ETag class

Middleware that automatically generates and validates ETags.

This middleware intercepts responses and:

Generates an ETag based on the response content
Compares with the client's If-None-Match header
Returns 304 Not Modified if they match
Otherwise, adds the ETag header to the response

Note: This middleware buffers the response body to compute the ETag. For large responses, consider using the ETag context extension methods in your handlers instead.

Features:

Automatic ETag generation using MD5 hash
Support for weak ETags
If-None-Match header validation
304 Not Modified responses for cached content
Custom ETag generator support

Example usage:

// Automatic ETag for all responses
app.use(ETag());

// Weak ETags
app.use(ETag(const ETagOptions.weak()));

// Custom generator
app.use(ETag(ETagOptions(
  generator: (content) => sha256.convert(content).toString(),
)));

// Manual ETag in handler
app.get('/data').handle((ctx) async {
  final data = await fetchData();
  final etag = '"${data.version}"';

  if (await ctx.checkEtag(etag)) {
    return; // 304 sent
  }

  await ctx.res.json(data);
});

HTTP Caching Flow:

First request: Server returns response with ETag header
Subsequent requests: Client sends If-None-Match with cached ETag
If ETag matches: Server returns 304 Not Modified (no body)
If ETag differs: Server returns new response with new ETag

Constructors

Properties

Methods

Operators

chase library