MATLAB: Webread certificate problems – roll your own java works, webread doesn’t. Why

MATLABwebread

Could someone explain to me why this would fail with an obscure message
webread('http://website/', 'Authorization', ['Basic ' matlab.net.base64encode(['me:secr3t'])]) 
The reason is "error:14090086:SSL routines:ssl3_get_server_certificate:certificate
verify failed". Check your certificate file (C:\Program Files\MATLAB\R2018a\sys\certificates\ca\rootcerts.pem) for expired, missing or invalid certificates.
Whereas this (lightly modified and shamelessly stolen from stack overflow) appears to have no problems. Is webread doing something kooky that causes it to barf on the proxy server, where java is not? Why does matlab have certificate problems?
urlread_auth('https://website/','me','secr3t' )
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 ' matlab.net.base64encode([user ':' password])]);
conn.connect();
info.status = conn.getResponseCode();
info.errMsg = char(readstream(conn.getErrorStream()));
s = readstream(conn.getInputStream());
end
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
end

Best Answer

See Jörgens comment above. https://ch.mathworks.com/matlabcentral/answers/376318-webread-certificate-problems-roll-your-own-java-works-webread-doesn-t-why#comment_528714
""" I solved it by setting the options=weboptions; options.CertificateFilename=(''); webread(URL,options); """
I also then needed to set the RequestMethod as POST, and crucially, use the 'webwrite' function, as opposed to the 'webread' function. Suddenly, things burst into life ...
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