客户端/服务器不接受ObjectInput和Output流

我有一个程序有两个服务器端进程。 一台服务器只是向客户端发送一个ArrayList。 另一台服务器首先从客户端获取一个字符串，然后找到与该ID对应的正确记录并将该记录发回。

我遇到了第二个服务器进程的问题。 请参阅下面的println语句，其中显示“卡在这里”。 这就是程序挂起的地方。

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 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(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 ID 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(); } } 

客户端：

  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 listModel = null; ArrayList 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(29); ArrayList custList = null; custList = (ArrayList) 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

您需要在两端的ObjectInputStream之前创建ObjectOutputStream。

Answer 2

您需要首先创建并刷新（）ObjectOutputStream，否则它会在尝试读取标头时卡住，另一端没有发送，因为它等待读取您的标头。