One required step is to sign the Jar File with a trusted certificate (e.g. verisign or other) I think the current timestamp of the signed jarfile is out of date.
Then it should work.
But fpr your purpose you could use the Webutil libraries from Oracle.
When you play with JavaBeans, ALLWAYS display the Java console at runtime to see what happen (or not).
As Holger mentioned, rather than using a custom Java Bean you can use the Oracle provided WebUtil. Although this will be somewhat overkill for just one function (upload/download), WebUtil is provided with a pre-signed jar file and is mostly configured out of the box. Further, Oracle supports WebUtil. Oracle will not support your custom Java Bean if you have issues with it.
Also, it is important that you use Java 8. Java 7 is extremely old and is no longer supported. Finally, self-generated certificates should no longer be used. You can make them work, but this is not recommended and will eventually be removed from support in Java. You need a certificate provided from a trusted/known CA (e.g. Verisign, Thawte, etc)
You need to verify your jar file in the right way:
DOS> jarsigner -verify <file.jar>
Hope that helps,