Often, you'll deploy a on a web server, and it'll be accessible to phones through "over-the-air" (OTA) provisioning. To do this correctly requires the correct mime types for both .jad and .jar files. Below is a sample .htacess file for reference.
AddType text/vnd.sun.j2me.app-descriptor jad AddType application/java-archive jar addtype text/vnd.wap.wml wml addtype application/vnd.wap.wmlc wmlc addtype text/vnd.wap.wmlscript wmls addtype application/vnd.wap.wmlscriptc wmlsc addtype image/vnd.wap.wbmp wbmp
During development, you're going to want to take advantage of the plugin and toolkit's ability to generate your MIDlet-Jar-URL for you. However, the plugin generates a relative URL, which won't work as the specification for a .JAD is an absolute URL.
Simply add the properties you want to appear in the .JAD by adding elements to the jadAttributes section of the configuration section of the plugin, in the .pom.
<MIDlet-Jar-URL>http://codecafe.dev-hda.com/apps/jargoneer/codecafe-samples-2.0.1-SNAPSHOT-me.jar</MIDlet-Jar-URL>