You can extend the vSphere Web Client by adding actions. You can add actions to existing vSphere objects, or create actions associated with a new type of vSphere object.
In the vSphere Web Client, actions represent commands that the user can issue to manage, administer, or otherwise manipulate the objects in the vSphere environment. Each action in the vSphere Web Client is associated with one or more specific vSphere object types. For example, the user might perform an action to change the power state of a selected Virtual Machine object, or to cause a Host object to enter or exit maintenance mode.
When you add an action extension to the vSphere Web Client user interface layer, you must also extend the vSphere Web Client service layer with a Java service. The Java service is responsible for performing the action operation on the target vSphere object.
You can extend the vSphere Web Client by adding actions associated with an existing type of vSphere object, or with a new type of vSphere object. You might add actions to an existing object type if you have created a custom version of that vSphere object, such as a custom host.
In addition to creating the action extension in the user interface layer, you must also add a Java service to the vSphere Web Client service layer. This Java service is used to perform the action operation on the target vSphere object.