Start by creating an empty directory in some suitable location on your hard disk. Inside this directory, create two more directories META-INF and resources.

Copy the XML code below and save it to META-INF/extensions.xml in your newly created directory. It is important that you get the filename correct.

<?xml version="1.0" encoding="UTF-8" ?>
<extensions xmlns="http://base.thep.lu.se/extensions.xsd">
   <extension
      id="net.sf.basedb.clients.web.menu.extensions.helloworld"
      extends="net.sf.basedb.clients.web.menu.extensions"
      >
      <index>1</index>
      <about safe-scripts="1">
         <name>Hello world</name>
         <description>
            The very first extensions example. Adds a "Hello world"
            menu item that displays "Hello world" in a javascript
            popup when selected.
         </description>
      </about>
      <action-factory>
         <factory-class>	
            net.sf.basedb.clients.web.extensions.menu.FixedMenuItemFactory
         </factory-class>
         <parameters>
         	<id>hello-world</id>
            <title>Hello world!</title>
            <tooltip>This is to test the extensions system</tooltip>
            <icon>/images/info.png</icon>
            <script>~/hello.js</script>
         </parameters>
      </action-factory>
   </extension>
</extensions>

This file is the most important one when creating extensions since it is used to tell BASE about the extensions (and plug-ins) in the package. See below for more information.

Copy the javascript code below and save it to resources/hello.js in your newly created directory. Once again, it is important that the filename is correct.

var HelloWorld = function()  
{  
   var hello = {};  
    
    /** 
       Executed once when the page is loaded. Typically 
       used to bind events to fixed control elements. 
    */  
    hello.initMenuItems = function()  
    {  
       // Bind event handlers the menu items.   
       // First parameter is the ID of the menu item  
       // Second parameter is the event to react to (=click)  
       // Last parameter is the function to execute  
       Events.addEventHandler('hello-world', 'click', hello.helloWorld);  
    }  
      
    // Show 'Hello world' message
    hello.helloWorld = function(event)  
    {  
       alert('Hello world');
    }  
     
    return hello;  
}();  
      
//Register the page initializer method with the BASE core  
Doc.onLoad(HelloWorld.initMenuItems);  

Create a JAR package containing the two directories and files you have created. It is important the the subdirectory structure inside the JAR file is rooted at the first empty directory you created.

Copy the JAR file to the the plugins.dir directory for your BASE installation.

Log in to BASE and install the extension by going through the installation wizard at AdministratePlug-ins & extensionsOverview. When the extension has been installed you should have a new menu item: ExtensionsHello world! which pops up a message in a Javascript window.

	Note
	You may have to logout and login again to see the new menu item.