个人Websocket学习使用总结
主要参考了这篇文章：https://www.cnblogs.com/freud/p/8397934.html
1.客户端
var websocket = null;
var host = document.location.host;
var userid = "${user.id}"; // 获得当前登录人员的id
//判断当前浏览器是否支持WebSocket
if ('WebSocket' in window) {
websocket = new WebSocket('ws://'+host+'/iats/webSocket/?userid='+userid);
} else {
alert('当前浏览器不支持websocket')
}
//连接发生错误的回调方法
websocket.onerror = function() {
setMessageInnerHTML("WebSocket连接发生错误");
};
//连接成功建立的回调方法
websocket.onopen = function() {
setMessageInnerHTML("WebSocket连接成功");
}
//接收到消息的回调方法
websocket.onmessage = function(event) {
alert("接收到消息的回调方法")
alert("这是后台推送的消息："+event.data);
websocket.close();
alert("webSocket已关闭！")
}
//连接关闭的回调方法
websocket.onclose = function() {
setMessageInnerHTML("WebSocket连接关闭");
}
//监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。
window.onbeforeunload = function() {
closeWebSocket();
}
//关闭WebSocket连接
function closeWebSocket() {
websocket.close();
}
//将消息显示在网页上
function setMessageInnerHTML(innerHTML) {
document.getElementById('message').innerHTML += innerHTML + '
';
}2.服务端
import java.io.IOException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import com.alibaba.fastjson.JSONObject;
@ServerEndpoint("/webSocket/")
public class WebSocket {
private static int onlineCount = 0;
private static Map clients = new ConcurrentHashMap();
private Session session;
private String userid;
@OnOpen
public void onOpen(@PathParam("userid") String userid, Session session) throws IOException {
this.userid = userid;
this.session = session;
addOnlineCount();
clients.put(userid, this);
System.out.println("已连接");
}
@OnClose
public void onClose() throws IOException {
clients.remove(userid);
subOnlineCount();
}
@OnMessage
public void onMessage(String message) throws IOException {
JSONObject jsonTo = JSONObject.parseObject(message);
String mes = (String) jsonTo.get("message");
if (!jsonTo.get("To").equals("All")){
sendMessageTo(mes, jsonTo.get("To").toString());
}else{
sendMessageAll("给所有人");
}
}
@OnError
public void onError(Session session, Throwable error) {
error.printStackTrace();
}
public void sendMessageTo(String message, String To) throws IOException {
// session.getBasicRemote().sendText(message);
//session.getAsyncRemote().sendText(message);
for (WebSocket item : clients.values()) {
if (item.userid.equals(To) )
item.session.getAsyncRemote().sendText(message);
}
}
public void sendMessageAll(String message) throws IOException {
for (WebSocket item : clients.values()) {
item.session.getAsyncRemote().sendText(message);
}
}
public static synchronized int getOnlineCount() {
return onlineCount;
}
public static synchronized void addOnlineCount() {
WebSocket.onlineCount++;
}
public static synchronized void subOnlineCount() {
WebSocket.onlineCount--;
}
public static synchronized Map getClients() {
return clients;
} 3.调用
WebSocket ws = new WebSocket();
JSONObject jo = new JSONObject();
jo.put("message", "这是后台返回的消息！");
jo.put("To", UserUtils.getUser().getId());
ws.onMessage(jo.toString());4.遇到的问题
- 连接失败，报404错误：WebSocket connection to 'ws://localhost:8080/iats/websocket/?userid=1' failed: Error during WebSocket handshake: Unexpected response code: 404
web容器换成tomcat就行了，参考文章：https://www.oschina.net/question/1756518_238747
- 服务端接收不到客户端传过来的参数，传过来的userid为null
本来以为websocket可以和http协议一样传参，于是这样写了：
websocket = new WebSocket('ws://'+host+'/iats/webSocket/?userid='+userid); 然而不能这样传，改成这样就行了
客户端：
websocket = new WebSocket('ws://'+host+'/iats/webSocket/'+userid); 服务端：
@ServerEndpoint("/webSocket/{userid}") 传多个参：
websocket = new WebSocket('ws://'+host+'/iats/webSocket/'+userid+'/'+param); @ServerEndpoint("/webSocket/{userid}/{param}") public void onOpen(@PathParam("userid") String userid, @PathParam("param") String param, Session session) throws IOException {- 推送时后台报错：The remote endpoint was in state [TEXT_FULL_WRITING] which is an invalid state for called method
产生原因貌似是：发送数据频繁而导致发送重叠。 我的websocket使用场景是自动化测试中，对代码进行分析，将分析日志同步推送到页面展示。所以确实会每秒推送大量信息。
解决方案：
item.session.getAsyncRemote().sendText(message); 改为
item.session.getBasicRemote().sendText(message);