java - 检查套接字发送的对象类型时，服务器未接收到对象

Question

我想检查发送到服务器的对象类型，因为有两种类型的客户端发送对象，一种是汽车司机，另一种是行人。但是每当我使用 if(datain.readObject() instanceof Pedestrian or CarDriver) 时，服务器不会收到任何对象，也不会再向客户端发送任何响应。这是我的代码:服务器

package eece350;
import java.io.*;
import java.net.Socket;
import java.net.ServerSocket;
import java.sql.Array;
import java.util.ArrayList;
import java.util.Scanner;
import java.lang.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.sql.*;
/**
*
* @author user
*/ 
public class SkillsServer {
private ServerSocket serverSocket;
private void acceptConnections() {
try {
        int port = 7171;
        serverSocket = new ServerSocket(port);
    } 
catch (IOException e) 
    {
        System.err.println("ServerSocket instantiation failure");
        e.printStackTrace();
        System.exit(0);
}
// Entering the infinite loop
while (true) {
                    try {
                        // wait for a TCP handshake initialization (arrival 
of a "SYN"
                        // packet)
            Socket newConnection = serverSocket.accept();
            System.out.println("accepted connection");
            // Now, pass the connection socket created above to a thread and
            // run it in it
            // First create the thread and pass the connection socket to it
            // This is a non-blocking function: constructor of the class
            // ServerThread
            ServerThread st = new ServerThread(newConnection);
            // Then, start the thread, and go back to waiting for another
            // TCP connection
            // This also is not blocking
            new Thread(st).start();
        } 
                    catch (IOException ioe)
                    {
                        System.err.println("server accept failed");
        }
    }
}
public static void main(String[] args) throws NullPointerException, 
ClassNotFoundException, FileNotFoundException, SQLException 
{
    SkillsServer server = null;
    server= new SkillsServer();
    // call this function, which will start it all...
    server.acceptConnections();
}
// Internal class
class ServerThread implements Runnable
{
    private Socket socket;
    private ObjectInputStream datain;
    private ObjectOutputStream dataout;
            private DataOutputStream outToClient;
    ServerThread(Socket socket) 
            {
        // Inside the constructor: store the passed object in the data
        // member
        this.socket = socket;
    }
    public void run() 
    {
    try 
    {
// Input and output streams, obtained from the member socket
// object
         outToClient = new DataOutputStream(new 
BufferedOutputStream(socket.getOutputStream()));
         datain = new ObjectInputStream(new 
BufferedInputStream(socket.getInputStream()));
        //dataout = new ObjectOutputStream(new 
BufferedOutputStream(socket.getOutputStream()));
    } 
    catch (IOException e) 
    {
        return;
    }
        String name="";
        Coordinates location;
        Coordinates Destination;
        int numberofPassenger;
        double chargingPerKilometer;
        int carCapacity,did;
        Regulations regulations;
        boolean connectionActive = true;
        String reply=""; 
        while (connectionActive) 
        {
            try 
            {
                if(datain.readObject().getClass()==CarDriver.class)
                {

                    String url 
="jdbc:sqlserver://localhost:1433"+";databaseName=EECE350Project;Integrated 
Security=True";
                    String userName = "Mahdi";
                    String password = "admin";

Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
                    Connection conn = 
DriverManager.getConnection(url,userName,password);
                    Statement stmt = conn.createStatement();
                    CarDriver CarDriver1 = (CarDriver)datain.readObject();
                    name=CarDriver1.getName();
                    location=CarDriver1.getLocation();
                    Destination=CarDriver1.getDestination();
                    numberofPassenger=CarDriver1.getNumofPassengers();

