我编写了一个小程序，它打开一个 UDP 套接字并接收一些 UDP 数据包。我尝试的是每个数据包都由自己的线程使用 fork-join 处理（更改字节顺序），然后通过 udp 将更改的数据包转发到另一个系统。
这是代码：
package cwstreamswitcher;
import java.io.IOException;
import java.net.*;
import java.util.concurrent.*;
import java.util.logging.Level;
import java.util.logging.Logger;
public class CwStreamSwitcher {
public class Switch extends RecursiveAction {
private byte[] mMessage;
DatagramSocket mSocket;
public Switch(DatagramSocket serverSocket) throws UnknownHostException, IOException {
// mMessage = message;
mSocket = serverSocket;
int cwPort = 51001;
String host = "localhost";
byte[] receiveData = new byte[33];
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
StringBuilder sb = new StringBuilder(); //
for (byte b : receiveData) { //
sb.append(String.format("%02X ", b)); //just for checking the data , will be removed in final version
} //
System.out.println("Received: " + sb.toString()); //
byte[] newCache = new byte[29];
newCache[0] = (byte) 0x02;
System.arraycopy(receiveData, 32, newCache, 1, 1);
System.arraycopy(receiveData, 1, newCache, 2, 2);
byte onid = receiveData[7];
switch (onid) {
case (byte) 0x6d:
newCache[4] = (byte) 0x03;
newCache[5] = (byte) 0x6e;
break;
case (byte) 0x08:
newCache[4] = (byte) 0x08;
newCache[5] = (byte) 0x00;
break;
case (byte) 0x3f:
newCache[4] = (byte) 0x01;
newCache[5] = (byte) 0x3e;
break;
case (byte) 0x01:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x01;
break;
case (byte) 0x04:
newCache[4] = (byte) 0xfb;
newCache[5] = (byte) 0xff;
break;
case (byte) 0xab:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0xab;
break;
case (byte) 0x56:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x56;
break;
case (byte) 0x02:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x02;
break;
case (byte) 0x7e:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x7e;
break;
case (byte) 0x06:
newCache[4] = (byte) 0x06;
newCache[5] = (byte) 0x00;
break;
case (byte) 0x85:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x85;
break;
case (byte) 0x71:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x71;
break;
case (byte) 0x46:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x46;
break;
default:
newCache[4] = (byte) 0x00;
newCache[5] = (byte) 0x85;
}
newCache[6] = (byte) 0x06;
newCache[7] = (byte) 0x04;
System.arraycopy(receiveData, 12, newCache, 8, 4);
newCache[12] = (byte) 0x01;
System.arraycopy(receiveData, 16, newCache, 13, 16);
//send the converted data
DatagramPacket response = new DatagramPacket(newCache, newCache.length, InetAddress.getByName(host), cwPort);
mSocket.send(response);
StringBuilder sb2 = new StringBuilder(); //
for (byte k : newCache) { //
sb2.append(String.format("%02X ", k)); //just for checking the data , will be removed in final version
} //
System.out.println("Sent: " + sb2.toString()); //
}
@Override
protected void compute() {
try {
invokeAll(new Switch(mSocket));
} catch (UnknownHostException ex) {
Logger.getLogger(CwStreamSwitcher.class.getName()).log(Level.SEVERE, null, ex);
} catch (IOException ex) {
Logger.getLogger(CwStreamSwitcher.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
public void CwServer(int port) throws SocketException, IOException {
DatagramSocket serverSocket = new DatagramSocket(port);
int processors = Runtime.getRuntime().availableProcessors();
CwStreamSwitcher.Switch fb = new CwStreamSwitcher.Switch(serverSocket);
ForkJoinPool pool = new ForkJoinPool();
pool.invoke(fb);
}
public static void main(String[] args) throws SocketException, IOException {
int port;
if (args.length > 0) {
port = Integer.parseInt(args[0]);
} else {
port = 9876;
}
new CwStreamSwitcher().CwServer(port);
}
}
该程序编译并运行良好，但大约 5 分钟后它停止并显示以下错误消息：
Exception in thread "main" java.lang.StackOverflowError
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:525)
at java.util.concurrent.ForkJoinTask.getThrowableException(ForkJoinTask.java:536)
at java.util.concurrent.ForkJoinTask.reportResult(ForkJoinTask.java:596)
at java.util.concurrent.ForkJoinTask.join(ForkJoinTask.java:640)
at java.util.concurrent.ForkJoinPool.invoke(ForkJoinPool.java:1521)
at cwstreamswitcher.CwStreamSwitcher.CwServer(CwStreamSwitcher.java:150)
at cwstreamswitcher.CwStreamSwitcher.main(CwStreamSwitcher.java:171)
Caused by: java.lang.StackOverflowError
at java.net.PlainDatagramSocketImpl.receive0(Native Method)
at java.net.AbstractPlainDatagramSocketImpl.receive(AbstractPlainDatagramSocketImpl.java:135)
at java.net.DatagramSocket.receive(DatagramSocket.java:775)
at cwstreamswitcher.CwStreamSwitcher$Switch.<init>(CwStreamSwitcher.java:31)
at cwstreamswitcher.CwStreamSwitcher$Switch.compute(CwStreamSwitcher.java:126)
at java.util.concurrent.RecursiveAction.exec(RecursiveAction.java:177)
at java.util.concurrent.ForkJoinTask.doInvoke(ForkJoinTask.java:377)
at java.util.concurrent.ForkJoinTask.invokeAll(ForkJoinTask.java:721)
CwStreamSwitcher.java:126 是这个方法调用：protected void compute() {
什么会导致这种情况？