我正在开发一个涉及套接字通信的Java应用程序，我正在尝试创建一个Thread子类，将其称为CommandThread，它从套接字读取命令。有效命令包括“DELAY n”和“QUIT”。
我有一些问题和疑虑：
如何改进 processCommand 方法中的错误处理？ 有没有更好的方法来构建从套接字读取和处理命令的代码？ 关于在多线程环境中处理套接字的最佳实践有什么一般建议吗？ 我感谢您提供的任何见解、建议或更正！谢谢你。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class CommandThread extends Thread {
private final Socket clientSocket;
private boolean isRunning;
public CommandThread(Socket clientSocket) {
this.clientSocket = clientSocket;
this.isRunning = true;
}
@Override
public void run() {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
PrintWriter writer = new PrintWriter(clientSocket.getOutputStream(), true);
while (isRunning) {
String command = reader.readLine();
if (command != null) {
processCommand(command, writer);
}
}
// Clean up resources
reader.close();
writer.close();
clientSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private void processCommand(String command, PrintWriter writer) {
if (command.startsWith("DELAY ")) {
try {
int delayTime = Integer.parseInt(command.substring(6));
Thread.sleep(delayTime);
writer.println("OK");
} catch (InterruptedException | NumberFormatException e) {
writer.println("ERROR");
}
} else if (command.equals("QUIT")) {
writer.println("BYE");
isRunning = false;
} else {
writer.println("INVALID COMMAND");
}
}
public static void main(String[] args) {
// Usage example:
// In your server code, when a new client connects, create a CommandThread for that client.
// CommandThread commandThread = new CommandThread(clientSocket);
// commandThread.start();
}
}
如何改进 processCommand 方法中的错误处理？
使用
try-with-resources是否有更好的方法来构造从套接字读取和处理命令的代码？关于在多线程环境中处理套接字的最佳实践有什么一般建议吗？
使用线程池而不是新建线程，这样可以更好地重用服务器资源
public class CommandHandler implements Runnable {
private final Socket clientSocket;
private boolean isRunning;
public CommandHandler(Socket clientSocket) {
this.clientSocket = clientSocket;
this.isRunning = true;
}
@Override
public void run() {
try (Socket socket = clientSocket;
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintWriter writer = new PrintWriter(socket.getOutputStream(), true)) {
while (isRunning) {
String command = reader.readLine();
if (command != null) {
String result = processCommand(command);
writer.println(result);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
private String processCommand(String command) {
if (command.startsWith("DELAY ")) {
try {
int delayTime = Integer.parseInt(command.substring(6));
Thread.sleep(delayTime);
return "OK";
} catch (InterruptedException | NumberFormatException e) {
return "ERROR";
}
} else if (command.equals("QUIT")) {
isRunning = false;
return "BYE";
} else {
return "INVALID COMMAND";
}
}
public static void main(String[] args) {
// Usage example:
/*
// global thread pool
ThreadPoolExecutor executor = new ThreadPoolExecutor(20, 40,
0L, TimeUnit.MILLISECONDS,
new ArrayBlockingQueue<>(500));
ServerSocket serverSocket = new ServerSocket(8080);
while (true) {
Socket clientSocket = serverSocket.accept();
CommandHandler commandHandler = new CommandHandler(clientSocket);
executor.execute(commandHandler);
}
*/
}
}
您的代码是用BIO模式编写的，使用NIO或AIO可以获得更好的性能。
使用Reactor模式来编写你的代码，你可以从Netty学习更多内容[https://netty.io/index.html]。
这是一个用 Java nio 编写的简单示例，如果使用 Netty 可以做得更好。
public class ServerSocketTest {
/**
* server ip
*/
private final String HOST = "127.0.0.1";
/**
* server port
*/
private final int PORT = 8080;
@Test
public void testServer() throws IOException {
// create Selector
Selector selector = Selector.open();
// create ServerSocketChannel and listen port
ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
serverSocketChannel.socket().bind(new InetSocketAddress(PORT));
serverSocketChannel.configureBlocking(false);
// register Channel
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
// create buffer
ByteBuffer buffer = ByteBuffer.allocate(1024);
Charset charset = StandardCharsets.UTF_8;
CharsetDecoder charsetDecoder = charset.newDecoder();
CharBuffer charBuffer = CharBuffer.allocate(1024);
while (true) {
// block and wait
if (selector.select() == 0) {
continue;
}
// get ready Channel set
Set<SelectionKey> selectionKeys = selector.selectedKeys();
Iterator<SelectionKey> iterator = selectionKeys.iterator();
while (iterator.hasNext()) {
SelectionKey key = iterator.next();
// remove current key from set
iterator.remove();
// if read event
if (key.isAcceptable()) {
ServerSocketChannel server = (ServerSocketChannel) key.channel();
// accept connection from client
SocketChannel clientChannel = server.accept();
clientChannel.configureBlocking(false);
// register with Selector，wait for connections
clientChannel.register(selector, SelectionKey.OP_READ);
System.out.println("Accepted connection from " + clientChannel);
}
// if read event
if (key.isReadable()) {
SocketChannel clientChannel = (SocketChannel) key.channel();
buffer.clear();
// read data
StringBuilder stringBuilder = new StringBuilder();
while (clientChannel.read(buffer) != -1 || buffer.position() != 0) {
buffer.flip();
charsetDecoder.decode(buffer, charBuffer, true);
charBuffer.flip();
stringBuilder.append(charBuffer);
charBuffer.clear();
buffer.compact();
}
String message = stringBuilder.toString();
System.out.println("Received message from " + clientChannel + ": " + message);
// write data back
clientChannel.write(charset.encode("Echo: " + message));
// client close connection
clientChannel.close();
}
}
}
}
@Test
public void testClient() {
ByteBuffer byteBuffer = ByteBuffer.allocate(8192);
Charset charset = StandardCharsets.UTF_8;
CharsetDecoder charsetDecoder = charset.newDecoder();
// connect server
try (SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress(HOST, PORT))) {
// send message to server
byteBuffer.put(charset.encode("hello server"));
byteBuffer.flip();
socketChannel.write(byteBuffer);
socketChannel.shutdownOutput();
byteBuffer.clear();
// receive response from server
StringBuilder stringBuilder = new StringBuilder();
while (socketChannel.read(byteBuffer) != -1 || byteBuffer.position() != 0) {
byteBuffer.flip();
// decode and store
CharBuffer decode = charsetDecoder.decode(byteBuffer);
stringBuilder.append(decode);
byteBuffer.compact();
}
System.out.println("Received message from server " + socketChannel + ": " + stringBuilder);
} catch (IOException e) {
Assert.fail();
}
}
}