How to read the JSON line and make it into a Java/Kotlin code

Question

I am making a project to get an API using Retrofit, in order to get the data from the website, I have to understand that there is some data stored into multiple data within the JSON, such as this:

launches [{
   id*  string
   provider string
}]

What I want from the JSON code is to convert it into a Java/Kotlin code for the small project, If someone can able to explain to me OR show it to me in a Java/Kotlin code on how to make the setter/getter sequence on this code. Thank you for your time.

Here is the full example JSON format:

Article{
    id integer
    featured boolean
    default: false
    title   string
    url string
    imageUrl string
    newsSite string
    summary string
    publishedAt string
    launches [{
        id* string
        provider string
    }]
    events [{
        id* string
        provider string
    }]
}

This one actually json :

{
"employee":{"name":"John", "age":30, "city":"New York"}
}

I'm not sure what you have there. It is neither JSON nor JSON Schema. Where did this come from? — stdunbar, Dec 02 '21 at 15:52
@stdunbar https://api.spaceflightnewsapi.net/v3/documentation#/ comes from this link and it's a Schema yes. — Georgi Tasev, Dec 02 '21 at 15:53
No, that is Swagger's "schema". It is not JSON. See [this post](https://stackoverflow.com/questions/53169992/how-to-generate-java-code-from-the-swagger-2-0-swagger-codegen-cli-jar) for more info. — stdunbar, Dec 02 '21 at 15:59

score 1 · Answer 1 · answered Dec 02 '21 at 16:24

What you are looking for is JSON Parsing Libraries or JSON Converters for Retrofit.

You see Retrofit does not have a built-in JSON converter to parse from JSON string to Java or Kotlin objects. Instead, Retrofit ships support for Moshi, Jackson or GSON etc.

Converters like Moshi are JSON parsers that convert a JSON string into Kotlin objects or vice-versa.

These converters are specified on the Retrofit.Builder. You also need to add the converters' dependencies alongside that of Retrofit to your project.

/*using MoshiBuilder to create MoshiObject i.e. the
JSON-String-to-Kotlin-Object converter*/

/*For Moshi's annotations to work properly with Kotlin
add the KotlinJsonAdapterFactory*/

private val moshi = Moshi.Builder()
    .add(KotlinJsonAdapterFactory())
    .build()


//using Retrofit Builder to create Retrofit Object
private val retrofit = Retrofit.Builder()
    .addConverterFactory(MoshiConverterFactory.create(moshi)) //handles JSON
    .baseUrl(BASE_URL)
    .build()

There is a plugin called JsonToKotlinClass which you can use to copy the JSON string from your REST API and paste it on the plugin to generate a Kotlin Object for you.

I would advise you to watch video courses on how to go about the whole thing. For Example watch this course.

Atharva Shivankar · Answer 2 · 2021-12-03T15:19:09.300

Java and Kotlin can use Google's GSON library that lets you convert Plain Old Java Objects (POJOs) to and from a JSON string. Also, as someone pointed out, what you have posted looks like incorrect syntax for the JSON schema. Please make sure it adheres to the schema. First, add the GSON dependency in your pom.xml (or its equivalent in Kotlin, if different. Sorry, I'm a Java programmer).

Dependency:

<dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.8.9</version>
</dependency>

This is how you can use GSON -

Create an Article class in Java/Kotlin. This class will be your blueprint for creating objects.
Instantiate a GSON object in the class where you have the JSON string.

Gson gson = new Gson();

Instantiate a new object and map the JSON string to POJO using GSON.

String exampleJson = "{"Article":{ "id":123, "featured": true, etc... }}";
Article myArticleObj = gson.fromJson(exampleJson, Article.class);

You can use gson.toJson(Object) for the reverse conversion to a JSON string.

And that's it! Hope it helped!

How to read the JSON line and make it into a Java/Kotlin code

2 Answers2