java websocket实现长连接 附加代码实现

Java中实现Websocket长连接可以使用Java API中提供的javax.websocket.*类库，下面是一个简单的示例代码：

Server端：

import java.io.IOException;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint("/websocket")
public class WebSocketServer {

    @OnOpen
    public void onOpen(Session session) {
        System.out.println("Websocket connection opened: " + session.getId());
    }

    @OnMessage
    public void onMessage(String message, Session session) throws IOException {
        System.out.println("Received message: " + message);
        session.getBasicRemote().sendText("Server received: " + message);
    }

    @OnClose
    public void onClose(Session session) {
        System.out.println("Websocket connection closed: " + session.getId());
    }

    @OnError
    public void onError(Throwable t) {
        System.out.println("Websocket error: " + t.getMessage());
    }
}

Client端：

import java.net.URI;
import java.net.URISyntaxException;
import java.util.concurrent.CountDownLatch;
import javax.websocket.ClientEndpoint;
import javax.websocket.CloseReason;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.WebSocketContainer;

@ClientEndpoint
public class WebSocketClient {

    private final CountDownLatch latch;

    public WebSocketClient() {
        latch = new CountDownLatch(1);
    }

    public void connect(String uri) throws URISyntaxException, InterruptedException {
        WebSocketContainer container = ContainerProvider.getWebSocketContainer();
        container.connectToServer(this, new URI(uri));
        latch.await();
    }

    @OnOpen
    public void onOpen(Session session) {
        System.out.println("Websocket connection opened: " + session.getId());
    }

    @OnMessage
    public void onMessage(String message, Session session) {
        System.out.println("Received message: " + message);
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
        System.out.println("Websocket connection closed: " + session.getId() + ", reason: " + closeReason.getReasonPhrase());
        latch.countDown();
    }

    @OnError
    public void onError(Throwable t) {
        System.out.println("Websocket error: " + t.getMessage());
        latch.countDown();
    }
}

这里以Java API提供的javax.websocket.*类库为例，客户端和服务端的代码都非常简单明了。

服务端使用@ServerEndpoint注解标识一个类作为WebSocket服务器端点。在该类中，通过@OnOpen、@OnMessage、@OnClose和@OnError注解定义了WebSocket连接打开、接收消息、连接关闭以及发生错误时的处理逻辑。

客户端则使用@ClientEndpoint注解标识一个类作为WebSocket客户端端点。在该类中，通过@OnOpen、@OnMessage、@OnClose和@OnError注解定义了WebSocket连接打开、接收消息、连接关闭以及发生错误时的处理逻辑。在connect方法中通过WebSocketContainer.connectToServer方法连接到服务端，并通过CountDownLatch来保证连接成功后代码的运行。