How do I implement the business logic of a MVC in a seperate class from the Servlet? - servlets

Question

I have experimented putting the class in the servlets controller but I have trouble with the constructor and setting method access. I read its improves efficiency to have the business logic seperate, I even tried putting it in the JavaBean but I don't yet know how to send parameters from the controller to it. I still mave much to learn, just working on a project.

Answer 1

You can use EJB to separate business logic from Presentation tier i.e (Servlets and JSP) in JavaEE platform. If your project doesn't have much business logic code then simply use Java POJO classes. This example gives very raw idea. you can use web frameworks which have built in MVC design.
Controller:
Use Servlets to control navigation or perform other tasks against HTTP requests.
#WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public LoginServlet() {
super();
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
LoginManager loginManager=new LoginManager();
if(loginManager.isValidUser("getUserID from request Params","password from request params")){
//initialize user session and redirect to dashboard
//response.sendRedirect("/userhome.jsp");
}else{
//display failure messages. etc...
//response.sendRedirect("/login.jsp");
}
}
}
Model:
POJO which contains set of methods for login related operations.
public class LoginManager {
private Connection con;
public LoginManager() {
}
private void initConnection(){
//register driver class and create a new connection
//you can create separate DBUtils class to get new connections
//to prevent boilerplate code.
//make new connection to database
// con=..
}
private void closeConnection() throws SQLException{
con.close();
}
public boolean isValidUser(String user,String password) throws SQLException{
initConnection();
PreparedStatement pstm=con.prepareStatement("select 1 from users where userID = ? and password=?");
//set userID and password params
ResultSet rs=pstm.executeQuery();
if (rs.next()){
if(checkpassword.....)
return true;
}
closeConnection();
return false;
}
}
View:
pages like login.jsp and userhome.jsp pages are views;