Custom Tag - Beginning Java with WebSphere - page 380

Although the generated code is not very impressive, the variables and methods inherited from TagSupport will
make this class function as a tag. However, at least one inherited method has to overridden and coded to perform the
needed application functions.

The Tag Handler
As mentioned, CrtEmpBean inherits many methods from TagSupport . We will focus on the doStartTag and
doEndTag methods that are inherited from TagSupport . It was stated earlier that when the tag is encountered in the
JSP, the server runs the associated tag handler class. Specifically, when the start tag is encountered, the server runs the
doStartTag method and when the end tag is encountered, the doEndTag method is run.
In the example, we want the doStartTag method to:

A. Run EmpExtractor's getEmployeeInstance to create an Employee object from the request

B. Define the returned Employee object as a bean with a scope of request

Several things will be needed to do this. First, private variables of type Employee and EmpExtractor are
required. Second, the HttpServletRequest class needs to be imported into CrtEmpBean. This is required because
getEmployeeInstance is expecting an HttpServletRequest , but the request object is of type ServletRequest .
So, the ServletRequest object must be cast as an HttpServletRequest . Finally, we will be using the ever-helpful
PageContext object (provided by the server) to get the request and define the Employee object as a request bean
(or, said another way, define the Employee object as an attribute of the request).
The code to get the request object is:

pageContext.getRequest()

Because the returned request must be cast into an HttpServletRequest , this statement should be preceded with
the following to cast the request:

(HttpServletRequest)

This results in:

(HttpServletRequest)pageContext.getRequest()

Then the HttpServletRequest needs to be passed to EmpExtractor. Do this by embedding the above statement
in the method call as follows (where ee is the EmpExtractor variable):

ee.getEmployeeInstance(
(HttpServletRequest)pageContext.getRequest());

To define the returned Employee object as a request bean, we need to get the request again (using the page
context's getRequest method again). Then use the request's setAttribute method to define the employee object as a
bean called EmpBean. The statement to do that is as follows (where emp is the Employee variable):

pageContext.getRequest().setAttribute("EmpBean", emp);