How to Parse JSON in Java?

Parsing JSON in Java sounds simple until you are confused about choosing between Jackson, Gson, org.json, JSON.simple, or JSON-P. Which one is right for your project? How do you handle nested JSON or map it to a Java object cleanly? If you have ever felt unsure or copied code without truly understanding it, this guide is for you.

In this blog, learn how to parse JSON in Java with clear examples, simple explanations, and all the tools you need.

Table of Contents:

• What is JSON?
• Why Parse JSON in Java?
• How to Parse JSON in Java
  • Parsing JSON from a String
  • Parsing JSON from an Array
  • Parsing JSON from a File by Creating POJO
  • Parsing JSON from Object
  • Parsing JSON from an API Using RestAssured’s Native Parsing
• Parsing JSON Libraries in Java
  • org.json
  • Jackson
  • Gson by Google
  • JSON.simple
  • JSON-P (Java API for JSON Processing)
• JSON Parsing Libraries Comparison in Java
• Conclusion

What is JSON?

JSON (JavaScript Object Notation) is a lightweight format for storing and transporting data. It is used for transporting data from the server to the web. It is easy to read and write, and is also easy for machines to parse and generate. It represents data in the form of key-value pairs or arrays.

Example:

{
  "id": 101,
  "name": "Intellipaat",
  "email": "[email protected]",
  "isActive": true,
  "roles": ["user", "admin"],
  "address": {
    "city": "Bareilly",
    "zip": "1234x"
  }
}

where,

• Objects are enclosed in {} and made up of key-value pairs.
• Arrays are enclosed in [] and are used to hold lists.
• Keys are always strings (in double quotes).
• Values can be strings, numbers, booleans, arrays, objects, or null.

Why Parse JSON in Java?

In modern Java applications, like Microservices, that use the API for the transfer of data between web pages, the data is exchanged in the form of JSON. Java does not natively understand the JSON format. Hence, parsing JSON means converting the raw JSON into JAVA objects so that the communication between the websites can be easy and fast.

Let us understand how we can parse the JSON object in Java using different methods and libraries.

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How to Parse JSON in Java

1. Parsing JSON from a String

JsonParser is a class in the Gson library (com.google.gson) that helps parse JSON text into JsonElement objects for further processing.  While useful, many developers today prefer higher-level parsing methods like Gson.fromJson() or Jackson’s ObjectMapper.

The parsing can be done from the string. Below is an example of it.

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following gson dependency in the pom.xml file.

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.10.1</version>
</dependency>

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file

Step 4: Here is your Java file.

Step 5: Run the file.

Output:

2. Parsing JSON from an Array

JSON often contains arrays, and this data can also be parsed from the array.

Example:

Output:

Explanation: This program helps to read a JSON array and print each person’s name and age. It changes the JSON text into a JSONArray, then picks each object and shows its values. It can run on any Java compiler with the org.json library.

3. Parsing JSON from a File by Creating POJO

In the real world, the data not only comes with strings, but it also comes in the form of files.

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following Jackson dependency to your pom.xml file to use the ObjectMapper class for parsing JSON into Java POJOs

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.16.1</version>
</dependency>

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file

Step 4: Create user.json.

{
  "userId": 1,
  "name": "Ali"
}

Step 5: Create the POJO

Step 6: Create the Main file.

Step 7: Run the file.

Output:

Note: Files should be in the src/main/resources folder to ensure they are loaded properly.

4. Parsing JSON Object in Java

To parse a JSONObject in Java, you can use libraries such as Jackson or Gson, as mentioned above.

Here is an example of it by using the Jackson library.

Add the following Maven dependencies in the pom.xml file.

<dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.16.0</version>
</dependency>

Example:

Note: In real projects, POJOs are placed in separate files for better structure.

Output:

5. Parsing JSON from an API Using RestAssured’s Native Parsing

RestAssured supports automatic JSON parsing via its built-in JSONPath and integrates with Jackson/Gson as needed. It is a popular Java library used for testing RESTful web services. It has automatic response parsing, i.e., it can deserialise HTTP response bodies (JSON and XML) into Java objects.

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following Jackson dependency in the pom.xml file.

<dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.17.0</version>
        </dependency>

<dependency>
            <groupId>io.rest-assured</groupId>
            <artifactId>rest-assured</artifactId>
            <version>5.4.0</version>
</dependency>

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file

Step 4: Here is your Java file.

Note: In real projects, POJOs are placed in separate files for better structure.

Step 5: Run the file.

Output:

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Parsing JSON Libraries in Java

1. org.json

The org.json library provides a simple way to parse and create JSON in Java. It can also convert between JSON, XML, HTTP Headers, Cookies, Comma Delimited List or Text, etc.

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following org.json dependency in the pom.xml file.

<dependency>
  <groupId>org.json</groupId>
  <artifactId>json</artifactId>
  <version>20231013</version>
</dependency>

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file.

Step 4: Here is your Java file.

Step 5: Run the file.

Output:

2. Jackson

Jackson is a high-performance JSON processor for Java. It can read JSON as a tree (like DOM for XML) and can also work with JSON in a streaming manner. It can handle complex data structures and large JSON files.

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following Jackson dependency in the pom.xml file.

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.16.0</version>
</dependency>

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file

Step 4: Here is your Java file.

Step 5: Run the file.

Output:

3. Gson by Google

Gson is a Java library developed by Google for converting Java objects to JSON and vice versa. It can also be used to convert a JSON string to a Java object. It is simple and lightweight.  It parses JSON without using a big or complex library.

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following Gson dependency in the pom.xml file.

<dependency>
  <groupId>com.google.code.gson</groupId>
  <artifactId>gson</artifactId>
  <version>2.10.1</version>
</dependency>

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file

Step 4: Here is your Java file.

Step 5: Run the file.

Output:

4. JSON.simple

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following json.simple dependency in the pom.xml file for the Maven project.

<dependency>
    <groupId>com.googlecode.json-simple</groupId>
    <artifactId>json-simple</artifactId>
    <version>1.1.1</version>
</dependency>

For Gradle, add the following to your build.gradle file.

implementation 'com.googlecode.json-simple:json-simple:1.1.1'

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file. For Gradle, reload the project to install all the dependencies in the project.

Step 4: Here is your Java file.

Step 5: Run the file.

Output:

5. JSON-P (Java API for JSON Processing)

JSON-P is a standard API to parse JSON and object models. It is not as popular as Gson or Jackson, but it is a part of the standard Java EE API.

Step 1: Create a Maven project using IntelliJ or any other IDE.

Step 2: Add the following json.simple dependency in the pom.xml file for the Maven project.

<dependencies>
        <dependency>
            <groupId>jakarta.json</groupId>
            <artifactId>jakarta.json-api</artifactId>
            <version>2.1.1</version>
        </dependency>
        <dependency>
            <groupId>org.eclipse.parsson</groupId>
            <artifactId>parsson</artifactId>
            <version>1.1.1</version>
        </dependency>
    </dependencies>

Step 3: Run the Maven clean and package command that will install all the dependencies from the pom.xml file.

Step 4: Here is your Java file.

Step 5: Run the file.

Output:

JSON Parsing Libraries Comparison in Java

Conclusion

From the above, we conclude that JSON is used to get or send data from web services or APIs. Java has many libraries that can help you to parse the JSON. Jackson is a powerful and widely used library that can convert JSON to Java objects and back. Gson is also popular and can be very easy to use. The org.json library is simple and can be helpful for small projects. JSON.simple can be a good choice if you are just starting. JSON-P might be useful when you are working with Java EE or web applications. 

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How to Parse JSON in Java – FAQs