Reading and Writing JSON in Kotlin with Jackson

In this article we’ll be taking a look at how to read and write JSON files in Kotlin, specifically, using the Jackson library.

Jackson Dependency

To utilize Jackson, we’ll want to add its jackson-module-kotlin dependency to our project. If you’re using Maven, you can simply add:

<dependency>
    <groupId>com.fasterxml.jackson.module</groupId>
    <artifactId>jackson-module-kotlin</artifactId>
    <version>2.12.1</version>
</dependency>

Or, if you’re using Gradle, you can add:

implementation 'com.fasterxml.jackson.module:jackson-module-kotlin:2.12.1'

With the dependency in place, let’s define a JSON object we’ll want to read:

{
   "id":101,
   "username":"admin",
   "password":"Admin123",
   "fullName":"Best Admin"
}

Reading a JSON Object to Kotlin Object

Let’s take a look at how we can deserialize a JSON object into a Kotlin object. Since we’ll want to convert the JSON contents into a Kotlin object, let’s define a User data class:

data class User (
    val id: Int,
    val username: String,
    val password: String,
    val fullName: String
)

Then, we’ll want to instantiate the object mapper, which can easily be done with:

import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper

// Registering the Kotlin module with the ObjectMpper instance
val mapper = jacksonObjectMapper()

// JSON String
val jsonString = """{
    "id":101,
    "username":"admin",
    "password":"Admin123",
    "fullName":"Best Admin"
    }"""

With that done, we can pass JSON contents into our ObjectMapper methods, such as readValue(), as usual for Jackson:

// Read data from a JSON string
val userFromJson = mapper.readValue<User>(jsonString)
// Or
val userFromJsonWithType: User = mapper.readValue(jsonString)

If we print the value of userFromJson we’ll see something like this:

User(id=101, username=admin, password=Admin123, fullName=Best Admin)

The readValue() function can be used with or without the Class parameter, as you saw a little earlier with the two variables (userFromJson and userFromJsonWithType).

Note: Using the function without the Class parameter will materialize the type and automatically create a TypeReference for Jackson.

#kotlin

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What is JSON? | JSON Objects and JSON Arrays | Working with JSONs Tutorial

In this video, we work with JSONs, which are a common data format for most web services (i.e. APIs). Thank you for watching and happy coding!

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What is an API?
https://youtu.be/T74OdSCBJfw

JSON Google Extension
https://chrome.google.com/webstore/detail/json-formatter/bcjindcccaagfpapjjmafapmmgkkhgoa?hl=en

Endpoint Example
http://maps.googleapis.com/maps/api/geocode/json?address=13+East+60th+Street+New+York,+NY

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Kotlin - Convert Object to/from JSON with Jackson 2.x » grokonez

https://grokonez.com/kotlin/kotlin-convert-object-tofrom-json-jackson-2-x

Kotlin – Convert Object to/from JSON with Jackson 2.x

This tutorial shows you how to use Jackson 2.x to convert Kotlin object to/from JSON.

I. Technology

- Java 1.8 - Kotlin 1.1.2 - Maven 3.5.1

II. Overview

1. Goal

Convert JSON string/JSON file/JSON url to Person(name:String,age:Int,messages:List) Kotlin Object, then convert Person object to JSON string/JSON file.

2. Steps to do

- add Dependency:

<dependency>
	<groupId>org.jetbrains.kotlin</groupId>
	<artifactId>kotlin-stdlib</artifactId>
	<version>1.1.2</version>
</dependency>
<dependency>

<groupId>com.fasterxml.jackson.module</groupId>

<artifactId>jackson-module-kotlin</artifactId>

<version>2.8.8</version>

</dependency>

• import com.fasterxml.jackson.module.kotlin.*
• use ObjectMapper instance:

More at:

https://grokonez.com/kotlin/kotlin-convert-object-tofrom-json-jackson-2-x

#kotlin #json #jackson

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JSON Parsing in Android - Step by Step Implementation

JSON Structures in Android

JSON uses two types of brackets that are as follows:

• [] – To declare the elements of Array in JSON, they’re written in square brackets.
• {} – To create JSON objects, the elements are written in curly brackets.

JSON has the following types of structures that are:

1. JSON Objects

The elements inside the curly brackets are known as Objects.

2. JSON Array

A list of values, known as Arrays.

3. JSON Key-Value

This data is stored as a pair of keys and values. Here the keys can be a name, a number for which the values can be Seema, 98767586 etc.

Why JSON Parsing in Android over XML?

Let us see some reasons for why to choose JSON over XML:

• It is much easier and quicker with high performance
• It can use arrays
• Its libraries do not depend on other libraries
• The codes written in JSON are short, clean and easy to understand
• It is free to open use and open-source tool
• In JSON value retrieval is easy
• It has a fully automated way of serializing/deserializing JavaScript.
• It is supported by many Ajax toolkits and most of the backend technologies.

Examples of XML and JSON

Let us see the code difference of JSON and XML files:

XML Example:

<?xml version= “1.0” encoding= “” ?>
<student>
        <student>
  <name> Sia Sharma</name>
  <city> Chandigarh</city>
         </student>
        <student>
  <name>Dimple D’souza</name>
  <city> Nagpur</city>
         </student>
      <student>
  <name>Anna Jones</name>
  <city> Mumbai</city>
         </student>
  </student>

JSON Example:

{ “students”: [
{ “name”: “Sia Sharma”, “city”: “Chandigarh”},
{ “name”: “Prachi D’Souza”, “city”: “Nagpur”},
{ “name”: “Annas Jones”, “city”: “Mumbai”}
]}

I hope the difference is all clear in front of you. This is how simple JSON is and how easily it could be understood.

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Reading and Writing to Files in Python - Intermediate Python Tutorial #2

In this Python tutorial, we will learn how to deal with text files in Python using the built-in open function. You will understand how to use the most important modes: read, write and append.
That’s not all! We will discuss about file parsing and touch important string methods used for that such as: strip( ) and split( ). Finally we wrap up with a parsing file exercise to practice the new concepts. After that video you will be confident to deal with text files which is a very important skill to have as a programmer.

Playlist: Intermediate Python Tutorials | Video #2
Access the codes here: https://github.com/rscorrea1/youtube.git

Timestamp:
00:00 - Summary of the video
00:17 - Types of files
00:43 - How to open a file
01:17 - File modes
02:15 - How to read data from a file
03:00 - with statement
04:10 - readlines( ) method
05:05 - String: strip( ) method
06:22 - How to iterate over a file line by lin
08:47 - How to write data to a file
11:43 - How to append data to a file
12:37 - Exercise: Parsing a text file
16:14 - Converting data types
17:00 - Next video announcement

Thumbnail:
Photo by Mario Ho on Unsplash

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