背景
公司网站上线需要一个实时报价功能,于是想到了 Websocket, 我在多年前就尝试过Websocket 那时 HTML5标准尚未产生,各家实现均有不同,Websocket 版本也非常多,实现兼容也比较复杂,于是放弃Websocket。最近看到Websocket 开始流行起来,兼容也不再是障碍。
以下节选自《Netkiller Java 手札》,下面例子实现一个简单的 Echo Server
目录
环境:Java8 + Tomcat8
package websocket;
/**
* Websocket Server
*
* @author netkiller<netkiller@msn.com>
*/
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
@ServerEndpoint(value = "/echo")
public class PriceServer {
private Set<Session> sessions = Collections.synchronizedSet(new HashSet<Session>());
/**
* Callback hook for Connection open events. This method will be invoked
* when a client requests for a WebSocket connection.
*
* @param session
* the session which is opened.
*/
@OnOpen
public void onOpen(Session session) {
sessions.add(session);
}
/**
* Callback hook for Connection close events. This method will be invoked
* when a client closes a WebSocket connection.
*
* @param session
* the session which is opened.
*/
@OnClose
public void onClose(Session session) {
sessions.remove(session);
}
/**
* Callback hook for Message Events. This method will be invoked when a
* client send a message.
*
* @param message
* The text message
* @param session
* The session of the client
*/
@OnMessage
public void onMessage(String message, Session session) {
System.out.println("Message Received: " + message);
for (Session remote : sessions) {
System.out.println("Sending to " + remote.getId());
remote.getAsyncRemote().sendText(message);
}
}
}