","type":"Sugar"},{"id":"5003","type":"Chocolate"},{"id":"5004","type":"Maple"}]}

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