How Does the Post/Redirect/Get (PRG) Pattern Prevent Duplicate Form Submissions?

Approaching the "Post/Redirect/Get" Pattern

While the "post/redirect/get" pattern has been explained as a concept, its intricacies can be perplexing. Allow us to unravel this process step by step for a better understanding.

The Problem:

When submitting a form, consider a scenario where you want to prevent resubmissions after a page refresh. If a simple POST request is used, refreshing the page would re-submit the form, potentially leading to unwanted duplicate entries.

The Solution: "Post/Redirect/Get" Pattern

This pattern consists of three distinct stages:

1. Post: A form is submitted using a POST request, sending data to the server.
2. Redirect: Upon successful submission, the server responds with a redirect (usually a 302 status code) to a new URL.
3. Get: The browser follows the redirect and makes a GET request to the new URL, displaying the appropriate page.

Advantages of PRG:

• Prevents duplicate form submissions: Since the form is not submitted again, there is no risk of duplicate entries upon page refresh.
• Preserves browser history: The GET request in the third step lets browsers maintain a proper history of page visits.
• Improves security: By keeping sensitive data (such as passwords) out of the URL, PRG enhances security.

Understanding the Diagram:

The provided diagram illustrates the flow of the PRG pattern.

• The "bad" example shows that refreshing the form after a POST request would result in a resubmission, while the "good" example shows proper handling using a redirect and GET request.

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