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> ## The Example Servlets

> This chapter uses the Duke's Bookstore application to illustrate the tasks involved in programming servlets. Table 11-1 lists the servlets that handle each bookstore function. Each programming task is illustrated by one or more servlets. For example, `BookDetailsServlet` illustrates how to handle HTTP `GET` requests, `BookDetailsServlet` and `CatalogServlet` show how to construct responses, and `CatalogServlet` illustrates how to track session information.

> Table 11-1 Duke's Bookstore Example Servlets
> Function | Servlet
> --- | ---
> Enter the bookstore | `BookStoreServlet`
> Create the bookstore banner | `BannerServlet`
> Browse the bookstore catalog | `CatalogServlet`
> Put a book in a shopping cart | `CatalogServlet`, `BookDetailsServlet`
> Get detailed information on a specific book | `BookDetailsServlet`
> Display the shopping cart | `ShowCartServlet`
> Remove one or more books from the shopping cart | `ShowCartServlet`
> Buy the books in the shopping cart | `CashierServlet`
> Send an acknowledgment of the purchase | `ReceiptServlet`

> The data for the bookstore application is maintained in a database and accessed through the database access class `database.BookDBAO`. The `database` package also contains the class `BookDetails`, which represents a book. The shopping cart and shopping cart items are represented by the classes `cart.ShoppingCart` and `cart.ShoppingCartItem`, respectively.

> The source code for the bookstore application is located in the `<``INSTALL``>/j2eetutorial14/examples/web/bookstore1/` directory, which is created when you unzip the tutorial bundle (see Building the Examples). A sample `bookstore1.war` is provided in `<``INSTALL``>/j2eetutorial14/examples/web/provided-wars/`. To build the application, follow these steps:

> 1. Build and package the bookstore common files as described in Duke's Bookstore Examples.
> 2. In a terminal window, go to`<``INSTALL``>/j2eetutorial14/examples/web/bookstore1/`.
> 3. Run `asant` `build`. This target will spawn any necessary compilations and copy files to the `<``INSTALL``>/j2eetutorial14/examples/web/bookstore1/build/` directory.
> 4. Start the Application Server.
> 5. Perform all the operations described in Accessing Databases from Web Applications.

> To package and deploy the example using `asant`, follow these steps:

> 1. Run `asant` `create-bookstore-war`.
> 2. Run `asant` `deploy-war`.

> To learn how to configure the example, use `deploytool` to package and deploy it:

> 1. Start `deploytool`.
> 2. Create a Web application called `bookstore1` by running the New Web Component wizard. Select FileNewWeb Component.
> 3. In the New Web Component wizard:
> 1. Select the Create New Stand-Alone WAR Module radio button.
> 2. In the WAR Location field, enter `<``INSTALL``>/j2eetutorial14/examples/web/bookstore1/bookstore1.war`.
> 3. In the WAR Name field, enter `bookstore1`.
> 4. In the Context Root field, enter `/bookstore1`.
> 5. Click Edit Contents.
> 6. In the Edit Archive Contents dialog box, navigate to`<``INSTALL``>/j2eetutorial14/examples/web/bookstore1/build/`. Select `errorpage.html`, `duke.books.gif`, and the `servlets`, `database`, `filters`, `listeners`, and `util` packages. Click Add.
> 7. Add the shared bookstore library. Navigate to`<``INSTALL``>/j2eetutorial14/examples/web/bookstore/dist/`. Select `bookstore.jar` and click Add.
> 8. Click OK.
> 9. Click Next.
> 10. Select the Servlet radio button.
> 11. Click Next.
> 12. Select `BannerServlet` from the Servlet Class combo box.
> 13. Click Finish.
> 4. Add the rest of the Web components listed in Table 11-2. For each servlet:
> 1. Select FileNewWeb Component.
> 2. Click the Add to Existing WAR Module radio button. Because the WAR contains all the servlet classes, you do not have to add any more content.
> 3. Click Next.
> 4. Select the Servlet radio button.
> 5. Click Next.
> 6. Select the servlet from the Servlet Class combo box.
> 7. Click Finish.

