Matlab using Java openStream(url) get :Java exception occurred: java.lang.​NullPointe​rException

5 次查看(过去 30 天)
Hi,
I want to download one file from a URL. According to this: http://www.mathworks.com/matlabcentral/newsreader/view_thread/294528. all works fine until i go to the line: is = jurl.openStream; This gave one error says Java exception occurred: java.lang.NullPointerException.
Anyone can help? thanks
  12 个评论

请先登录,再进行评论。

采纳的回答

buer
buer 2014-12-17
Yes. so the answer is Matlab urlread does not support authentication with lower level request. So we need to code firectly against the Java URL class to use them:
% 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
Hope it will help others later.

更多回答(0 个)

类别

Help CenterFile Exchange 中查找有关 Call Java from MATLAB 的更多信息

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by