此篇文章使用的是spring 包下的类来实现简单的Java websocket 服务端和客户端。

1 引入包依赖

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
        </dependency>

码云地址

2 创建服务端

2.1 注册端点

创建服务端很简单，使用@EnableWebSocket注解声明使用websocket，实现WebSocketConfigurer，在WebSocketHandlerRegistry的addHandler方法中添加消息处理的handler以及端点，其作用和@ServerEndpoint类似。

@Configuration
@EnableWebSocket
public class ServerConfig implements WebSocketConfigurer {
    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry webSocketHandlerRegistry) {
        webSocketHandlerRegistry.addHandler(new ServerHandler(),"/sp");
        webSocketHandlerRegistry.addHandler(new ServerHandler2(),"/sp2");
    }
}

2.2 消息处理handler

继承AbstractWebSocketHandler，可以处理收到文本、二进制、ping消息；如果只有文本消息，可以继承TextWebSocketHandler；如果只有二进制消息，可以继承BinaryWebSocketHandler。
handler的处理方法可以与tomcat包的注解做个对比：

public class ServerHandler extends AbstractWebSocketHandler {
    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        System.out.println(session.getId() + "客户连接");
    }

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        System.out.println("收到文本消息" + session.getId() + ":" + message.getPayload());
        //发送数据给客户端
        session.sendMessage(new TextMessage("服务端收到：" + message.getPayload()));
    }

    @Override
    protected void handleBinaryMessage(WebSocketSession session, BinaryMessage message) throws Exception {
        System.out.println("二进制消息");
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        System.out.println(session.getId() + "关闭连接");
    }

    @Override
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        System.out.println(session.getId() + "发生错误");
        exception.printStackTrace();
    }
}

2.3 拦截器

可以在客户端与服务端连接成功前后做拦截，拦截器继承HttpSessionHandshakeInterceptor，并添加到WebSocketHandlerRegistry，拦截器添加在哪个端点，就会只拦截哪个端点的。
拦截器实现：

public class ServerInterceptor extends HttpSessionHandshakeInterceptor {
    @Override
    public boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception {
        //获取端点携带的参数
        String name = ((ServletServerHttpRequest) request).getServletRequest().getParameter("name");
        System.out.println("before name="+name);
        return super.beforeHandshake(request, response, wsHandler, attributes);
    }

    @Override
    public void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Exception ex) {
        String name = ((ServletServerHttpRequest) request).getServletRequest().getParameter("name");
        System.out.println("after name="+name);
        super.afterHandshake(request, response, wsHandler, ex);
    }
}

端点注册添加拦截器，ServerInterceptor只对/sp起作用，ServerInterceptor2对/sp2起作用。

@Configuration
@EnableWebSocket
public class ServerConfig implements WebSocketConfigurer {
    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry webSocketHandlerRegistry) {
        webSocketHandlerRegistry.addHandler(new ServerHandler(),"/sp").addInterceptors(new ServerInterceptor());
        webSocketHandlerRegistry.addHandler(new ServerHandler2(),"/sp2").addInterceptors(new ServerInterceptor2());
    }
}

3 创建客户端

3.1 实现客户端handler

客户端也是继承AbstractWebSocketHandler实现消息处理。

public class ClientHandler extends AbstractWebSocketHandler {
    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        System.out.println(session.getId()+"客户连接");
    }

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        System.out.println("收到文本消息" + session.getId() + ":" + message.getPayload());
    }

    @Override
    protected void handleBinaryMessage(WebSocketSession session, BinaryMessage message) throws Exception {
        System.out.println("二进制消息");
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        System.out.println(session.getId() + "关闭连接");
    }
}

public class Client  {
    public static void main(String[] args) {
        StandardWebSocketClient client = new StandardWebSocketClient();
        ClientHandler handler = new ClientHandler();
        //连接带参数
        String url = "ws://localhost:8080/sp2?name=quit";
        ListenableFuture<WebSocketSession> future = client.doHandshake(handler,url);
        try (WebSocketSession session = future.get()){
            session.sendMessage(new TextMessage("发送数据111"));
            session.sendMessage(new TextMessage("发送数据2222"));
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}