背景
- 在实际项目中，可能会通过前端框架使用 WebSocket 和后端进行通信
- 这里就来详细讲解下 FastAPI 是如何操作 WebSocket 的
模拟 WebSocket 客户端
代码语言：javascript复制#!usr/bin/env python
# -*- coding:utf-8 _*-
"""
# author: 小菠萝测试笔记
# blog: https://www.cnblogs.com/poloyy/
# time: 2021/10/5 5:26 下午
# file: 46_websocket.py
"""
import uvicorn
from fastapi import FastAPI, WebSocket
from fastapi.responses import HTMLResponse
app = FastAPI()
html = """
<!DOCTYPE html>
<html>
<head>
<title>小菠萝聊天室</title>
</head>
<body>
<h1>小菠萝聊天室</h1>
<form action="" onsubmit="sendMessage(event)">
<input type="text" id="messageText" autocomplete="off"/>
<button>Send</button>
</form>
<ul id='messages'>
</ul>
<script>
// 加载页面，自动创建一个 WebSocket 连接
var ws = new WebSocket("ws://localhost:8080/ws");
// 收到消息
ws.onmessage = function(event) {
// 获取输入框的值
var messages = document.getElementById('messages')
// 创建一个 li 元素
var message = document.createElement('li')
// 接收 event 的 data
var content = document.createTextNode(event.data)
message.appendChild(content)
messages.appendChild(message)
};
// 发送消息方法
function sendMessage(event) {
var input = document.getElementById("messageText")
ws.send(input.value)
input.value = ''
event.preventDefault()
}
</script>
</body>
</html>
"""
# 返回一段 HTML 代码给前端
@app.get("/")
async def get():
return HTMLResponse(html)
@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
# 1、ws 连接
await websocket.accept()
while True:
# 2、接收客户端发送的内容
data = await websocket.receive_text()
# 3、服务端发送内容
await websocket.send_text(f"小菠萝收到的消息是: {data}")
if __name__ == '__main__':
uvicorn.run(app="46_websocket:app", reload=True, host="127.0.0.1", port=8080)启动 uvicorn 服务器，访问 127.0.0.1:8080/
客户端、服务端建立 WebSocket 连接成功
发送聊天信息
每发一条消息，均会显示在列表中
可以在其他地方使用 WebSocket
- Depends
- Security
- Cookie
- Header
- Path
- Query
在依赖项中使用 WebSocket
代码语言：javascript复制from typing import Optional
import uvicorn
from fastapi import FastAPI, WebSocket, Cookie, Query, status, Depends
from fastapi.responses import HTMLResponse
app = FastAPI()
html = """
<!DOCTYPE html>
<html>
<head>
<title>Chat</title>
</head>
<body>
<h1>小菠萝聊天室</h1>
<form action="" onsubmit="sendMessage(event)">
<label>Item ID: <input type="text" id="itemId" autocomplete="off" value="foo"/></label>
<label>Token: <input type="text" id="token" autocomplete="off" value="some-key-token"/></label>
<button onclick="connect(event)">Connect</button>
<hr>
<label>Message: <input type="text" id="messageText" autocomplete="off"/></label>
<button>Send</button>
</form>
<ul id='messages'>
</ul>
<script>
var ws = null;
function connect(event) {
var itemId = document.getElementById("itemId")
var token = document.getElementById("token")
ws = new WebSocket("ws://localhost:8080/items/" itemId.value "/ws?token=" token.value);
ws.onmessage = function(event) {
var messages = document.getElementById('messages')
var message = document.createElement('li')
var content = document.createTextNode(event.data)
message.appendChild(content)
messages.appendChild(message)
};
event.preventDefault()
}
function sendMessage(event) {
var input = document.getElementById("messageText")
ws.send(input.value)
input.value = ''
event.preventDefault()
}
</script>
</body>
</html>
"""
@app.get("/")
async def get():
return HTMLResponse(html)
async def get_cookie_or_token(
websocket: WebSocket,
session: Optional[str] = Cookie(None),
token: Optional[str] = Query(None)
):
# 模拟：如果 session 和 token 都为空，则关闭 websocket
if session or token:
return session or token
