试图通过套接字发送arrayList,在对象输入流初始化(客户端)处获取空指针异常。当通过套接字接收数组列表时发生NullPointerException
客户:
try {
ObjectInputStream objIn = new ObjectInputStream(
Client.socket.getInputStream()); // HERE
library = (ArrayList<Book>) objIn.readObject();
} catch (IOException e) {
服务器:
try {
ObjectOutputStream objOut = new ObjectOutputStream(
this.client.getOutputStream());
objOut.writeObject(library);
objOut.flush(); // added later, not helping
}
我一直在努力,现在几乎没有成功comunicate通过套接字两天。我不知道发生了什么事。 Ofc我计划更好地记录自己,当我有更多的时间,但现在我真的很想知道发生了什么。
编辑
public class Client {
private static int port = 6666;
private static Socket socket = null;
public Client (int port) {
Client.port = port;
}
public Client() {
}
public void establishConnection() {
try {
Client.socket = new Socket(InetAddress.getByName(null), Client.port);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
服务器:
public void start() {
(new Thread() {
public void run() {
try {
Server.socket = new ServerSocket(Server.portNumber);
while (!Server.stop) {
Socket client = Server.socket.accept();
(new HandleRequest (client)).start();
}
...............
public class HandleRequest extends Thread {
private Socket client = null;
private SQL sql_db = new SQL();
public HandleRequest (Socket client) {
this.client = client;
}
@Override
public void run() {
try {
if (!this.sql_db.isConnected())
this.sql_db.connect();
if (this.client == null) {
System.out.println("Error: client does not exist, NO idea what's going on");
return;
}
ArrayList<Book> library = this.sql_db.getAllBooks();
try {
ObjectOutputStream objOut = new ObjectOutputStream(
this.client.getOutputStream());
objOut.writeObject(library);
objOut.flush();
} catch (Exception e) {
System.out.println("Server error in handling request for whole library!");
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
没有足够的代码在这个问题上给你答案。请告诉我们'Client.socket'的定义和实例。最好张贴证明问题的[SSCCE](http://sscce.org)。 –
您可以提供堆栈跟踪并显示其投诉的行号吗?这通常在这些情况下非常有用。 – CodeChimp
@Duncan Ok会尝试。 @CodeChimp,堆栈跟踪在我的代码中指向'// here' – Kalec