flutter-handling-http-and-json

Handling HTTP and JSON

Contents

• Core Guidelines
• Workflow: Executing HTTP Operations
• Workflow: Implementing JSON Serialization
• Workflow: Parsing Large JSON in the Background
• Examples

Core Guidelines

• Enforce HTTPS: iOS and Android disable cleartext (HTTP) connections by default. Always use HTTPS endpoints. If HTTP is strictly required for debugging, configure network_security_config.xml (Android) and NSAppTransportSecurity (iOS).
• Construct URIs Safely: Always use Uri.https(authority, unencodedPath, [queryParameters]) to safely build URLs. This handles encoding and formatting reliably, preventing string concatenation errors.
• Handle Status Codes: Always validate the http.Response.statusCode. Treat 200 (OK) and 201 (Created) as success. Throw explicit exceptions for other codes (do not return null).
• Prevent UI Jank: Move expensive JSON parsing operations (taking >16ms) to a background isolate using the compute() function.
• Structured AI Output: When integrating LLMs, enforce reliable JSON output by specifying a strict JSON schema in the system prompt and setting the response MIME type to application/json.

Workflow: Executing HTTP Operations

Use this workflow to implement network requests using the http package.

Task Progress:

• Add the http package to pubspec.yaml.
• Configure platform permissions (Internet permission in AndroidManifest.xml and macOS .entitlements).
• Construct the target Uri.
• Execute the HTTP method.
• Validate the response and parse the JSON payload.

Conditional Implementation:

• If fetching data (GET): Use http.get(uri).
• If sending new data (POST): Use http.post(uri, headers: {...}, body: jsonEncode(data)). Ensure Content-Type is application/json; charset=UTF-8.
• If updating data (PUT): Use http.put(uri, headers: {...}, body: jsonEncode(data)).
• If deleting data (DELETE): Use http.delete(uri, headers: {...}).