>    Table 11-2 Duke's Bookstore Web Components
>    Web Component Name | Servlet Class | Alias
>    --- | --- | ---
>    BannerServlet | BannerServlet | `/banner`
>    `BookStoreServlet` | `BookStoreServlet` | `/bookstore`
>    `CatalogServlet` | `CatalogServlet` | `/bookcatalog`
>    `BookDetailsServlet` | `BookDetailsServlet` | `/bookdetails`
>    `ShowCartServlet` | `ShowCartServlet` | `/bookshowcart`
>    `CashierServlet` | `CashierServlet` | `/bookcashier`
>    `ReceiptServlet` | `ReceiptServlet` | `/bookreceipt`

> 5. Set the alias for each Web component.
> 1. Select the component.
> 2. Select the Aliases tab.
> 3. Click the Add button.
> 4. Enter the alias.
> 6. Add the listener class `listeners.ContextListener` (described in Handling Servlet Life-Cycle Events).
> 1. Select the Event Listeners tab.
> 2. Click Add.
> 3. Select the `listeners.ContextListener` class from the drop-down field in the Event Listener Classes pane.
> 7. Add an error page (described in Handling Errors).
> 1. Select the File Ref's tab.
> 2. In the Error Mapping pane, click Add Error.
> 3. Enter `exception.BookNotFoundException` in the Error/Exception field.
> 4. Enter `/errorpage.html` in the Resource to be Called field.
> 5. Repeat for `exception.BooksNotFoundException` and `javax.servlet.UnavailableException`.
> 8. Add the filters `filters.HitCounterFilter` and `filters.OrderFilter` (described in Filtering Requests and Responses).
> 1. Select the Filter Mapping tab.
> 2. Click Edit Filter List.
> 3. Click Add Filter.
> 4. Select `filters.HitCounterFilter` from the Filter Class column. `deploytool` will automatically enter `HitCounterFilter` in the Filter Name column.
> 5. Click Add Filter.
> 6. Select `filters.OrderFilter` from the Filter Class column. `deploytool` will automatically enter `OrderFilter` in the Filter Name column.
> 7. Click OK.
> 8. Click Add.
> 9. Select `HitCounterFilter` from the Filter Name drop-down menu.
> 10. Select the Filter this Servlet radio button in the Filter Target frame.
> 11. Select `BookStoreServlet` from the Servlet Name drop-down menu.
> 12. Click OK.
> 13. Repeat for `OrderFilter`. Select `ReceiptServlet` from the Servlet Name drop-down menu.
> 9. Add a resource reference for the database.
> 1. Select the Resource Ref's tab.
> 2. Click Add.
> 3. Enter `jdbc/BookDB` in the Coded Name field.
> 4. Accept the default type `javax.sql.DataSource`.
> 5. Accept the default authorization `Container`.
> 6. Accept the default selected `Shareable`.
> 7. Enter `jdbc/BookDB` in the JNDI name field of the Sun-specific Settings frame.
> 10. Select FileSave.
> 11. Deploy the application.
> 1. Select ToolsDeploy.
> 2. In the Connection Settings frame, enter the user name and password you specified when you installed the Application Server.
> 3. Click OK.

> To run the application, open the bookstore URL `http://localhost:8080/bookstore1/bookstore`.

> ### Troubleshooting

> The Duke's Bookstore database access object returns the following exceptions:

> - `BookNotFoundException`: Returned if a book can't be located in the bookstore database. This will occur if you haven't loaded the bookstore database with data by running `asant` `create-db_common` or if the database server hasn't been started or it has crashed.
> - `BooksNotFoundException`: Returned if the bookstore data can't be retrieved. This will occur if you haven't loaded the bookstore database with data or if the database server hasn't been started or it has crashed.
> - `UnavailableException`: Returned if a servlet can't retrieve the Web context attribute representing the bookstore. This will occur if the database server hasn't been started.

> Because we have specified an error page, you will see the message

>     The application is unavailable. Please try later.

> If you don't specify an error page, the Web container generates a default page containing the message

>     A Servlet Exception Has Occurred

> and a stack trace that can help you diagnose the cause of the exception. If you use `errorpage.html`, you will have to look in the server log to determine the cause of the exception.

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