Providing a JsonFormat for a Sequence of Objects

Providing a JsonFormat for a Sequence of Objects

By : Fayssal Fellah
Date : November 17 2020, 08:25 AM
This might help you Look at the source of spray.json.CollectionFormats.
Here is a runnable implementation:
code :
import spray.json._

class Adress(val streetname: String, val plz: BigDecimal, val city: String)

class Person(val name: String, val adresses: Seq[Adress])

object PersonJsonProtocol extends DefaultJsonProtocol {
  implicit object AdressJsonFormat extends RootJsonFormat[Adress] {
    def write(addr: Adress) = JsObject(Map(
      "streetname" -> JsString(addr.streetname),
      "plz" -> JsNumber(addr.plz),
      "city" -> JsString(addr.city)
    def read(value: JsValue): Adress = ???
  implicit object PersonJsonFormat extends RootJsonFormat[Person] {
    def write(pers: Person) = JsObject(Map(
      "name" -> JsString(pers.name),
      "adresses" -> JsArray(pers.adresses.map(_.toJson).toList)
    def read(value: JsValue): Person = ???

object Main extends App {
  import PersonJsonProtocol._
  val person = new Person("joe", Seq(new Adress("street", 123, "city")))
  println("poso's default toString: %s".format(person))
  val personJVal = person.toJson
  println("JValue's toString: %s".format(personJVal))
  val personJson = personJVal.prettyPrint
  println("pretty-printing: %s".format(personJson))
poso's default toString: Person@680ccad
JValue's toString: {"name":"joe","adresses":[{"streetname":"street","plz":123,"city":"city"}]}
pretty-printing: {
  "name": "joe",
  "adresses": [{
    "streetname": "street",
    "plz": 123,
    "city": "city"

Share : facebook icon twitter icon
Compression of sequence of integers providing random access

Compression of sequence of integers providing random access

By : Walter
Date : March 29 2020, 07:55 AM
Hope this helps If all your integers have the same frequency, then a fair approximation to optimal compression will be ceil(log2(k)) bits per integer. You can access a bit-array of these in constant time.
If k is painfully small (like 3), the above method may waste a fair amount of space. But, you can combine a fixed number of your small integers into a base-k number, which can fit more efficiently into a fixed number of bits (you may also be able to fit the result conveniently into a standard-sized word). In any case, you can also access this coding in constant time.
code :
log2( n!/(f!)^k ) = log2(n!) - k * log2(f!)
~ n log2(n) - n log2(e) - k ( f log2(f) - f log2(e) )
= n log2(n) - n log2(e) - n log2(f) + n log2(e)
= n ( log2(n) - log2(f) )
= n log2(n/f)
= n log2(k)
Turn sequence of objects with collection into a flat sequence

Turn sequence of objects with collection into a flat sequence

By : diana alejandra Hinc
Date : March 29 2020, 07:55 AM
To fix the issue you can do You're looking for this overload of Observable.SelectMany. This takes a projection function that returns an IEnumerable.
code :
public IObservable<B> C
    get { return _sequence.SelectMany(o => o.Collection); }
Random Name Generator providing same name to multiple objects

Random Name Generator providing same name to multiple objects

By : Erik
Date : March 29 2020, 07:55 AM
wish helps you I'll supose placing the NameGenerator nameGen = new NameGenerator(); statement in the day function of World outsite the for loop will solve you're problem.
code :
NameGenerator nameGen = new NameGenerator();
for (int i = 0; i < 100; i++)
   Human h = new Human(nameGen.generateName(4, 8), nameGen.generateName(4, 12));
Providing a Sequence as a parameter to a method accepting varargs

Providing a Sequence as a parameter to a method accepting varargs

By : Parillah Latea
Date : March 29 2020, 07:55 AM
This might help you In the Spark DataFrame we have a select method that has a varargs second parameter: , You should wrap String to column:
code :
 Df.select(cols.map(x => col(x)) :_*)
Deserializing a json which contains @JsonFormat(shape=JsonFormat.Shape.ARRAY) and custom object using jackson

Deserializing a json which contains @JsonFormat(shape=JsonFormat.Shape.ARRAY) and custom object using jackson

By : Nisha
Date : March 29 2020, 07:55 AM
it fixes the issue JsonFormat does the trick but you also need to declare constructor with JsonCreator annotation. Take a look on below example:
code :
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.File;
import java.util.List;

public class JsonApp {

    public static void main(String[] args) throws Exception {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();

