Объектно-выходные и выходные потоки не принимаются клиентом/сервером

Question

У меня есть одна программа с двумя процессами с серверами. Один сервер просто отправляет клиенту ArrayList. Другой сервер сначала берет строку из клиента, а затем находит соответствующую запись, соответствующую идентификатору, и отправляет запись обратно.

У меня проблемы со вторым процессом сервера. См. Инструкцию println ниже, где говорится: «Застрял здесь». Вот где программа зависает.

import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.net.ServerSocket; 
import java.net.Socket; 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.ResultSet; 
import java.sql.Statement; 
import java.util.ArrayList; 


public class CustServer{ 
    public static void main(String args[]) throws IOException, ClassNotFoundException{ 
    ServerSocket serverSocket1 = null; 
    ServerSocket serverSocket2 = null; 
    ArrayList<Customer> list = null; 

     String driverName = "sun.jdbc.odbc.JdbcOdbcDriver"; 
     String connectionURL = "jdbc:odbc:customer"; 
     Connection con = null; 
     Statement stmt = null; 
     String sqlStatement = "SELECT ID, CustomerName, Address," + 
       " City, State, Zip, Orders FROM Customer"; 
     ResultSet rs = null; 
     try { 
      Class.forName(driverName).newInstance(); 
      con = DriverManager.getConnection(connectionURL); 
      stmt = con.createStatement(); 
      rs = stmt.executeQuery(sqlStatement); 
      list = new ArrayList<Customer>(39); 
      while(rs.next()){ 
       list.add(
        new Customer(
         rs.getString(1), 
         rs.getString(2), 
         rs.getString(3), 
         rs.getString(4), rs.getString(5), rs.getString(6), 
         rs.getString(7))); 
      } 

      rs.close(); 
      stmt.close(); 
      con.close(); 
     }catch (Exception ex) { ex.printStackTrace(); } 

    try { 
     serverSocket1 = new ServerSocket(8889); 
     System.out.println("Customer DB server is running at port 8889"); 

    } catch (IOException e){ 
     System.out.println("Could not listen on port: 8889."); 
     System.exit(1); 
    } 

    Socket clientSocket = null; 
    try{ 
     clientSocket = serverSocket1.accept(); 

    }catch (IOException e){ 
     System.out.println("Server 1: Accept failed."); 
     System.exit(1); 
    } 
    //A server program which returns a list of customer IDs from the database. 
    ObjectOutputStream out = new ObjectOutputStream(clientSocket.getOutputStream()); 
    out.writeObject(list); 
    System.out.println(list.size() + "Customer IDs (list) were sent."); 

    out.flush(); 
    out.close(); 
    clientSocket.close(); 
    serverSocket1.close(); 
    //second server process: 
    //Takes a customer I D and returns the customer record 
    try { 
     serverSocket2 = new ServerSocket(8888); 
     System.out.println("Customer DB server is running at port 8888"); 

    } catch (IOException e){ 
     System.out.println("Could not listen on port: 8889."); 
     System.exit(1); 
    } 
    try{ 
     clientSocket = serverSocket2.accept(); 

    }catch (IOException e){ 
     System.out.println("Server 2: Accept failed."); 
     System.exit(1); 
    } 

    System.out.println("Gets stuck here."); //<<<<<HERE 
    ObjectInputStream in = new ObjectInputStream(clientSocket.getInputStream()); 
    ObjectOutputStream out1 = new ObjectOutputStream(clientSocket.getOutputStream()); 
    String id = (String) in.readObject(); 
    String record = null; 

    for(Customer c : list){ 
     if(c.getID().equals(id)) 
      record = c.toString(); 
    } 

    out1.writeObject(record); 

    out1.flush(); 
    out1.close(); 
    in.close(); 
    clientSocket.close(); 
    serverSocket2.close(); 
    } 
} 

клиентской:

import java.awt.BorderLayout; 
import java.awt.Dimension; 
import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.net.Socket; 
import java.net.UnknownHostException; 
import java.util.ArrayList; 

import javax.swing.DefaultListModel; 
import javax.swing.JFrame; 
import javax.swing.JList; 
import javax.swing.JPanel; 
import javax.swing.JScrollPane; 
import javax.swing.JTextField; 
import javax.swing.event.ListSelectionEvent; 
import javax.swing.event.ListSelectionListener; 


public class ClientGUI extends JFrame implements ListSelectionListener{ 

    //gui components 
    JList jlist = null; 
    String requestID = null; //Assigned to selected ID in JList. 
    JScrollPane scpane = null; 
    JTextField field = null; 
    JPanel pane = null; 
    DefaultListModel<String> listModel = null; 
    ArrayList<String> idList = null; 

    //client stuff: 
    Socket sock1 = null; 
    Socket sock2 = null; 
    ObjectInputStream in = null; 
    ObjectOutputStream out = null; 

    public ClientGUI() throws ClassNotFoundException{ 
     //get List of IDs from Server1 
     try{ 
      sock1 = new Socket("FahadAhmed-PC", 8889); 
      in = new ObjectInputStream(sock1.getInputStream()); 
      idList = new ArrayList<String>(29); 
      ArrayList<Customer> custList = null; 
      custList = (ArrayList<Customer>) in.readObject(); 
      for(Customer c : custList){ 
       idList.add(c.getID()); 
      } 

      in.close(); 
      sock1.close(); 

      sock2 = new Socket("FahadAhmed-PC", 8888); 



     }catch(UnknownHostException e) { 
      System.err.println("Don't know about host: FahadAhmed-PC"); 
      System.exit(1); 
     }catch(IOException e){ 
      System.err.println(e); 
      System.exit(1); 
     } 

     //Setup GUI 
     jlist = new JList(idList.toArray()); 
     jlist.setVisibleRowCount(10); 
     scpane = new JScrollPane(jlist); 
     jlist.addListSelectionListener(this); 
     pane = new JPanel(new BorderLayout()); 
     pane.setPreferredSize(new Dimension(300, 300)); 
     field = new JTextField(29); 
     field.setEditable(false); 
     pane.add(scpane, BorderLayout.PAGE_START); 
     pane.add(field, BorderLayout.PAGE_END); 

     this.setContentPane(pane); 
     this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     this.pack(); 
     this.setVisible(true); 
    } 

    public static void main(String args[]) throws ClassNotFoundException{ 
     ClientGUI gui = new ClientGUI(); 
    } 


    @Override 
    public void valueChanged(ListSelectionEvent arg0) { 
     if(!arg0.getValueIsAdjusting()) 
      try { 
       getRecord(jlist.getSelectedValue().toString()); 
      } catch (ClassNotFoundException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      }  
    } 

    private void getRecord(String getID) throws ClassNotFoundException { 
     try{ 
      in = new ObjectInputStream(sock2.getInputStream()); 
      out = new ObjectOutputStream(sock2.getOutputStream()); 
      System.out.println(getID + "sent to getRecord method"); 
      out.writeObject(getID); 

      String rec = (String) in.readObject(); 

      field.setText(rec); 
      out.flush(); 
      out.close(); 
      in.close(); 
     }catch(UnknownHostException e) { 
      System.err.println("Don't know about host: FahadAhmed-PC"); 
      System.exit(1); 
     }catch(IOException e){ 
      System.err.println(e); 
      System.exit(1); 
     } 
    } 


} 

Answer 1

Вам необходимо создать ObjectOutputStream перед ObjectInputStream с обоих концов.

Answer 2

Вам нужно создать и флеш() для ObjectOutputStream первый, или он будет застревать пытается прочитать заголовок, другой конец не послал, потому что его ожидания в прочитайте свой заголовок.