java - Liferay : Java NullPointer exception

Question

我刚刚部署了我的第一个 liferay portlet，但该 portlet 似乎无法工作。这是我在控制台上遇到的错误(我也是 Java 开发和 Liferay 的新手!):

23:22:03,954 ERROR [http-bio-8080-exec-10][render_portlet_jsp:132] null
java.lang.NullPointerException
at me.hicham.portlet_view.Films.doEdit(Films.java:102)

在第 102 行我有:

        if(mode.equalsIgnoreCase("edit")) {...}

这是我的 Films.java :

package me.hicham.portlet_view;
import me.hicham.portlet_controller.Film;
import me.hicham.portlet_model.*;

import javax.portlet.ActionRequest;
import javax.portlet.PortletMode;
import javax.portlet.PortletURL;
import javax.portlet.RenderRequest;
import javax.portlet.ActionResponse;
import javax.portlet.RenderResponse;
import javax.portlet.PortletException;
import javax.portlet.WindowState;

import com.liferay.util.bridges.mvc.MVCPortlet;
import java.io.IOException;
import javax.portlet.PortletRequestDispatcher;


public class Films extends MVCPortlet {

public void doView(RenderRequest request, RenderResponse response)
        throws PortletException, IOException {

    String nomFilm = request.getParameter("nom");
    if (nomFilm == null ) {
        nomFilm="";
        }

    String listeFilm="";

    PortletURL renderURL = response.createRenderURL(); 
      renderURL.setPortletMode(PortletMode.VIEW);
      renderURL.setWindowState(WindowState.MAXIMIZED);
      renderURL.setWindowState(WindowState.NORMAL);

      listeFilm=listeFilm+"<div id=\"container\">";

      listeFilm=listeFilm+"<form name=\"input\" action=\""+renderURL+"\" method=\"POST\" class=\"zebra\">";
      listeFilm=listeFilm+"<table>";
      listeFilm=listeFilm+"<tr><td>Nom:</td><td><input type=\"text\" name=\"nom\" value=\""+nomFilm+"\"></td></tr>";
      listeFilm=listeFilm+"<tr><td></td><td><input type=\"submit\" value=\"Rechercher\"></td></tr>";
      listeFilm=listeFilm+"<table>";
      listeFilm=listeFilm+"</form> ";



    try {
        listeFilm=listeFilm+"\n<table  class=\"zebra\">";
        listeFilm=listeFilm+"\n<tr>";
        listeFilm=listeFilm+"\n<td></td><td>  Nom  </td><td>  Genre  </td><td>  Synopsis  </td><td>  Date Sortie  </td>";
        listeFilm=listeFilm+"\n</tr>";
        String ID="";
        for (Film film : MediaDAO.ListerTousLesFilms(nomFilm))
        {
            ID=String.valueOf(film.getId_film());
            PortletURL renderURL2 = response.createRenderURL(); 
              renderURL2.setPortletMode(PortletMode.EDIT);
              renderURL2.setWindowState(WindowState.MAXIMIZED);
              renderURL2.setWindowState(WindowState.NORMAL);   
              renderURL2.setParameter("mode","edit");
              renderURL2.setParameter("ID",ID);

            listeFilm=listeFilm+"\n<tr>";
            listeFilm=listeFilm+"\n<td><a href=\""+renderURL2+"\"><img src=\"http://localhost:8080/html/themes/classic/images/common/edit.jpg\" alt=\"Modifier\"/></a></td><td>"+film.getNom()+"</td><td>"+ MediaDAO.getGenre(film.getId_genre()).getLibelle()+"</td><td>"+film.getSynopsis()+"</td><td>"+film.getDateSortie()+"</td>";
            listeFilm=listeFilm+"\n</tr>";
        }
        listeFilm=listeFilm+"\n</table>";

        PortletURL renderURL2 = response.createRenderURL(); 
          renderURL2.setPortletMode(PortletMode.EDIT);
          renderURL2.setWindowState(WindowState.MAXIMIZED);
          renderURL2.setWindowState(WindowState.NORMAL);   
          renderURL2.setParameter("mode","add");
        listeFilm=listeFilm+"\n<a href=\""+renderURL2+"\"><img src=\"http://localhost:8080/html/themes/classic/images/common/ajout.jpg\" alt=\"Ajouter\"/></a>";
        listeFilm=listeFilm+"</div>";

    } catch (Exception e) {
        // TODO Auto-generated catch block
        listeFilm=listeFilm+e.getMessage();
    }
     request.setAttribute("att",listeFilm);
    response.setContentType("text/html");

    PortletRequestDispatcher dispatcher =
        getPortletContext().getRequestDispatcher("/WEB-INF/jsp/Films_view.jsp");
    dispatcher.include(request, response);

}


public void doEdit(RenderRequest request, RenderResponse response)
        throws PortletException, IOException {

    response.setContentType("text/html");
    String mode=request.getParameter("mode");
    request.setAttribute("att1", mode);

    if(mode.equalsIgnoreCase("edit"))
    {
        String chaineHTML=" ";
        try {

