java - 在 ObjectInputStream 上调用 readObject() 时获取 java.io.EOFException

Question

我正在尝试在两个套接字之间实现简单的 UDP 通信。为了在 UDP 数据包中发送，需要将数据转换为字节数组。我创建了一个名为 Packet 的简单类，用于存储各种数据类型。此类实现 Serializable 接口(interface)，因此它可以转换为字节数组并通过 UDP 协议(protocol)发送。在我将 HashMap 对象放入 Packet 类之前，程序运行良好。将接收到的数据转换回 Packet 对象时，服务器端发生错误。

这是客户端代码:

package hr.fer.tel.rassus.udp.server;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.HashMap;    

public class UDPClient {

final static int PORT = 10001; // server port


/**
 * @param args the command line arguments
 */
public static void main(String args[]) throws IOException {


    HashMap<Integer, Integer> vector = new HashMap<Integer, Integer>();
    vector.put(1, 2);
    Packet p = new Packet(10000,10001,"co2",0,vector);
    byte[] serializedMessage = null;
    try {
            ByteArrayOutputStream bStream = new ByteArrayOutputStream();
            ObjectOutput oo = new ObjectOutputStream(bStream);
            oo.writeObject(p);
            serializedMessage = bStream.toByteArray();
            oo.close();
    } catch (Exception ex) {
            System.out.println("error "+ex.toString());
    }

    // determine the IP address of a host, given the host's name
    InetAddress address = InetAddress.getByName("localhost");

    // create a datagram socket and bind it to any available
    // port on the local host
    DatagramSocket socket = new DatagramSocket(); //SOCKET

    // create a datagram packet for sending data
    DatagramPacket packet = new DatagramPacket(serializedMessage, serializedMessage.length,
            address, PORT);

    // send a datagram packet from this socket
    socket.send(packet); //SENDTO
    socket.close(); //CLOSE
}
}

服务器代码:

package hr.fer.tel.rassus.udp.server;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.util.logging.Level;
import java.util.logging.Logger;




public class UDPServer {

final static int PORT = 10001; // server port

/**
 * @param args the command line arguments
 */
public static void main(String args[]) throws IOException {

    byte[] rcvBuf = new byte[256]; // received bytes

    // create a UDP socket and bind it to the specified port on the local
    // host
    DatagramSocket socket = new DatagramSocket(PORT); //SOCKET -> BIND

    while (true) { 
        // create a DatagramPacket for receiving packets
        DatagramPacket packet = new DatagramPacket(rcvBuf, rcvBuf.length);

        // receive packet
        socket.receive(packet); //RECVFROM

        // construct a new String by decoding the specified subarray of
        // bytes
        // using the platform's default charset
        ObjectInputStream iStream;
        Packet p = null;


        try {
            iStream = new ObjectInputStream(new ByteArrayInputStream(packet.getData()));
            p = (Packet) iStream.readObject();
            iStream.close();
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(UDPServer.class.getName()).log(Level.SEVERE, null, ex);
        }



    }
}
}

数据包类:

package hr.fer.tel.rassus.udp.server;

import java.io.Serializable;
import java.util.ArrayList; 
import java.util.HashMap;
import java.util.Set;

/**
 *
 * @author adrianzgaljic
 */
public class Packet implements Serializable{



private int fromPort;
private int toPort;
private String co2;
private boolean flag;
private long timeStamp;
private HashMap<Integer, Integer> vector;
Set<Integer> keys;



public Packet(int from, int to, String co2, long time, HashMap<Integer, Integer> vector){

    this.fromPort = from;
    this.toPort = to;
    this.co2= co2;
    this.timeStamp = time;
    this.vector = vector;
    flag = false;

}

public Packet(int from){
    this.fromPort = from;
    this.flag = true;
}

    public int getFromPort() {
    return fromPort;
}

public int getToPort() {
    return toPort;
}

public String getCo2() {
    return co2;
}

public long getTimeStamp() {
    return timeStamp;
}

public boolean isFlag() {
    return flag;
}

public HashMap<Integer, Integer> getVector() {
    return vector;
} 



}

堆栈跟踪:

Exception in thread "main" java.io.EOFException
at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2325)
at java.io.ObjectInputStream$BlockDataInputStream.readUTFBody(ObjectInputStream.java:3063)
at java.io.ObjectInputStream$BlockDataInputStream.readUTF(ObjectInputStream.java:2864)
at java.io.ObjectInputStream.readUTF(ObjectInputStream.java:1072)
at java.io.ObjectStreamClass.readNonProxy(ObjectStreamClass.java:704)
at java.io.ObjectInputStream.readClassDescriptor(ObjectInputStream.java:830)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1601)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1517)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1771)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1990)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1915)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1798)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
at hr.fer.tel.rassus.udp.server.UDPServer.main(UDPServer.java:48)
Java Result: 1

Answer 1

运行您的代码后，我意识到我之前的回答并没有解决问题，但是我会把它和新的一起留下，因为它描述了一个可能导致类似效果的问题。

新答案:

您的服务器的数据报数据包太小，无法接收您发送的所有数据，请通过增加缓冲区大小来增加其大小:

byte[] rcvBuf = new byte[256]; // received bytes

例如新字节[2048]

旧答案:

在客户端交换这两行:

serializedMessage = bStream.toByteArray();
oo.close();

所以你应该有这个:

oo.close();
serializedMessage = bStream.toByteArray();

您的代码的问题在于您正在获取字节，而 ObjectOutputStream 实际上并未将所有数据刷新到您的 ByteArrayOutputStream。