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Send and Receive HTTP Messages

This example shows how to send a request to a server that involves redirection and might require digest authentication.

The sendRequest function automatically redirects and authenticates on the first request. For subsequent requests, you do not want to pay the cost of a redirect. To do this, sendRequest saves the cookies received on previous requests and reuses them for subsequent requests.

sendRequest illustrates the use of the history, the reuse of a custom HTTPOptions object to change the default timeout, and the use of saved credentials.

This example does not illustrate a robust, general-purpose mechanism for achieving these results. In particular, sendRequest returns all cookies received from a host in every subsequent message to that host, regardless of the domain, path, expiration, or other properties. sendRequest also does not save credentials or cookies across MATLAB® sessions. Nonetheless, sendRequest is adequate for many applications.

Create the sendRequest function from the following code.

function response = sendRequest(uri,request)

% uri: matlab.net.URI
% request: matlab.net.http.RequestMessage
% response: matlab.net.http.ResponseMessage

% matlab.net.http.HTTPOptions persists across requests to reuse  previous
% Credentials in it for subsequent authentications
persistent options 

% infos is a containers.Map object where: 
%    key is uri.Host; 
%    value is "info" struct containing:
%        cookies: vector of matlab.net.http.Cookie or empty
%        uri: target matlab.net.URI if redirect, or empty
persistent infos

if isempty(options)
    options = matlab.net.http.HTTPOptions('ConnectTimeout',20);
end

if isempty(infos)
    infos = containers.Map;
end
host = string(uri.Host); % get Host from URI
try
    % get info struct for host in map
    info = infos(host);
    if ~isempty(info.uri)
        % If it has a uri field, it means a redirect previously
        % took place, so replace requested URI with redirect URI.
        uri = info.uri;
    end
    if ~isempty(info.cookies)
        % If it has cookies, it means we previously received cookies from this host.
        % Add Cookie header field containing all of them.
        request = request.addFields(matlab.net.http.field.CookieField(info.cookies));
    end
catch
    % no previous redirect or cookies for this host
    info = [];
end

% Send request and get response and history of transaction.
[response, ~, history] = request.send(uri, options);
if response.StatusCode ~= matlab.net.http.StatusCode.OK
    return
end

% Get the Set-Cookie header fields from response message in
% each history record and save them in the map.
arrayfun(@addCookies, history)

% If the last URI in the history is different from the URI sent in the original 
% request, then this was a redirect. Save the new target URI in the host info struct.
targetURI = history(end).URI;
if ~isequal(targetURI, uri)
    if isempty(info)
        % no previous info for this host in map, create new one
        infos(char(host)) = struct('cookies',[],'uri',targetURI);
    else
        % change URI in info for this host and put it back in map
        info.uri = targetURI;
        infos(char(host)) = info;
    end
end

    function addCookies(record)
        % Add cookies in Response message in history record
        % to the map entry for the host to which the request was directed.
        %
        ahost = record.URI.Host; % the host the request was sent to
        cookieFields = record.Response.getFields('Set-Cookie');
        if isempty(cookieFields)
            return
        end
        cookieData = cookieFields.convert(); % get array of Set-Cookie structs
        cookies = [cookieData.Cookie]; % get array of Cookies from all structs
        try
            % If info for this host was already in the map, add its cookies to it.
            ainfo = infos(ahost);
            ainfo.cookies = [ainfo.cookies cookies];
            infos(char(ahost)) = ainfo;
        catch
            % Not yet in map, so add new info struct.
            infos(char(ahost)) = struct('cookies',cookies,'uri',[]);
        end
    end
end

Call the function.

request = matlab.net.http.RequestMessage;
uri = matlab.net.URI('https://www.mathworks.com/products');
response = sendRequest(uri,request)
response =   ResponseMessage with properties:

    StatusLine: 'HTTP/1.1 200 OK'
    StatusCode: OK
        Header: [1×11 matlab.net.http.HeaderField]
          Body: [1×1 matlab.net.http.MessageBody]
     Completed: 0

Your response values might be different.

See Also

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