报错：

Error during WebSocket handshake: Unexpected response code: 404

Connection closed before receiving a handshake response

结论：

OpOpen、OnMessage...包导错了!!!  

BeforeHandshake时由于逻辑原因导致session.close()

连接路径未加上context-path

详解

1. 报错404原因

报错

Error during WebSocket handshake: Unexpected response code: 404

代码中导入的包

import org.yeauty.annotation.*;

import javax.websocket.OnOpen;
import javax.websocket.OnMessage;
import javax.websocket.OnClose;
import javax.websocket.OnError;

虽然已经导入了第一行，但是如果也一起导入下面的几行，系统会优先使用下面的注解，导致Unexpected response code: 404错误

为写context-path也会导致404错误

2.连接失败原因

报错

Connection closed before receiving a handshake response

在代码中，如果在BeforeHandshake中调用了session.close()，便会导致如上报错