student-tracker app bug fixes

StudentControllerServlet.java

package com.luv2code.web.jdbc;

import java.io.IOException;
import java.util.List;

import javax.annotation.Resource;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sql.DataSource;

/**
 * Servlet implementation class StudentControllerServlet
 */
@WebServlet("/StudentControllerServlet")
public class StudentControllerServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
	
	private StudentDbUtil studentDbUtil;
	
	@Resource(name="jdbc/web_student_tracker")
	private DataSource dataSource;

	@Override
	public void init() throws ServletException {
		// TODO Auto-generated method stub
		super.init();
		try{
		studentDbUtil = new StudentDbUtil(dataSource);
		}
		catch(Exception ex){
			throw new ServletException(ex);
		}
	}



	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String theCommand = request.getParameter("command");
		
		// if the command is missing, then default to listing students
		if (theCommand == null) {
			theCommand = "LIST";
		}
		
		switch (theCommand) {
		case "LIST":
			listStudents(request,response);
			break;
		
		case "ADD":
			try {
				addStudents(request,response);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			break;
			
		case "LOAD":
			try {
				loadStudents(request,response);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			break;
			
		case "UPDATE":
			try {
				updateStudents(request,response);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			break;
			
		default:
			listStudents(request,response);
			break;
		}
		
	}



	private void updateStudents(HttpServletRequest request, HttpServletResponse response) throws Exception {
		// TODO Auto-generated method stub
		int id = Integer.parseInt(request.getParameter("studentId"));
		String firstName = request.getParameter("firstName");
		String lastName = request.getParameter("lastName");
		String email = request.getParameter("email");
		
		Student theStudent = new Student(id, firstName, lastName, email);
		studentDbUtil.updateStudent(theStudent);
		listStudents(request, response);
	}



	private void loadStudents(HttpServletRequest request, HttpServletResponse response) throws Exception {
		// TODO Auto-generated method stub
		String theStudentId = request.getParameter("studentId");
		Student theStudent = studentDbUtil.getStudent(theStudentId);
		request.setAttribute("THE_STUDENT", theStudent);
		RequestDispatcher theDispatcher = request.getRequestDispatcher("/update-student-form.jsp");
		theDispatcher.forward(request, response);
	}



	private void addStudents(HttpServletRequest request, HttpServletResponse response) throws Exception {
		// TODO Auto-generated method stub
		String firstName = request.getParameter("firstName");
		String lastName = request.getParameter("lastName");
		String email = request.getParameter("email");
		
		Student theStudent = new Student(firstName, lastName, email);
		
		studentDbUtil.addStudent(theStudent);
		
		listStudents(request, response);
	}



	private void listStudents(HttpServletRequest request, HttpServletResponse response) {
		try {
			List<Student> students = studentDbUtil.getStudents();
			
			System.out.println("students:" + students);
			
			request.setAttribute("STUDENT_LIST", students);
			
			RequestDispatcher dispatcher = request.getRequestDispatcher("/list-students.jsp");
			dispatcher.forward(request, response);
			
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>web-student-tracker</display-name>
  <welcome-file-list>  
    <welcome-file>StudentControllerServlet</welcome-file>
   <welcome-file>index.html</welcome-file>  
  </welcome-file-list>
</web-app>