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In this article we’ll be taking a look at how to read and write JSON files in Kotlin, specifically, using the Jackson library.
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"
}
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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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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JSON Google Extension
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Endpoint Example
http://maps.googleapis.com/maps/api/geocode/json?address=13+East+60th+Street+New+York,+NY
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#jsons #json arrays #json objects #what is json #jsons tutorial #blondiebytes
https://loizenai.com Programming Tutorial
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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.
Person(name:String,age:Int,messages:List)
Kotlin Object, then convert Person
object to JSON string/JSON file.
<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>
com.fasterxml.jackson.module.kotlin.*
More at:
https://grokonez.com/kotlin/kotlin-convert-object-tofrom-json-jackson-2-x
#kotlin #json #jackson
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JSON uses two types of brackets that are as follows:
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.
Let us see some reasons for why to choose JSON over XML:
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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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
#reading #writing #python #intermediate python tutorial #reading and writing to files in python