            String id_film="0";
            id_film =  request.getParameter("ID");
            Film film = MediaDAO.getFilm(id_film);
            chaineHTML=chaineHTML+"\n<table class=\"zebra\">";
            chaineHTML=chaineHTML+"\n<tr>";
            chaineHTML=chaineHTML+"\n<td colspan=\"2\">Modification</td>";
            chaineHTML=chaineHTML+"\n</tr>";


            chaineHTML=chaineHTML+"\n<tr><td><input type=\"hidden\" name=\"Mode\" value=\"edit\"><input type=\"hidden\" name=\"ID\" value=\""+film.getId_film()+"\">Nom :</td><td><input type=\"text\" name=\"Nom\" value=\""+film.getNom()+"\"></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td>Genre :</td><td><input type=\"text\" name=\"Genre\" value=\""+ MediaDAO.getGenre(film.getId_genre()).getLibelle()+"\"></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td>Synopsis :</td><td><input type=\"text\" name=\"Synopsis\" value=\""+film.getSynopsis()+"\"></td></tr>";
            //chaineHTML=chaineHTML+"\n<tr><td>Image :</td><td><input type=\"text\" name=\"Image\" value=\""+film.getImage()+"\"></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td>Date Sortie :</td><td><input type=\"text\" name=\"DateSortie\" value=\""+film.getDateSortie()+"\"></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td></td><td><input type=\"submit\" value=\"Valider\"></td></tr>";



            chaineHTML=chaineHTML+"\n</table>";
            chaineHTML=chaineHTML+"\n";

        } catch (Exception e) {
            // TODO Auto-generated catch block
            chaineHTML=chaineHTML+e.getMessage();
        }
         request.setAttribute("att",chaineHTML);

    }
    else
    {
        String chaineHTML="";
        try {
            chaineHTML=chaineHTML+"\n<table class=\"zebra\">";
            chaineHTML=chaineHTML+"\n<tr>";
            chaineHTML=chaineHTML+"\n<td colspan=\"2\">Insertion</td>";
            chaineHTML=chaineHTML+"\n</tr>";

            chaineHTML=chaineHTML+"\n<tr><td><input type=\"hidden\" name=\"Mode\" value=\"add\"><input type=\"hidden\" name=\"ID\" >Nom :</td><td><input type=\"text\" name=\"Nom\" ></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td>Genre :</td><td><input type=\"text\" name=\"Genre\" ></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td>Synopsis :</td><td><input type=\"text\" name=\"Synopsis\" ></td></tr>";
            //chaineHTML=chaineHTML+"\n<tr><td>Image :</td><td><input type=\"text\" name=\"Image\" ></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td>Date Sortie :</td><td><input type=\"text\" name=\"DateSortie\" ></td></tr>";
            chaineHTML=chaineHTML+"\n<tr><td></td><td><input type=\"submit\" value=\"Valider\"></td></tr>";



            chaineHTML=chaineHTML+"\n</table>";
            chaineHTML=chaineHTML+"\n";

        } catch (Exception e) {
            // TODO Auto-generated catch block
            chaineHTML=chaineHTML+e.getMessage();
        }
         request.setAttribute("att",chaineHTML);

    }
    PortletRequestDispatcher dispatcher =
        getPortletContext().getRequestDispatcher("/WEB-INF/jsp/Films_edit.jsp");
    dispatcher.include(request, response);

}

public void doHelp(RenderRequest request, RenderResponse response)
        throws PortletException, IOException {

    response.setContentType("text/html");

    PortletRequestDispatcher dispatcher =
        getPortletContext().getRequestDispatcher("/WEB-INF/jsp/Films_help.jsp");
    dispatcher.include(request, response);

}

public void processAction(ActionRequest request, ActionResponse response)
        throws PortletException, IOException {

    try
    {
        System.out.println("ProcessAction");
        String Mode = request.getParameter("Mode");
        if(Mode.equalsIgnoreCase("edit"))
        {
            String id_film = request.getParameter("ID");
            String Nom = request.getParameter("Nom");
            String Genre = request.getParameter("Genre");
            String Synopsis = request.getParameter("Synopsis");
            //String Image = request.getParameter("Image");
            String DateSortie = request.getParameter("DateSortie");
            System.out.println("begin....................");
            MediaDAO._Edit(id_film, Nom, Genre, Synopsis, DateSortie);
            System.out.println("end..................");
        }
        else
        {
            String Nom = request.getParameter("Nom");
            String Genre = request.getParameter("Genre");
            String Synopsis = request.getParameter("Synopsis");
            //String Image = request.getParameter("Image");
            String DateSortie = request.getParameter("DateSortie");
            System.out.println("begin....................");
            MediaDAO._Add( Nom, Genre, Synopsis, DateSortie);
            System.out.println("end..................");
        }
        response.setPortletMode(PortletMode.EDIT);
     }catch (Exception e) {

         e.printStackTrace();
         System.err.println("Process Action err "+e.getMessage());
}
        }

}

谢谢大家的帮助。

Answer 1

如果您不包含模式参数，这看起来会抛出 NPE。

String mode=request.getParameter("mode"); // This returns null if mode isn't set.
request.setAttribute("att1", mode);

if(mode.equalsIgnoreCase("edit")) // You can't call methods on a null object.

您可以在将模式与“编辑”进行比较之前检查模式是否为空，或者只是交换模式/“编辑”，因为“编辑”永远不会为空

if("edit".equalsIgnoreCase(mode))