Map a JSON file to ENUM in Java

Introduction

Create a new project
Read a JSON file and property
Create an ENUM
Map the properties to a generic ENUM

Create a new project

Use the Maven starter

$ mvn archetype:generate -DgroupId=com.jsontoenum.app -DartifactId=json-to-enum -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -DinteractiveMode=false

Jump into the directory

$ cd json-to-enum/ && mvn package

Read a JSON file and property

The incredible com.typesafe.config

<dependency>
    <groupId>com.typesafe</groupId>
    <artifactId>config</artifactId>
    <version>1.3.4</version>
</dependency>

To be added to plugin.xml

<resources>
  <resource>
    <directory>src/resources</directory>
  </resource>
</resources>
<plugins>
  <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-shade-plugin</artifactId>
    <version>3.2.0</version>
    <executions>
      <execution>
        <phase>package</phase>
        <goals>
          <goal>shade</goal>
        </goals>
      </execution>
    </executions>
  </plugin>
</plugins>

New config in src/resources/application.json

{
  "swiss": {
    "cheese": "gruyere"
  }
}

Init and load the properties
Print our favorite type of cheese 🧀

package com.jsontoenum.app;

import com.typesafe.config.Config;
import com.typesafe.config.ConfigFactory;

public class App {
    public static void main(String[] args) {
        // Load and init the configuration library
        final Config conf = ConfigFactory.load();

        // Get the value of the JSON property
        final String cheese = conf.getString("swiss.cheese");

        System.out.println(String.format("I like %s 🧀", cheese));
    }
}

Compile and run

$ mvn package && java -cp target/json-to-enum-1.0-SNAPSHOT.jar com.jsontoenum.app.App

Create an ENUM

An ENUM to list a couple of Swiss cheese

package com.jsontoenum.app;

public enum Cheese {

   GRUYERE,
   TETE_DE_MOINE,
   CHAUX_DABEL,
   RACLETTE,
   VACHERIN,
   TOMME

}

Map the properties to a generic ENUM

A generic method to parse the properties

private static <E extends Enum<E>> E getEnumProperty(final Config conf, final String key, final Class<E> myClass) {
    // If no config loaded
    if (conf == null) {
        return null;
    }

    // If the config doesn't contains the key
    if (!conf.hasPath(key)) {
        return null;
    }

    // As previously, load the key value
    final String keyValue = conf.getString(key);

    // Does the property has a value
    if (keyValue == null || keyValue.isEmpty()) {
        return null;
    }

    // Map the property to the ENUM
    return Enum.valueOf(myClass, keyValue.toUpperCase());
}

The final test 🎉

public static void main(String[] args) {
    // Load and init the configuration library
   final Config conf = ConfigFactory.load();

   // Get the value of the JSON property
   final Cheese cheese =
                getEnumProperty(conf, "swiss.cheese", Cheese.class);

   if (Cheese.GRUYERE.equals(cheese)) {
       System.out.println(String.format("I really like %s 🧀", cheese));
   } else {
       System.out.println(String.format("%s is ok", cheese));
   }
}

Try to run our project

[INFO] ------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------
[INFO] Total time:  2.437 s
[INFO] Finished at: 2019-08-16T15:43:42+02:00
[INFO] ------------------------------------------------------------
I really like GRUYERE 🧀

Cherry on the cake 🍒🎂

Get the existing project

$ git clone https://github.com/peterpeterparker/json-to-enum.git

Author

David Dal Busco

Freelancer by day | Creator of DeckDeckGo by night

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