web-app8 min

Saving Data to a Database

Reading is only half the story. Let's handle form submissions so users can write data to your database. The pattern is always the same: read the body, validate, insert, respond.

A POST endpoint reads form fields from the request body:

    POST "/messages" :\n        string content = req.body("content")\n        string author = req.body("author")\n        if content == ""\n            return http.respond(400, "text/plain", "Content is required")\n        string params = "[\\"" + author + "\\", \\"" + content + "\\"]"\n        db.query("INSERT INTO messages (author, content) VALUES (?, ?)", params)\n        return http.respond(201, "text/plain", "Message saved!")

POST /messages (with form data)  → 201 Message saved!\nPOST /messages (empty content)   → 400 Content is required

req.body("field") reads a form field from the POST body. Validate before inserting — return 400 for bad input. Return 201 Created when a new resource is successfully created. The params order must match the ? placeholder order in your SQL.

A complete route pair: GET shows a form, POST handles it:

    GET "/messages/new" :\n        html:\n            <form method="post" action="/messages">\n                <input name="author" placeholder="Your name">\n                <textarea name="content" placeholder="Message"></textarea>\n                <button type="submit">Send</button>\n            </form>\n\n    POST "/messages" :\n        string content = req.body("content")\n        string author = req.body("author")\n        if content == ""\n            return http.respond(400, "text/plain", "Content is required")\n        string params = "[\\"" + author + "\\", \\"" + content + "\\"]"\n        db.query("INSERT INTO messages (author, content) VALUES (?, ?)", params)\n        return http.respond(200, "text/html", "<p>Saved! <a href='/messages/new'>Send another</a></p>")

GET  /messages/new → HTML form\nPOST /messages     → 200, confirmation message

GET shows the form, POST processes it. This GET-POST pair is the foundation of every web form. In production you'd redirect after POST to prevent double-submission, but this pattern is the right starting point.

Quick recap

POST endpoints use req.body("fieldname") to read submitted form fields
Validate input before writing to the database — return 400 for invalid data
201 Created is the conventional status for a successfully created resource
Build params as a JSON array — values must match ? placeholder order