HttpResponse class Null safety

An HTTP response, which returns the headers and data from the server to the client in response to an HTTP request.

Every HttpRequest object provides access to the associated HttpResponse object through the response property. The server sends its response to the client by writing to the HttpResponse object.

Writing the response

This class implements IOSink. After the header has been set up, the methods from IOSink, such as writeln(), can be used to write the body of the HTTP response. Use the close() method to close the response and send it to the client.

server.listen((HttpRequest request) {
  request.response.write('Hello, world!');
  request.response.close();
});

When one of the IOSink methods is used for the first time, the request header is sent. Calling any methods that change the header after it is sent throws an exception.

Setting the headers

The HttpResponse object has a number of properties for setting up the HTTP headers of the response. When writing string data through the IOSink, the encoding used is determined from the "charset" parameter of the "Content-Type" header.

HttpResponse response = ...
response.headers.contentType
    = new ContentType("application", "json", charset: "utf-8");
response.write(...);  // Strings written will be UTF-8 encoded.

If no charset is provided the default of ISO-8859-1 (Latin 1) will be used.

HttpResponse response = ...
response.headers.add(HttpHeaders.contentTypeHeader, "text/plain");
response.write(...);  // Strings written will be ISO-8859-1 encoded.

An exception is thrown if you use the write() method while an unsupported content-type is set.