        ObjectMapper mapper = new ObjectMapper();
        Response myPojo = mapper.readValue(jsonFile, Response.class);

class Response {

    private List<Value> values;

    public List<Value> getValues() {
        return values;

    public void setValues(List<Value> values) {
        this.values = values;

    public String toString() {
        return "Response{" +
                "values=" + values +

@JsonFormat(shape = JsonFormat.Shape.ARRAY)
class Value {

    private long timestamp;
    private float val;

    public Value(@JsonProperty("timestamp") long timestamp, @JsonProperty("val") float val) {
        this.timestamp = timestamp;
        this.val = val;

    public long getTimestamp() {
        return timestamp;

    public void setTimestamp(long timestamp) {
        this.timestamp = timestamp;

    public float getVal() {
        return val;

    public void setVal(float val) {
        this.val = val;

    public String toString() {
        return "Value{" +
                "timestamp=" + timestamp +
                ", val=" + val +
  "values": [
Response{values=[Value{timestamp=1552215648, val=18.0}, Value{timestamp=123, val=12.24}]}
Related Posts Related Posts :
  • how to write r.headers from different urls into one json?
  • Parsing JSON concurrently - panic of runtime error (decoding related)
  • How to fix "Subscript out of range" error in XML HTTP Request
  • Splitting nested arrays as separate entities
  • Trying to parse the JSON and create an extracted JSON
  • NiFi JoltTransformJson outputs only first record
  • Dynamic (But known as another key value) JSON Decoding with Swift Decodable
  • How to use map on json response returned by a REST API with ReactJs
  • How to read a file line by line and then output all lines compounded with sth in jq?
  • java.lang.RuntimeException: Failed : HTTP error code : 400 : Bad Request
  • How to check jq result is null or not?
  • CloudFormation - How to use Sub intrinsic function?
  • VBA: Nested JSON Object Structure for UK Bank Holidays - Run Time Errors 13, 438 and 449
  • JasperReports. Using value from parent json in child table
  • Output key value pairs as JSON from T-SQL query
  • Getting key value pairs with linux server
  • Modifying settings.json in vscode to add shell escape flag to pdflatex in latex workshop
  • Unable to render data into grid column using JSON results
  • JSON decode failed
  • How to remove brakets on Json respone
  • How to parse JSON-input
  • JSON syntax for getting personal query ID
  • detecting 400 response without JSON response
  • Newtonsoft deserializing Json incorrectly
  • Getting _jsonparsefailure with valid json in logstash
  • How to send Map as String in POST request in flutter?
  • Difficulty fetching json data from API using Angular
  • Reading JSON data for my select query in SQL Server
  • AWS CloudFormation Template (JSON) to Create EC2 - Unexpected Error
  • How to concat multiple fields to same line with jq
  • Issue sending POST request from Swift
  • Storing JSON in BigQuery
  • How to get the value of a key in a JSON?
  • How to validate JSON input in Go
  • Extracting specific and latest data from http webserver using golang
  • Incorrect type. Expected "object"
  • json_to_record with embedded encoded json in PostgreSQL >= 10
  • Nested json extract from powershell
  • Parsing Json using Golang
  • Type 'number' is not assignable to type 'string'. How to cast number to string
  • kubectl - format the resource quota values in json format
  • Initializing and inserting nested JSON data in Golang?
  • Open JSON files in PhpStorm built-in web server
  • Extract Badge ID from JSON in .gitlab-ci.yml
  • Sharing Json Schema files among projects with versioning
  • Export Json data to an excel file using Angular 4
  • Return an empty array instead of null with golang for json return with gin
  • can Kafka connect value conveter (JSONConverter) can be used to convert GPB?
  • read json and access multiple keys
  • Spark How to get number of Keys changed in two JSONS in Scala?
  • Break JSON in pager "less"
  • How to filter Map in Flutter?
  • Convert hashmap to simple object in Groovy
  • Not extracting json properly using json4s
  • How do I display JSON data in my tableView when objects have the same value?
  • Where I can parse IoT data in Azure so I can afterwards save it to SQL DB
  • How to unmarshal this json string
  • What's wrong with my JSON?
  • JSON parsing problem in BlackBerry
  • GWT: How can I use JsonpRequestBuilder to handle a Json response of a list
  • shadow
    Privacy Policy - Terms - Contact Us © festivalmusicasacra.org