siw-jpa-es2-controllerInserimentoClass

package controller;
import java.io.IOException;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
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 helper.HelperInserimentoProdotto;
import action.ActionInserimentoProdotto;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;

/**
 * Servlet implementation class Controller
 */
@WebServlet("/controllerInserimento")
public class ControllerInserimento extends HttpServlet {
private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public ControllerInserimento() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //response.getWriter().append("Served at: ").append(request.getContextPath());
        String nextPage = "/inserimentoProdotto.jsp";
        ServletContext servletContext = getServletContext();
        RequestDispatcher rd = servletContext.getRequestDispatcher(nextPage);
        rd.forward(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("products-unit");
        EntityManager em = emf.createEntityManager(); //è una classe che gestisce le entità

        HelperInserimentoProdotto helper = new HelperInserimentoProdotto();
        ActionInserimentoProdotto action = new ActionInserimentoProdotto();

        String nextPage = "/InserimentoProdotto.jsp";
        if(helper.validate(request, response)){
            nextPage = action.execute(request, emf);
        }
        nextPage = response.encodeURL(nextPage);
        ServletContext servletContext = getServletContext();
        RequestDispatcher rd = servletContext.getRequestDispatcher(nextPage);
        rd.forward(request, response);
    }

}



----------------------------------------------------ERRORE------------------------------------------------------------------------

mag 20, 2016 6:43:09 PM org.apache.catalina.startup.Catalina start
INFORMAZIONI: Server startup in 8342 ms
mag 20, 2016 6:43:12 PM org.apache.catalina.core.StandardWrapperValve invoke
GRAVE: Servlet.service() for servlet [controller.ControllerInserimento] in context with path [/siw-jpa-es2] threw exception [Servlet execution threw an exception] with root cause
java.lang.ClassNotFoundException: javax.persistence.Persistence
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1858)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1701)
    at controller.ControllerInserimento.doPost(ControllerInserimento.java:52)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)