在ObjectInputStream上調用readObject（）時獲取java.io.EOFException

Question

我試圖在兩個套接字之間實現簡單的UDP通信。 為了在UDP包中發送，需要將數據轉換為字節數組。 我創建了一個名為Packet的簡單類，用於存儲各種數據類型。 此類實現Serializable接口，因此可以將其轉換為字節數組並通過UDP協議發送。 程序工作正常，直到我把HashMap對象放在Packet類中。 當將已傳送的數據轉換回Packet對象時，服務器端出錯。

這是客戶端代碼：

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
}
}

服務器代碼：

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);
        }



    }
}
}

包類：

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;
} 



}

堆棧跟蹤：

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

在運行你的代碼后，我意識到我之前的答案並沒有解決問題，但是我將把它與新的一起留下，因為它描述了一個可能導致類似效果的問題。

新答案：

您的服務器的數據報包大小太小，無法接收您發送的所有數據，通過增加緩沖區大小來增加其大小：

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

例如new byte[2048]

老答案：

在客戶端中交換這兩行：

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

所以你應該這樣：

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

您的代碼的問題在於您獲取字節，而ObjectOutputStream實際上並未將所有數據刷新到ByteArrayOutputStream 。