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

4 次查看（过去 30 天）
buer
buer 2014-11-20
回答： buer 2014-12-17
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
显示 10更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

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

在 Help Center 和 File Exchange 中查找有关 Call Java from MATLAB 的更多信息

标签

Community Treasure Hunt

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

Start Hunting!

Translated by