Learn Java for Web Development

CHAPTER 3: Best Practices in Java EE Web Development 149

   Line 20: This line fetches all the initialization parameters from the deployment

descriptor.

   Line 22: This line adds these parameters to the response.

Listing 3-58 illustrates the configuration of the response filter in the deployment descriptor.

Listing 3-58. Configuring Simple Response Filter

1.
2.HTML5
3.com.apress.filters.ResponseHeaderFilter
4.
5.X-UA-Compatible
6.IE=edge,chrome=1
7.
8.
9.
10.HTML5
11./*
12.

   Line 5 to 6: These lines define the init parameters.

Front Controller

For web applications to be maintainable, all requests must pass through a common central
component. The lack of a centralized mechanism leads to the following problems:

   There is no centralized component for view management, which results in code

redundancy and code scattering across the views.

   Views are often encoded with view navigation logic. This results in intermingled

view content and view navigation.

The Front Controller pattern provides a centralized access for the request handling to provide
content retrieval, view management, navigation, validation, error handling, centralized security
control, and so on. The Front Controller pattern is best implemented with a servlet. Using a
centralized servlet to handle all requests and responses provides the following advantages:

   It provides a single location from which to control decisions related to

authentication and authorization.

   All URLs that the front controller is required to handle can be mapped to this

servlet.

   It provides a centralized access point to support the view management and

navigation.

   You can apply common logic to several views.

   It provides the separation of the presentation logic from the navigation and

business logic. This leads to loose coupling between the two.