Demystifying JSON Parsing in Salesforce: Apex and LWC Techniques


JSON (JavaScript Object Notation) is a widely used data interchange format, especially in web development. In Salesforce, JSON plays a significant role in integrating with external systems and handling data. In this blog, we will explore how to parse JSON in both Apex (Salesforce backend language) and LWC (Lightning Web Components, Salesforce frontend technology) using various techniques. We’ll provide examples, use cases, and guide you in selecting the correct option based on your specific requirements.


Understanding JSON and Its Structure

JSON is a lightweight data-interchange format that is easy for humans to read and write and straightforward for machines to parse and generate. It consists of key-value pairs, arrays, and nested objects, making it flexible and versatile. An example of a simple JSON object:

"name": "John Doe",
"age": 30,
"email": "",
"isEmployee": true
view raw example.json hosted with ❤ by GitHub

Parsing JSON in Apex

Apex provides several methods for parsing JSON:

  1. JSON.deserializeUntyped(): The JSON.deserializeUntyped() method is useful when you need to handle JSON data with unknown or dynamic structure. It parses the JSON data into a generic Object, which you can then traverse and access its properties. Example:
    String jsonString = '{"name":"John Doe","age":30,"email":"","isEmployee":true}';
    Object parsedObj = JSON.deserializeUntyped(jsonString);
    String name = (String)parsedObj.get('name');
    Integer age = (Integer)parsedObj.get('age');
    Boolean isEmployee = (Boolean)parsedObj.get('isEmployee');
    view raw ApexScript.cls hosted with ❤ by GitHub
  2. JSON.deserialize(): The JSON.deserialize() method is used when you have a known JSON structure, and you want to map it to a specific Apex class. This method is type-safe and allows for easier handling of JSON data. Example:
    public class Person {
    public String name;
    public Integer age;
    public String email;
    public Boolean isEmployee;
    String jsonString = '{"name":"John Doe","age":30,"email":"","isEmployee":true}';
    Person personObj = (Person)JSON.deserialize(jsonString, Person.class);
    view raw Example.cls hosted with ❤ by GitHub
  3. Using Custom Apex Classes: For more complex JSON structures, creating custom Apex classes to represent the JSON schema can be beneficial. This approach provides clear data modeling and easy access to properties.
    public class Address {
    public String street;
    public String city;
    public String zipCode;
    public class Customer {
    public String name;
    public Integer age;
    public Address address;
    String jsonString = '{"name":"John Doe","age":30,"address":{"street":"123 Main St","city":"New York","zipCode":"10001"}}';
    Customer customerObj = (Customer)JSON.deserialize(jsonString, Customer.class);
    view raw customApex.cls hosted with ❤ by GitHub

Parsing JSON in LWC (JavaScript)

In Lightning Web Components, you can use JavaScript methods for parsing JSON data:

  1. JSON.parse(): The JSON.parse() method is used to parse a JSON string and convert it into a JavaScript object. Example:
    const jsonString = '{"name":"John Doe","age":30,"email":"","isEmployee":true}';
    const parsedObj = JSON.parse(jsonString);
    const name =;
    const age = parsedObj.age;
    const isEmployee = parsedObj.isEmployee;
    view raw example.js hosted with ❤ by GitHub
  2. LWC @wire Service: When retrieving JSON data from Apex controllers in LWC, you can use the @wire service to automatically parse the JSON response into the appropriate data format. Example:
    import { LightningElement, wire } from 'lwc';
    import getCustomerData from '@salesforce/apex/MyController.getCustomerData';
    export default class MyComponent extends LightningElement {
    wiredCustomerData({ error, data }) {
    if (data) {
    this.customerData = data;
    } else if (error) {
    console.error('Error fetching customer data: ', error);
    view raw MyComponent.js hosted with ❤ by GitHub
  3. Fetch API with JSON: When making API calls from LWC to external services that return JSON data, you can use the Fetch API to parse the JSON response. Example:
    .then((response) => response.json())
    .then((data) => {
    // Use the parsed JSON data
    .catch((error) => {
    console.error('Error fetching data: ', error);
    view raw fetchAPI.js hosted with ❤ by GitHub

Use Cases for Different JSON Parsing Techniques

  • Use JSON.deserializeUntyped() in Apex when dealing with unknown JSON structures or when you need to handle dynamic data.
  • Use JSON.deserialize() in Apex when you have a known JSON structure and want to map it to a specific Apex class.
  • Use custom Apex classes in Apex when working with complex JSON structures and to create a clear data model for the JSON schema.
  • Use <strong>JSON.parse()</strong> in LWC (JavaScript) when you need to parse JSON strings into JavaScript objects.
  • Use the LWC @wire service to automatically parse JSON responses from Apex controllers in Lightning Web Components.
  • Use the Fetch API with JSON to handle JSON responses from external APIs in LWC.


In this blog, we explored various techniques for parsing JSON in both Apex and LWC (JavaScript) with examples. Understanding JSON parsing methods is crucial for integrating with external systems, handling data, and building efficient Salesforce applications. Whether you choose to use Apex’s JSON.deserialize() or LWC’s JSON.parse(), the appropriate method depends on the complexity of the JSON data and the use case at hand. By utilizing the correct JSON parsing approach, you can efficiently work with JSON data and build robust Salesforce applications.

About the blog

SFDCLessons is a blog where you can find various Salesforce tutorials and tips that we have written to help beginners and experienced developers alike. we also share my experience and knowledge on Salesforce best practices, troubleshooting, and optimization. Don’t forget to follow us on:


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Arun Kumar

Arun Kumar is a Salesforce Certified Platform Developer I with over 7+ years of experience working on the Salesforce platform. He specializes in developing custom applications, integrations, and reports to help customers streamline their business processes. Arun is passionate about helping businesses leverage the power of Salesforce to achieve their goals.

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