Understanding POST vs PUT in Web Development

When we use web services, sometimes it may trigger error when we are not careful to tell the difference between POST and PUT.

In the world of web development, especially when dealing with RESTful APIs, the HTTP methods POST and PUT are frequently used but often misunderstood. Both are used to send data to the server, but they serve different purposes and follow different rules.

POST: Creating New Resources

Definition

• POST is used to create a new resource on the server.

Idempotency

• POST requests are non-idempotent, meaning multiple identical POST requests will generally produce different results.

Usage Example

• Imagine you’re developing a blog platform. When a user writes a new blog post, you would use a POST request to send this new post data to the server. Each time a POST request is made, a new blog post is created.
• Example Request: POST /api/blogPosts with the new post data in the request body.

PUT: Updating Existing Resources

Definition

• PUT is used to update an existing resource or create a new one if it doesn’t exist, based on the provided identifier.

Idempotency

• PUT requests are idempotent. This means if you make the same PUT request multiple times, the result will be the same as making it once.

Usage Example

• Continuing with the blog platform scenario, if a user wants to edit an existing blog post, a PUT request is made. This request will carry the updated data and the unique identifier of the post (like its ID).
• Example Request: PUT /api/blogPosts/123 with the updated post data in the request body, where 123 is the post ID.

Key Differences

• Primary Function: POST creates, PUT updates (or creates if absent).
• Idempotency: POST is non-idempotent, PUT is idempotent.
• URL Usage: In POST, the URL typically points to a collection (e.g., /api/blogPosts), while PUT points to a specific item in the collection (e.g., /api/blogPosts/123).

Conclusion

Understanding the differences between POST and PUT is crucial for building effective and standards-compliant web applications. By using each method appropriately, developers can ensure that their APIs are intuitive and predictable, leading to better data integrity and easier maintenance.