How to Pretty Print JSON Using the Gson Library?

When working with JSON data in Java, it's often useful to format (or "pretty print") the JSON for better readability. The Gson library, developed by Google, is a popular choice for converting Java objects to and from JSON. Gson also provides a straightforward way to pretty print JSON.

In this blog post, we'll explore how to use Gson to pretty print JSON and make your JSON data more readable.

Why Pretty Print JSON?

JSON data is typically compact to save space, but this compact representation can be difficult to read, especially for debugging or documentation purposes. For example:

Compact JSON:

{"name":"Pavan Kumar Bhimavarapu","role":"SDET-QA","skills":["Java","Selenium","TestNG","Docker"]}

Pretty-Printed JSON:

{
  "name": "Pavan Kumar Bhimavarapu",
  "role": "SDET-QA",
  "skills": [
    "Java",
    "Selenium",
    "TestNG",
    "Docker"
  ]
}

Setting Up Gson in Your Project

Before we dive into the implementation, ensure you have Gson included in your project. If you're using Maven, add the following dependency to your pom.xml:

<dependency>

    <groupId>com.google.code.gson</groupId>

    <artifactId>gson</artifactId>

    <version>2.10</version>

</dependency>

For other build tools like Gradle, you can find the appropriate dependency here.

Pretty Printing with Gson

Gson provides a GsonBuilder class, which allows us to customize the behavior of Gson instances. To pretty print JSON, we use the setPrettyPrinting() method.

Here’s a simple example:

Example Code

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

import java.util.HashMap;
import java.util.Map;

public class PrettyPrintJsonExample {
    public static void main(String[] args) {
        // Sample data
        Map<String, Object> sampleData = new HashMap<>();
        sampleData.put("name", "Pavan Kumar Bhimavarapu");
        sampleData.put("role", "SDET-QA");
        sampleData.put("skills", new String[]{"Java", "Selenium", "TestNG", "Docker"});

        // Create a Gson instance with pretty printing enabled
        Gson gson = new GsonBuilder().setPrettyPrinting().create();

        // Convert the map to a pretty-printed JSON string
        String prettyJson = gson.toJson(sampleData);

        // Print the pretty JSON string
        System.out.println(prettyJson);
    }
}

Output

Running the above code will produce the following pretty-printed JSON output:

{

  "name": "Pavan Kumar Bhimavarapu",

  "role": "SDET-QA",

  "skills": [

    "Java",

    "Selenium",

    "TestNG",

    "Docker"

  ]

}

How It Works

  1. GsonBuilder: This is a builder for creating a Gson instance. Using this class, we can customize Gson’s behavior.
  2. setPrettyPrinting(): This method enables the pretty-printing feature in Gson, ensuring the generated JSON string is well-indented and formatted.
  3. toJson(): Converts a Java object (e.g., Map) to its JSON representation.

Additional Tips

  • File Output: You can write the pretty-printed JSON to a file using Java's I/O utilities:

try (FileWriter writer = new FileWriter("output.json")) {
    writer.write(prettyJson);
}

  • Nested Objects: Gson handles nested objects gracefully. Simply provide a complex object or nested map structure to toJson().

  • Custom Serialization: For more control over JSON formatting, Gson allows you to define custom serializers/deserializers.

When to Use Pretty Print?

  • Debugging: Helps in visualizing the structure of JSON data.
  • Logging: Makes JSON logs easier to interpret.
  • Documentation: Improves the presentation of JSON examples in documentation or APIs.

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