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Front controller design pattern provides a centralized control to handle all the requests so that all the requests can be handled by a single handler. This handler can perform these tasks like authentication/ authorization/ tracking or logging of request and then pass the requests to corresponding handlers. Following are the components used in this pattern:
Front Controller- Single handler for all type of request coming to the application (web based/ desktop based).
Dispatcher- Front Controller may use a dispatcher object which is responsible to dispatch the request to corresponding specific handler.
View- Views are the object for which the requests are made.
Implementation:
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We´re going to create a FrontController that is Dispatcher to act as Front Controller and Dispatcher correspondingly. HomeView and StudentView represent are views for which requests can come to front controller. Following is the flow diagram of FrontController design pattern.
Example of Front controller design pattern:
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******************************** Step 1- Create Views ********************************
HomeView.java:
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public class HomeView {
public void show(){
System.out.println("Displaying Home Page");
}
}
StudentView.java:
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public class StudentView {
public void show(){
System.out.println("Displaying Student Page");
}
}
******************************** Step 2- Create Dispatcher ********************************
Dispatcher.java:
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public class Dispatcher {
private StudentView studentView;
private HomeView homeView;
public Dispatcher(){
studentView = new StudentView();
homeView = new HomeView();
}
public void dispatch(String request){
if(request.equalsIgnoreCase("STUDENT")){
studentView.show();
}else{
homeView.show();
}
}
}
****************************** Step 3- Create FrontController ******************************
Context.java:
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public class FrontController {
private Dispatcher dispatcher;
public FrontController(){
dispatcher = new Dispatcher();
}
private boolean isAuthenticUser(){
System.out.println("User is authenticated successfully.");
return true;
}
private void trackRequest(String request){
System.out.println("Page requested: " + request);
}
public void dispatchRequest(String request){
//log each request
trackRequest(request);
//authenticate the user
if(isAuthenticUser()){
dispatcher.dispatch(request);
}
}
}
********* Step 4- Use the FrontController to demonstrate Front Controller Design Pattern *********
FrontControllerPatternDemo.java
public class FrontControllerPatternDemo {
public static void main(String[] args) {
FrontController frontController = new FrontController();
frontController.dispatchRequest("HOME");
frontController.dispatchRequest("STUDENT");
}
}
********************************* Step 5- Verify the output *********************************
Page requested: HOME
User is authenticated successfully.
Displaying Home Page
Page requested: STUDENT
User is authenticated successfully.
Displaying Student Page
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