How do I provide a username/password to access a web resource using Matlab urlread/urlwrite?

Question

Following on from this question, regarding accessing a PDF on a web page using Matlab which is originally buried behind a Javascript function. I now have a URL which allows me to access the page directly, this works okay using the Matlab webrowser object (the PDF appears on screen), but to save the PDF for subsequent processing I appear to need to use the Matlab urlread/urlwrite functions. However, these functions provide no method for offering authentication credentials.

How do I provide username/password for Matlab's urlread/urlwrite functions?

Answer 1

Matlab's urlread() function has a "params" argument, but these are CGI-style parameters that get encoded in the URL. Authentication is done with lower-level HTTP Request parameters. Urlread doesn't support these, but you can code directly against the Java URL class to use them.

You can also use a Sun's sun.misc.BASE64Encoder class to do the Base 64 encoding programmatically. This is a nonstandard class, not part of the standard Java library, but you know that the JVM shipping with Matlab will have it, so you can get away with coding to it.

Here's a quick hack showing it in action.

function [s,info] = urlread_auth(url, user, password)
%URLREAD_AUTH Like URLREAD, with basic authentication
%
% [s,info] = urlread_auth(url, user, password)
%
% Returns bytes. Convert to char if you're retrieving text.
%
% Examples:
% sampleUrl = 'http://browserspy.dk/password-ok.php';
% [s,info] = urlread_auth(sampleUrl, 'test', 'test');
% txt = char(s)

% Matlab's urlread() doesn't do HTTP Request params, so work directly with Java
jUrl = java.net.URL(url);
conn = jUrl.openConnection();
conn.setRequestProperty('Authorization', ['Basic ' base64encode([user ':' password])]);
conn.connect();
info.status = conn.getResponseCode();
info.errMsg = char(readstream(conn.getErrorStream()));
s = readstream(conn.getInputStream());

function out = base64encode(str)
% Uses Sun-specific class, but we know that is the JVM Matlab ships with
encoder = sun.misc.BASE64Encoder();
out = char(encoder.encode(java.lang.String(str).getBytes()));

%%
function out = readstream(inStream)
%READSTREAM Read all bytes from stream to uint8
try
    import com.mathworks.mlwidgets.io.InterruptibleStreamCopier;
    byteStream = java.io.ByteArrayOutputStream();
    isc = InterruptibleStreamCopier.getInterruptibleStreamCopier();
    isc.copyStream(inStream, byteStream);
    inStream.close();
    byteStream.close();
    out = typecast(byteStream.toByteArray', 'uint8'); %'
catch err
    out = []; %HACK: quash
end