Dart RedirectInfo
last modified April 4, 2025
The RedirectInfo class in Dart provides information about HTTP
redirects that occur during network requests. It's part of Dart's
dart:io library for server-side and command-line applications.
RedirectInfo contains details about redirect responses including status code, location, and method. It helps track and analyze redirect chains in HTTP communication.
Basic Definition
RedirectInfo is an immutable class representing a single HTTP
redirect. It's typically obtained from HttpClientResponse redirects.
Key properties include statusCode, method, and location. These help understand and process redirects in HTTP clients and servers.
Basic RedirectInfo Usage
This example shows how to access RedirectInfo from an HTTP client response.
import 'dart:io';
void main() async {
var client = HttpClient();
try {
var request = await client.getUrl(Uri.parse('http://example.org'));
var response = await request.close();
if (response.redirects.isNotEmpty) {
var redirect = response.redirects.first;
print('Redirected to: ${redirect.location}');
print('Status code: ${redirect.statusCode}');
print('Method: ${redirect.method}');
}
} finally {
client.close();
}
}
We create an HTTP client and check for redirects in the response. The first redirect's details are printed if any redirects occurred.
$ dart main.dart Redirected to: https://example.org/ Status code: 301 Method: GET
Analyzing Redirect Chains
This example demonstrates examining a complete redirect chain.
import 'dart:io';
void main() async {
var client = HttpClient();
try {
var request = await client.getUrl(Uri.parse('http://google.com'));
var response = await request.close();
print('Final URL: ${response.redirects.last.location}');
print('Redirect chain length: ${response.redirects.length}');
for (var redirect in response.redirects) {
print('${redirect.statusCode} ${redirect.method} -> ${redirect.location}');
}
} finally {
client.close();
}
}
We print each redirect in the chain with its status code and method. This helps understand complex redirect sequences.
$ dart main.dart Final URL: https://www.google.com/ Redirect chain length: 2 301 GET -> https://google.com/ 301 GET -> https://www.google.com/
Following Redirects Manually
This example shows manual redirect following using RedirectInfo.
import 'dart:io';
void main() async {
var client = HttpClient();
var url = Uri.parse('http://example.org');
var maxRedirects = 5;
var currentRedirect = 0;
try {
while (currentRedirect < maxRedirects) {
var request = await client.getUrl(url);
var response = await request.close();
if (response.redirects.isEmpty) {
print('Final destination: $url');
break;
}
var redirect = response.redirects.first;
print('Redirect $currentRedirect: ${redirect.location}');
url = Uri.parse(redirect.location.toString());
currentRedirect++;
}
} finally {
client.close();
}
}
We manually follow redirects up to a maximum limit. This demonstrates how to implement custom redirect logic when needed.
$ dart main.dart Redirect 0: https://example.org/ Final destination: https://example.org/
Handling Different Redirect Types
This example shows how to handle various redirect status codes.
import 'dart:io';
void main() async {
var client = HttpClient();
try {
var request = await client.getUrl(Uri.parse('http://test.com/temporary'));
var response = await request.close();
if (response.redirects.isNotEmpty) {
var redirect = response.redirects.first;
switch (redirect.statusCode) {
case HttpStatus.movedPermanently:
print('Permanent redirect to ${redirect.location}');
break;
case HttpStatus.found:
print('Temporary redirect to ${redirect.location}');
break;
case HttpStatus.seeOther:
print('See other (change method to GET) to ${redirect.location}');
break;
default:
print('Unknown redirect type: ${redirect.statusCode}');
}
}
} finally {
client.close();
}
}
We check the status code to determine the redirect type. Different HTTP status codes indicate different redirect semantics.
$ dart main.dart Temporary redirect to http://test.com/new-location
Creating Custom Redirect Policies
This example demonstrates implementing a custom redirect policy.
import 'dart:io';
class SecureRedirectPolicy {
bool allowRedirect(RedirectInfo redirect) {
if (redirect.location.scheme != 'https') {
print('Blocking insecure redirect to ${redirect.location}');
return false;
}
return true;
}
}
void main() async {
var client = HttpClient();
var policy = SecureRedirectPolicy();
try {
client.maxRedirects = 10;
client.autoUncompress = false;
var request = await client.getUrl(Uri.parse('http://bank.com/login'));
var response = await request.close();
for (var redirect in response.redirects) {
if (!policy.allowRedirect(redirect)) {
print('Aborting due to redirect policy violation');
return;
}
}
print('Successfully followed redirects to secure destination');
} finally {
client.close();
}
}
We implement a security policy that blocks redirects to non-HTTPS URLs. This shows how to use RedirectInfo for security validation.
$ dart main.dart Blocking insecure redirect to http://bank.com/login Aborting due to redirect policy violation
Best Practices
- Limit redirects: Set maxRedirects to prevent infinite loops
- Validate URLs: Check redirect locations for security
- Preserve method: Handle 307/308 status codes correctly
- Log redirects: Record redirect chains for debugging
- Handle errors: Prepare for malformed redirect locations
Source
Dart RedirectInfo Documentation
This tutorial covered Dart's RedirectInfo class with practical examples showing redirect handling, chain analysis, and custom security policies.
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