JSP pages can do the following:
Display data
Hold input data entered by users adding employees and editing employee data
Hold the code needed to process the actions of validating user credentials and adding, updating, and deleting employee records in the database
JSP pages are presented to users as HTML or XML. So, you can control the presentation of data in the same way as you do it for static HTML and XML pages. You can use standard HTML tags to format your page, including the title tag in the header to specify the title to be displayed for the page.
You use HTML tags for headings, tables, lists, and other items on your pages. Style sheets can also be used to define the presentation of items. If you use JDeveloper to develop your application, you can select styles from a list.
The following sections describe the main elements used in the JSP pages of the sample application:
JSP tags are used in the sample application in this guide for the following tasks: to initialize Java classes that hold the application methods and the JavaBean used to hold a single employee record, and to forward the user to either the same or another page in the application.
The jsp:useBean tag is used in pages to initialize the class that contains all the methods needed by the application, and the jsp:forward tag is used to forward the user to a specified page. You can drag the tags you need from the Component Palette of JSP tags, and enter the properties for the tag in the corresponding dialog box that is displayed.
Scriptlets are used to run the Java methods that operate on the database and to perform other processing in JSP pages. You can drag a scriptlet tag component from the Component Palette and drop it onto your page, ready to enter the scriptlet code. In JDeveloper, the code for scriptlets is entered in the Scriptlet Source Editor dialog box.
In this application, you use scriplets for a variety of tasks. As an example, one scriptlet calls the DataHandler method that returns a ResultSet object containing all the employees in the Employees table, which you can use to display that data in your JSP page. As another example, a scriplet is used to iterate through the same ResultSet object to display each item in a row of a table.
HTML tags are typically used for layout and presentation of the nondynamic portions of the user interface, for example headings and tables. In JDeveloper, you can drag and drop a Table component from the Component Palette onto your page. You must specify the number of rows and columns for the table, and all the table tags are automatically created.
HTML forms are used to interact with or gather information from the users on Web pages. The FORM element acts as a container for the controls on a page, and specifies the method to be used to process the form input.
For the filter control to select which employees to display, the employees.jsp page itself processes the form. For login, insert, edit, and delete operations, additional JSP pages are created to process these forms. To understand how the JSP pages in this application are interrelated, refer to Figure 1-2.
You can add a form in a JSP page by selecting it from the Component Palette of HTML tags. If you attempt to add a control on a page outside of the form component or in a page that does not contain a form, then JDeveloper prompts you to add a form component to contain it.