Consuming rest services (CRUD operations) using Jquery AJAX and JSON

Consuming REST Services (CRUD operations) using jQuery AJAX and JSON

When consuming RESTful services from a web client, jQuery and AJAX (Asynchronous JavaScript and XML) are commonly used to make HTTP requests and interact with RESTful APIs. The most common format for transferring data between the client and the server in REST APIs is JSON (JavaScript Object Notation).

In this guide, we'll cover how to perform CRUD (Create, Read, Update, Delete) operations using jQuery AJAX and JSON for consuming RESTful services.

Overview of CRUD Operations:

• Create (POST): Sends data to the server to create a new resource.
• Read (GET): Retrieves data from the server (e.g., a list of resources or a single resource).
• Update (PUT or PATCH): Sends updated data to the server to modify an existing resource.
• Delete (DELETE): Sends a request to remove a resource from the server.

---

Step-by-Step Guide to CRUD Operations with jQuery AJAX

Assuming the API you're consuming has endpoints like the following:

• GET /api/books: Get a list of all books.
• GET /api/books/{id}: Get a specific book by its id.
• POST /api/books: Add a new book.
• PUT /api/books/{id}: Update an existing book.
• DELETE /api/books/{id}: Delete a book.

Let’s look at how to consume these operations using jQuery AJAX and JSON.

---

1. Create (POST): Adding a New Book

To add a new book, you would send a POST request with the book data (in JSON format) to the RESTful service.

Example jQuery AJAX for Creating a Book:

$(document).ready(function () {
    $('#addBookBtn').click(function () {
        var bookData = {
            title: $('#title').val(),
            author: $('#author').val(),
            year: $('#year').val()
        };

        $.ajax({
            url: 'http://localhost:8080/api/books',
            type: 'POST',
            contentType: 'application/json',
            data: JSON.stringify(bookData),
            success: function (response) {
                alert('Book added successfully!');
                // Optionally reload the list of books after adding
                loadBooks();
            },
            error: function (xhr, status, error) {
                alert('Error: ' + error);
            }
        });
    });
});

• Explanation:
  • The bookData object contains the details of the book that you want to add.
  • The $.ajax() method sends a POST request to the API endpoint.
  • The contentType is set to application/json because we're sending JSON data.
  • The data is the JSON stringified version of bookData.
  • On success, we alert the user and reload the list of books by calling loadBooks(), which you will implement in the "Read" operation.

---

2. Read (GET): Retrieving All Books

To get all books, you would send a GET request to the /api/books endpoint.

Example jQuery AJAX for Retrieving Books:

function loadBooks() {
    $.ajax({
        url: 'http://localhost:8080/api/books',
        type: 'GET',
        dataType: 'json',
        success: function (response) {
            var booksList = $('#booksList');
            booksList.empty(); // Clear the current list of books
            response.forEach(function (book) {
                booksList.append('<li>' + book.title + ' by ' + book.author + '</li>');
            });
        },
        error: function (xhr, status, error) {
            alert('Error: ' + error);
        }
    });
}

$(document).ready(function () {
    loadBooks(); // Load books on page load
});

• Explanation:
  • The loadBooks() function sends a GET request to the /api/books endpoint.
  • The server's response is expected to be in JSON format (dataType: 'json').
  • We loop through the list of books (response) and display them in an unordered list (#booksList).

---

3. Update (PUT): Updating an Existing Book

To update an existing book, you would send a PUT request with the updated book data to the /api/books/{id} endpoint.

Example jQuery AJAX for Updating a Book:

$(document).ready(function () {
    $('#updateBookBtn').click(function () {
        var bookId = $('#bookId').val(); // ID of the book to update
        var bookData = {
            title: $('#title').val(),
            author: $('#author').val(),
            year: $('#year').val()
        };

        $.ajax({
            url: 'http://localhost:8080/api/books/' + bookId,
            type: 'PUT',
            contentType: 'application/json',
            data: JSON.stringify(bookData),
            success: function (response) {
                alert('Book updated successfully!');
                loadBooks(); // Reload the list of books
            },
            error: function (xhr, status, error) {
                alert('Error: ' + error);
            }
        });
    });
});

• Explanation:
  • The bookId is the ID of the book to be updated, taken from the input field #bookId.
  • The bookData object contains the updated data for the book.
  • The PUT request sends the updated bookData as JSON to the /api/books/{id} endpoint.
  • After a successful update, we reload the list of books.

---

4. Delete (DELETE): Deleting a Book

To delete a book, you would send a DELETE request to the /api/books/{id} endpoint, where id is the ID of the book to be deleted.

Example jQuery AJAX for Deleting a Book:

$(document).ready(function () {
    $('#deleteBookBtn').click(function () {
        var bookId = $('#bookId').val(); // ID of the book to delete

        $.ajax({
            url: 'http://localhost:8080/api/books/' + bookId,
            type: 'DELETE',
            success: function (response) {
                alert('Book deleted successfully!');
                loadBooks(); // Reload the list of books
            },
            error: function (xhr, status, error) {
                alert('Error: ' + error);
            }
        });
    });
});

• Explanation:
  • The bookId is the ID of the book to be deleted, taken from the input field #bookId.
  • The DELETE request sends a request to the /api/books/{id} endpoint.
  • On success, the book is removed, and we reload the list of books.

---

Summary:

• Create (POST): Use AJAX to send JSON data to the server to create a new resource.
• Read (GET): Use AJAX to retrieve data from the server and display it on the page.
• Update (PUT): Use AJAX to send updated data to the server to modify an existing resource.
• Delete (DELETE): Use AJAX to delete a resource from the server.

Example HTML (to interact with the AJAX operations):

<!DOCTYPE html>
<html>
<head>
    <title>Books CRUD Operations</title>
    <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
    <script src="script.js"></script> <!-- Include your script file -->
</head>
<body>

<h1>Books CRUD Operations</h1>

<!-- Create Book Form -->
<input type="text" id="title" placeholder="Book Title">
<input type="text" id="author" placeholder="Author">
<input type="number" id="year" placeholder="Year">
<button id="addBookBtn">Add Book</button>

<br><br>

<!-- Update Book Form -->
<input type="number" id="bookId" placeholder="Book ID to update">
<button id="updateBookBtn">Update Book</button>

<br><br>

<!-- Delete Book Form -->
<input type="number" id="bookId" placeholder="Book ID to delete">
<button id="deleteBookBtn">Delete Book</button>

<h2>Books List</h2>
<ul id="booksList"></ul>

</body>
</html>

With this setup, your HTML form allows you to create, read, update, and delete books using the corresponding AJAX operations. Each operation interacts with the REST API using JSON and jQuery.