read gmail inbox using javamail, works in eclipse but not outside - eclipse

Question

My code connects to a gmail account and reads each email received. I retrieve the content of the email message. I use javamail api for that.
When I run the code from eclipse, it works absolutely fine. But if I export everything into a jar file and then run from command prompt, then I get the following error :
java.lang.ClassCastException: com.sun.mail.imap.IMAPInputStream cannot be cast to javax.mail.Multipart
in the following line :
Multipart mp = (Multipart) msg.getContent();
I tried using this but it doesn't help :
public static void main(String[] args) throws Exception {
System.out.println("Begin");
Thread.currentThread().setContextClassLoader(getOldIds.class.getClassLoader());
//read emails
}
Properties props = System.getProperties();
props.setProperty("mail.store.protocol", "imaps");
Session session = Session.getInstance(props, null);
Store store = session.getStore("imaps");
store.connect("imap.gmail.com", -1, "username", "password");
//fetch the message from the inbox
Please suggest me what should be done.
Thanks

Answer 1

Add this line to your code :-
MimeMessage mimemsg = new MimeMessage(msg);
Multipart mp = (Multipart) mimemsg.getContent();
instead of :-
Multipart mp = (Multipart) msg.getContent();
Here I am safely assuming that msg if of type com.sun.mail.imap.IMAPMessage

Answer 2

How are you exporting everything into a jar file?
If you're combining all your application classes and all the JavaMail classes from the mail.jar file into a single new jar file, you're missing the resource files from the mail.jar file that configure the mapping from MIME type to Java class.
Your application classes should be in one jar file and that jar file should reference or use the JavaMail jar file, e.g., on the CLASSPATH when the application runs.

Answer 3

Thanks everyone for help...... the approach below worked for me :
BufferedReader br = new BufferedReader( new InputStreamReader(msg.getInputStream()));
content="";
String line;
while((line=br.readLine())!=null){
content = content + line;
}
System.out.println("\n\n" + content);
br.close();