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Trail: Servlets

## Lesson: The Servlet Life Cycle

> Each servlet has the same life cycle:

> - A server loads and initializes the servlet
> - The servlet handles zero or more client requests
> - The server removes the servlet
>   (some servers do this step only when they shut down)

### Initializing a Servlet

> When a server loads a servlet, the server runs the servlet's `init` method. Initialization completes before client requests are handled and before the servlet is destroyed.

> Even though most servlets are run in multi-threaded servers, servlets have no concurrency issues during servlet initialization. The server calls the `init` method once, when the server loads the servlet, and will not call the init method again unless the server is reloading the servlet. The server can not reload a servlet until after the server has destroyed the servlet by running the `destroy` method.

### Interacting with Clients

> After initialization, the servlet is able to handle client requests. This part of the servlet life cycle was handled in the previous lesson.

### Destroying a Servlet

> Servlets run until the server destroys them, for example, at the request of a system administrator. When a server destroys a servlet, the server runs the servlet's `destroy` method. The method is run once; the server will not run the `destroy` method again until after the server reloads and reinitializes the servlet.

> When the server calls the `destroy` method, another thread might be running a service request. The Handling Service Threads at Servlet Termination lesson shows you how to provide a clean shutdown when there could be long-running threads still running service requests.

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