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Convert JSON To Lower_case_with_underscores Using Gson

8 min read 11-15- 2024
Convert JSON To Lower_case_with_underscores Using Gson

Table of Contents :

To convert JSON keys to a lower_case_with_underscores format using Gson, you can leverage the flexibility of Gson’s JsonSerializer and JsonDeserializer interfaces. This article will guide you through the process, detailing key concepts and providing clear examples. Additionally, we will cover how to handle both serialization and deserialization effectively while maintaining clean and readable code. Let's dive in!

Understanding the Basics of JSON

JSON (JavaScript Object Notation) is a lightweight format for data interchange. It is easy for humans to read and write and easy for machines to parse and generate. JSON's structure is built on two primary data types:

  1. Objects: An unordered collection of key/value pairs.
  2. Arrays: An ordered collection of values.

When working with JSON in Java, the Gson library simplifies the process of converting Java objects to JSON and vice versa.

Why Use lower_case_with_underscores Format?

The lower_case_with_underscores format (also known as snake_case) is commonly used in various programming languages, particularly in the Python community and databases like PostgreSQL. This format enhances readability and prevents naming conflicts, especially when the keys contain uppercase letters or special characters.

Setting Up Gson

To begin using Gson in your project, you'll need to add the Gson dependency to your build tool. If you’re using Maven, include the following in your pom.xml:


    com.google.code.gson
    gson
    2.10.1

For Gradle, include this in your build.gradle file:

implementation 'com.google.code.gson:gson:2.10.1' // Check for the latest version

Converting JSON Keys to lower_case_with_underscores

Step 1: Create a Custom Gson Serializer

The first step is to implement a custom serializer to convert JSON keys to lower_case_with_underscores. Here’s a sample serializer implementation:

import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

import java.lang.reflect.Type;

public class SnakeCaseSerializer implements JsonSerializer {
    
    @Override
    public JsonElement serialize(Object src, Type typeOfSrc, JsonSerializationContext context) {
        JsonObject jsonObject = context.serialize(src).getAsJsonObject();
        JsonObject newJsonObject = new JsonObject();
        
        for (String key : jsonObject.keySet()) {
            String snakeCaseKey = toSnakeCase(key);
            newJsonObject.add(snakeCaseKey, jsonObject.get(key));
        }
        
        return newJsonObject;
    }

    private String toSnakeCase(String input) {
        // Using regex to convert camelCase to lower_case_with_underscores
        return input.replaceAll("([a-z])([A-Z])", "$1_$2").toLowerCase();
    }
}


Step 2: Create a Custom Gson Deserializer


Next, we need to implement a deserializer to convert JSON keys back to their original format. This is essential for deserializing JSON data into Java objects:


import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;

import java.lang.reflect.Type;

public class SnakeCaseDeserializer implements JsonDeserializer {
    
    @Override
    public T deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) {
        JsonObject jsonObject = json.getAsJsonObject();
        JsonObject newJsonObject = new JsonObject();

        for (String key : jsonObject.keySet()) {
            String originalKey = toOriginalCase(key);
            newJsonObject.add(originalKey, jsonObject.get(key));
        }
        
        return context.deserialize(newJsonObject, typeOfT);
    }

    private String toOriginalCase(String input) {
        // This conversion is a bit trickier; ensure your original keys are in a consistent format
        return input.replaceAll("(_[a-z])", match -> match.group(1).toUpperCase().replace("_", ""));
    }
}



Step 3: Register the Custom Serializers with Gson


To use your custom serializers, create a Gson instance with your serializers registered:


import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

public class GsonUtil {
    public static Gson createGson() {
        return new GsonBuilder()
                .registerTypeAdapter(Object.class, new SnakeCaseSerializer())
                .registerTypeAdapter(Object.class, new SnakeCaseDeserializer<>())
                .create();
    }
}



Example Usage


Defining a Java Class


Here’s a simple example of a Java class we’ll convert to JSON:


public class Person {
    private String firstName;
    private String lastName;
    private int age;

    // Getters and Setters
    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}



Serializing the Java Object to JSON


Now, let’s serialize a Person object to JSON:


public class Main {
    public static void main(String[] args) {
        Gson gson = GsonUtil.createGson();
        
        Person person = new Person();
        person.setFirstName("John");
        person.setLastName("Doe");
        person.setAge(30);

        String json = gson.toJson(person);
        System.out.println(json); // {"first_name":"John","last_name":"Doe","age":30}
    }
}



Deserializing JSON back to Java Object


You can also deserialize JSON strings back into Java objects using the custom deserializer:


public class Main {
    public static void main(String[] args) {
        Gson gson = GsonUtil.createGson();

        String json = "{\"first_name\":\"John\",\"last_name\":\"Doe\",\"age\":30}";
        Person person = gson.fromJson(json, Person.class);
        
        System.out.println(person.getFirstName()); // John
        System.out.println(person.getLastName());  // Doe
        System.out.println(person.getAge());        // 30
    }
}



Important Notes




Ensure your keys are consistently formatted in your original objects and when converting back from JSON to Java. The toOriginalCase method must match the naming conventions you use in your Java classes.






Performance Considerations: Using custom serializers and deserializers can introduce overhead, especially with large objects. Always test performance in your specific context.




Summary


In this article, we've explored how to convert JSON keys to the lower_case_with_underscores format using the Gson library. We created custom serializers and deserializers to handle both directions of conversion smoothly. The flexibility of Gson allows you to tailor JSON processing according to your application's needs, thus improving interoperability with other systems and languages.


By applying these techniques, you can ensure that your JSON data is in a consistent and readable format, making it easier to work with across different layers of your application.


                                          
                                       
                                    
                                 
                              
                           
                        
                     
                     

                        

                     

                  
                  

                     

                        

                           
                        

                     

                  

                  

                  
                  
                  

                     

                        
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