Try this:

NOTE: this file is in the folder labeled "example1"

====example1/MyGBean.java====
  1 package example1;
  2
  3 import org.apache.geronimo.gbean.GBeanInfo;
  4 import org.apache.geronimo.gbean.GBeanInfoBuilder ;
  5
  6 public class MyGBean {
  7
  8     public static final GBeanInfo GBEAN_INFO;
  9
 10     static {
 11         GBeanInfoBuilder infoBuilder = new GBeanInfoBuilder("MyGBean", MyGBean.class );
 12         GBEAN_INFO = infoBuilder.getBeanInfo();
 13     }
 14
 15     public static GBeanInfo getGBeanInfo() {
 16         return GBEAN_INFO;
 17     }
 18 }

====mygbean.xml====
  1 <?xml version=" 1.0" encoding="UTF-8"?>
  2 <module xmlns="http://geronimo.apache.org/xml/ns/deployment-1.2">
  3     <environment>
  4         <moduleId>
  5             <groupId>example1</groupId>
  6             <artifactId>MyGBean</artifactId>
  7             <version>1.0</version>
  8             <type>jar</type>
  9         </moduleId>
 10     </environment>
 11     <gbean name="MySimpleGBean" class="example1.MyGBean"/>
 12 </module>

1. Execute these commands
javac -classpath <geronimo_home>/lib/geronimo- kernel-2.0.1.jar example1/MyGBean.jar
jar -cvf mygbean.jar example1/*.class

2. Run the server

3. Execute this command from <geronimo_home>/bin dir
java -jar ./deployer.jar -u system -p manager deploy <mygbeanDir>/mygbean.jar <mygbeanDir>/mygbean.xml

I hope this works for you,
Viet