向/从客户端/服务器发送对象

Question

我正在寻找错误的解决方案，该错误是在尝试将对象从服务器端发送到客户端时发生的。

单击JButton将创建形式为类实例的对象。 还将创建一个客户端类，该客户端类将对象传输到服务器。 不会发生任何错误。 但是，当将新对象发送回客户端时，将引发ClassCastException 。

ActionListener类别

class ActionHandler implements ActionListener {
   String buttonPressed;
   List<String> parameterList = new ArrayList<String>();

   public void actionPerformed(ActionEvent event) {
      if(event.getSource() == executeNameSearch) {
         buttonPressed = "NameSearch";
         parameterList = new ArrayList<String>();
         parameterList.add(pizzaNameSearch.getText());
         ObjectToServer object = new ObjectToServer(buttonPressed, parameterList);

         // build connection to server
         Client client = new Client();
         client.connectToServer(object);
      }
      else if(event.getSource() == executeNameSearch) {
         buttonPressed = "IDSuche";
         parameterList = new ArrayList<String>();
         parameterList.add(pizzaIDSearch.getText());
         ObjectToServer object = new ObjectToServer(buttonPressed, parameterList);

         Client client = new Client();
         client.connectToServer(object);
      }
      // some more actionPerformed cases..
   }
}

客户类

public class Client {
   public void connectToServer(ObjectToServer object) {
      Socket server = null;
      try {
         server = new Socket("localhost", 3141);
         ObjectOutputStream oos = new ObjectOutputStream(server.getOutputStream());
         ObjectInputStream ois = new ObjectInputStream(server.getInputStream());

         // sending object to server
         oos.writeObject(object);
         oos.flush();

         // receiving object from server
         try {
            // ERROR BY TRYING TO CAST HERE
            ObjectToClient objectIn = (ObjectToClient) ois.readObject();
         } catch (ClassNotFoundException e) {
            e.printStackTrace();
         }

         oos.close();
         ois.close();
      } catch(UnknownHostException e) {
         e.printStackTrace();
      } catch(IOException e) {
         e.printStackTrace();
      } finally {
         if(server!=null) {
            try {
               server.close();
            } catch(IOException e) {
               System.out.println(e);
            }
         }
      }
   }
}

服务器等级

public class Server {
   static PizzaManager manager = new PizzaManager();
   private static void handleConnection(Socket client) throws IOException {
      ObjectInputStream ois = new ObjectInputStream(client.getInputStream());
      ObjectOutputStream oos = new ObjectOutputStream(client.getOutputStream());

      ObjectToServer objectIn;
         try {
            objectIn = (ObjectToServer) ois.readObject();
            String buttonPressed = objectIn.getButtonPressed();

            if(buttonPressed.equals("NamenSuche")) {
               String searchedPizzaName = objectIn.getParameterList().get(0);
               manager.namenSuche(searchedPizzaName);

               ObjectToClient objectOut = new ObjectToClient();
               objectOut.setResults(manager.getResults());
               oos.writeObject(objectIn);
            }
            // some more cases..
         } catch (ClassNotFoundException e) {
            e.printStackTrace();
         }

         ois.close();
         oos.close();
   }

   public static void main(String[] args) throws IOException {
      ServerSocket server = new ServerSocket(3141);
      while(true) {
         Socket client = null;
         try {
            client = server.accept();
            handleConnection(client);
         }
         catch(IOException e) {
            e.printStackTrace();
         }
         finally {
            if(client!=null) {
                try {
                    client.close();
                }
                catch(IOException e) {
                }
            }
        }
      }
   }
}

堆栈跟踪

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: 
transfer.ObjectToServer cannot be cast to server.ObjectToClient
at client.Client.connectToServer(Client.java:34)
at gui.Pizzasuche$ActionHandler.actionPerformed(Pizzasuche.java:362)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

谢谢您的帮助！

Answer 1

我认为在您的Server类中，您尝试发送回错误的对象。 不应该是：

oos.writeObject(objectOut);

？

现在，您正在发送回objectIn ，它是一个ObjectToServer实例（或者至少是这样强制转换 ），而您正试图将其强制转换为ObjectToClient客户端，因此是ClassCastException。

固定服务器类：

public class Server {
   static PizzaManager manager = new PizzaManager();
   private static void handleConnection(Socket client) throws IOException {
      ObjectInputStream ois = new ObjectInputStream(client.getInputStream());
      ObjectOutputStream oos = new ObjectOutputStream(client.getOutputStream());

      ObjectToServer objectIn;
         try {
            objectIn = (ObjectToServer) ois.readObject();
            String buttonPressed = objectIn.getButtonPressed();

            if(buttonPressed.equals("NamenSuche")) {
               String searchedPizzaName = objectIn.getParameterList().get(0);
               manager.namenSuche(searchedPizzaName);

               ObjectToClient objectOut = new ObjectToClient();
               objectOut.setResults(manager.getResults());
               oos.writeObject(objectOut); // instead of objectIn
            }
            // some more cases..
         } catch (ClassNotFoundException e) {
            e.printStackTrace();
         }

         ois.close();
         oos.close();
   }

   public static void main(String[] args) throws IOException {
      ServerSocket server = new ServerSocket(3141);
      while(true) {
         Socket client = null;
         try {
            client = server.accept();
            handleConnection(client);
         }
         catch(IOException e) {
            e.printStackTrace();
         }
         finally {
            if(client!=null) {
                try {
                    client.close();
                }
                catch(IOException e) {
                }
            }
        }
      }
   }
}