无法通过Java Servlet发送电子邮件

Question

I am getting this error when trying to send emails via gmail smtp inside servlet it works locally when tested but not inside google engine i added the libs under web-inf/libs [activation.jar-smtp.jar- mailapi.jar - mail.jar] any idea how i can fix it!!

Error: javax.servlet.ServletContext log: unavailable java.lang.SecurityException: SHA1 digest error for javax/mail/Message.class at com.google.appengine.run

Code Snapshot:

 Properties props = new Properties();
 props.setProperty("mail.transport.protocol", "smtp");
 props.setProperty("mail.host", "smtp.gmail.com");
 props.put("mail.smtp.auth", "true"); 
 props.put("mail.smtp.port", "465"); 
 //props.put("mail.debug", "true");
 props.put("mail.smtp.socketFactory.port", "465");
 props.put("mail.smtp.socketFactory.class","javax.net.ssl.SSLSocketFactory");
 props.put("mail.smtp.socketFactory.fallback", "false");
 javax.mail.Session sess = javax.mail.Session.getInstance(props);
 Transport transport = sess.getTransport(); 
 transport.connect();
 transport.send(message);

Answer 1

You cannot use signed jar files on Google app engine.

As indicated on the web page, you should try to unsign it, specifically the mail.jar because the error is indicating javax/mail/Message.class , see this question for an example

Answer 2

App Engine's precompilation isn't compatible with signed JAR files. If your application is precompiled (the default), it can't load signed JAR files. If the application tries to load a signed JAR, at runtime App Engine will generate an exception like yours.
No Signed JAR Files

There is two way to work around.

1. Strip the JAR's signature
2. Disabling Precompilation