await websocket.close(code=status.WS_1008_POLICY_VIOLATION)
@app.websocket("/items/{item_id}/ws")
async def websocket_depends(
websocket: WebSocket,
item_id: str,
q: Optional[str] = None,
# 依赖项
cookie_or_token: str = Depends(get_cookie_or_token)
):
# 1、创建 websocket 连接
await websocket.accept()
while True:
# 2、接收客户端发送的内容
data = await websocket.receive_text()
# 3、服务端发送内容
await websocket.send_text(f"cookie or token value is:{cookie_or_token}")
if q:
# 4、如果有传查询参数 q，则再发一条
await websocket.send_text(f"query param value is:{q}")
# 5、最后再发一条信息
await websocket.send_text(f"Message text was: {data}, for item ID: {item_id}")
if __name__ == '__main__':
uvicorn.run(app="46_websocket:app", reload=True, host="127.0.0.1", port=8080)发送聊天信息
不带查询参数 q
带查询参数 q
当 WebSocket 连接关闭时
await websocket.receive_text() 将引发 WebSocketDisconnect 异常，这不是期望看到的结果
处理断开连接和多个客户端
代码语言：javascript复制from typing import List
import uvicorn
from fastapi import FastAPI, WebSocket, WebSocketDisconnect, status
from fastapi.responses import HTMLResponse
app = FastAPI()
html = """
<!DOCTYPE html>
<html>
<head>
<title>Chat</title>
</head>
<body>
<h1>WebSocket Chat</h1>
<h2>Your ID: <span id="ws-id"></span></h2>
<form action="" onsubmit="sendMessage(event)">
<input type="text" id="messageText" autocomplete="off"/>
<button>Send</button>
</form>
<ul id='messages'>
</ul>
<script>
var client_id = Date.now()
document.querySelector("#ws-id").textContent = client_id;
var ws = new WebSocket(`ws://localhost:8080/ws/${client_id}`);
ws.onmessage = function(event) {
var messages = document.getElementById('messages')
var message = document.createElement('li')
var content = document.createTextNode(event.data)
message.appendChild(content)
messages.appendChild(message)
};
function sendMessage(event) {
var input = document.getElementById("messageText")
ws.send(input.value)
input.value = ''
event.preventDefault()
}
</script>
</body>
</html>
"""
# 返回一段 HTML 代码给前端
@app.get("/")
async def get():
return HTMLResponse(html)
# 处理和广播消息到多个 WebSocket 连接
class ConnectionManager:
def __init__(self):
self.active_connections: List[WebSocket] = []
async def connect(self, websocket: WebSocket):
await websocket.accept()
self.active_connections.append(websocket)
def disconnect(self, websocket: WebSocket):
self.active_connections.remove(websocket)
async def send_personal_message(self, message: str, websocket: WebSocket):
await websocket.send_text(message)
async def broadcast(self, message: str):
for connection in self.active_connections:
await connection.send_text(message)
manager = ConnectionManager()
@app.websocket("/ws/{client_id}")
async def websocket_endpoint(client_id: str, websocket: WebSocket):
# 1、客户端、服务端建立 ws 连接
await manager.connect(websocket)
# 2、广播某个客户端进入聊天室
await manager.broadcast(f"{client_id} 进入了聊天室")
try:
while True:
# 3、服务端接收客户端发送的内容
data = await websocket.receive_text()
# 4、广播某个客户端发送的消息
await manager.broadcast(f"{client_id} 发送消息：{data}")
# 5、服务端回复客户端
await manager.send_personal_message(f"服务端回复{client_id}：你发送的信息是：{data}", websocket)
except WebSocketDisconnect:
# 6、若有客户端断开连接，广播某个客户端离开了
manager.disconnect(websocket)
await manager.broadcast(f"{client_id} 离开了聊天室")
if __name__ == '__main__':
uvicorn.run(app="48_websocket_handler:app", reload=True, host="127.0.0.1", port=8080)- 模拟一个小型聊天室的场景
- 新的客户端进来，所有人都会收到新客户端进入聊天室的消息
- 某个客户端发送消息，所有人都能看到
- 某个客户端退出了（关闭浏览器），所有人都会收到该客户端退出聊天室的消息
浏览器打开三个 tab 均访问 127.0.0.1:8080
关掉其中一个客户端（tab）