chargingPerKilometer=CarDriver1.getChargingPerKilometer();
                    carCapacity = CarDriver1.getCarCapacity();
                    regulations = CarDriver1.getRegulations();
                    did=CarDriver1.getDid();
                    reply = "I recieved your connection"+name;
                    outToClient.write(reply.getBytes(),0,reply.length());
                    outToClient.write("\\n".getBytes(),0,1);
                    outToClient.flush();
                        try
                        {
                            System.out.println("Closing Socket");
                            datain.close();
                            outToClient.close();
                            socket.close();
                        }
                        catch(IOException ioe)
                        {
                            System.out.println("Unable to Close Socket");          
                        }
                    //String query = "Insert Into EECE 350Project 
values(name='"+name+"',did="+did+",XLocation="+location.coordinateX+")";
                } 
                else 
                {
                    System.out.println("Hey");
                    Regulations Pedregulations;
                    int pid=0;
                    Coordinates Pedlocation;
                    Coordinates PedDestination;
                    Pedestrian Pedestrian1 = (Pedestrian) 
datain.readObject();
                    pid = Pedestrian1.pid;
                    Pedlocation = Pedestrian1.currentLocation;
                    PedDestination = Pedestrian1.Destination;
                    reply= "I recieved your connection";
                    System.out.println(pid);
                    outToClient.write(reply.getBytes(),0,reply.length());
                    outToClient.write("\\n".getBytes(),0,1);
                    outToClient.flush();
                        //outToClient.writeBytes(reply);
                        try
                        {
                            System.out.println("Closing Socket");
                            datain.close();
                            outToClient.close();
                            socket.close();
                        }
                        catch(IOException ioe)
                        {
                            System.out.println("Unable to Close Socket");          
                        }
                    }
            }            
            catch (IOException ex) 
            {

Logger.getLogger(SkillsServer.class.getName()).log(Level.SEVERE, null, ex);
            } 
            catch (ClassNotFoundException ex) 
            {

Logger.getLogger(SkillsServer.class.getName()).log(Level.SEVERE, null, ex);
            } 
            catch (SQLException ex) 
            {

Logger.getLogger(SkillsServer.class.getName()).log(Level.SEVERE, null, ex);
            } 
        }

            try 
            {
    System.out.println("closing socket");
    datain.close();
    dataout.close();
    socket.close();
            } 
                catch (IOException e) 
                    {
                        System.out.print('.');
                    }
            }
        }
    }

客户端代码:例如行人

package eece350;
import java.io.Serializable;
import java.io.*; 
import java.net.*;
/**
 *
 * @author user
 */
public class Pedestrian implements Serializable 
{
  public int pid=0;
  public Coordinates currentLocation;
  public Coordinates Destination;
  public Regulations preferences;
  public Pedestrian(Coordinates currentLocation,Coordinates Destination,int 
 pid,Regulations preferences)
 {
    this.pid=pid;
    this.Destination=Destination;
    this.currentLocation=currentLocation;
    this.preferences=preferences;
}
public static void main(String argv[]) throws Exception
{
    Socket clientSocket = new Socket("localhost", 7171); 
    ObjectOutputStream outToServer = new 
ObjectOutputStream(clientSocket.getOutputStream());
    BufferedReader inFromServer = new BufferedReader(new 
InputStreamReader(clientSocket.getInputStream()));
    //ObjectInputStream inFromServer = new 
ObjectInputStream(clientSocket.getInputStream()); 
    int pid =0;
    double XLocation = 2;
    double YLocation = 2;
    double XDestination = 4;
    double YDestination = 4;
    String modifiedSentence = "";
    Coordinates currentLocation = new Coordinates(XLocation,YLocation);
    Coordinates Destination = new Coordinates(XDestination,YDestination);
    Regulations regulations = new Regulations("yes","No","yes","No");
    Pedestrian pedestrian1 = new 
Pedestrian(currentLocation,Destination,pid,regulations);
    outToServer.writeObject(pedestrian1);
    modifiedSentence = inFromServer.readLine();
    System.out.println("FROM SERVER: " + modifiedSentence);
    outToServer.close();
    inFromServer.close();
    outToServer.flush();
    clientSocket.close();

 }
}

请有人帮助我:(

Answer 1

实际上，您调用了 readObject() 两次(但流上只有一个对象)。

问题从这里开始:

if(datain.readObject().getClass()==CarDriver.class)

通过此调用，您将消耗该对象，但不会使用它。然后您再次调用 readObject()，它需要另一个对象(但不存在)。

替换为:

Object object = datain.readObject();  // Read it once
if(object.getClass()==CarDriver.class) { 
    CarDriver carDriver1 = (CarDriver)object;
    // process carDriver1;
}
else {
    Pedestrian pedestrian1 = (Pedestrian)object; 
    // process pedestrian1
}

你尝试过吗:

Object object = datain.readObject();
if (object instanceof CarDriver) {
   CarDriver carDriver1 = (CarDriver)object;
   // process carDriver1;
}
else if (object instanceof Pedestrian) {
    Pedestrian pedestrian1 = (Pedestrian)object; 
    // process pedestrian1
}  

编辑:

替换这个:

Pedestrian Pedestrian1 = (Pedestrian)datain.readObject();

与:

Pedestrian Pedestrian1 = (Pedestrian)object;