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解决跨域（CORS）问题
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为什么会有跨域问题
是因为浏览器的同源策略是对ajax请求进行阻拦了，但是不是所有的请求都给做跨域，像是一般的href属性，a标签什么的都不拦截
解决跨域问题的两种方式
-
JSONP 推荐参考
-
CORS
JSONP
先简单来说一下JSONP，具体详细详见上面JSONP
JSONP是json用来跨域的一个东西。原理是通过script标签的跨域特性来绕过同源策略。（创建一个回调函数，然后在远程服务上调用这个函数并且将json数据形式作为参数传递，完成回调）。
CORS跨域
随着技术的发展，现在的浏览器可以主动支持设置从而允许跨域请求，即：跨域资源共享（CORS，Cross-Origin Resource Sharing），其本质是设置响应头，使得浏览器允许跨域请求。
1、简单请求和复杂请求
条件：
1、请求方式：HEAD、GET、POST
2、请求头信息：
Accept
Accept-Language
Content-Language
Last-Event-ID
Content-Type 对应的值是以下三个中的任意一个
application/x-www-form-urlencoded
multipart/form-data
text/plain 注意：同时满足以上两个条件时，则是简单请求，否则为复杂请求
2、简单请求和复杂请求的区别？
简单请求：一次请求
非简单请求：两次请求，在发送数据之前会先发第一次请求做‘预检’，只有‘预检’通过后才再发送一次请求用于数据传输。
3、关于预检
- 请求方式：OPTIONS
- “预检”其实做检查，检查如果通过则允许传输数据，检查不通过则不再发送真正想要发送的消息
- 如何“预检”
=> 如果复杂请求是PUT等请求，则服务端需要设置允许某请求，否则“预检”不通过
Access-Control-Request-Method
=> 如果复杂请求设置了请求头，则服务端需要设置允许某请求头，否则“预检”不通过
Access-Control-Request-Headers
4、CORS的优缺点
- CORS的优点：可以发任意请求
- CORS的缺点：上是复杂请求的时候得先做个预检，再发真实的请求。发了两次请求会有性能上的损耗
JSONP和CORS的区别
JSONP：服务端不用修改，需要改前端。发jsonp请求
JSONP：只能发GET请求
CORS：前端的代码不用修改，服务端的代码需要修改。如果是简单请求的话在服务端加上一个响应头。
CORS：可以发任意请求
基于CORS实现ajax请求
1、支持跨域，简单请求
客户端
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width">
<title>Title</title>
</head>
<body>
<div>
<h1>欢迎来到我的主页</h1>
<button onclick="getData()">获取用户数据</button>
</div>
<script src="/static/jquery-1.12.4.min.js"></script>
<script>
function getData() {
$.ajax({
url:'http://127.0.0.1:8080/index/',
type:"GET",
success:function (data) {
console.log(data)
} })
}
</script>
</body>
</html>
服务端
from django.shortcuts import render
from django.http import JsonResponse
from rest_framework.views import APIView # Create your views here.
class IndexView(APIView):
def get(self,request,*args,**kwargs):
ret = {
'code': 111,
'data': '你好吗？'
}
response = JsonResponse(ret)
response['Access-Control-Allow-Origin'] = "*"
return response
2、支持跨域，复杂请求
如果是复杂请求在你真正的发请求之前，会先偷偷的发一个OPTION请求，先预检一下，我
允许你来你才来
如果想预检通过就得写个option请求
客户端
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width">
<title>Title</title>
</head>
<body>
<input type="button" value="获取用户数据" onclick="getUser()">
<script src="/static/jquery-1.12.4.min.js"></script>
<script>
function getUser() {
$.ajax({
url:'http://127.0.0.1:8080/user/',
type:'POST',
data:{'k1':'v1'},
headers:{
'h1':'sdfdgfdg'
},
success:function (ret) {
console.log(ret)
}
})
}
</script>
</body>
</html>
服务端
from django.shortcuts import render,HttpResponse
from django.http import JsonResponse
from rest_framework.views import APIView class UserIndex(APIView):
def get(self,request,*args,**kwargs):
ret = {
'code': 111,
'data': '你好吗？'
}
response = JsonResponse(ret)
response['Access-Control-Allow-Origin'] = "*"
return response def post(self,request,*args,**kwargs):
print(request.POST.get('k1'))
ret = {
'code':1000,
'data':'过年啦',
}
response = JsonResponse(ret)
response['Access-Control-Allow-Origin'] = "*"
return response def options(self, request, *args, **kwargs):
# self.set_header('Access-Control-Allow-Origin', "http://www.xxx.com")
# self.set_header('Access-Control-Allow-Headers', "k1,k2")
# self.set_header('Access-Control-Allow-Methods', "PUT,DELETE")
# self.set_header('Access-Control-Max-Age', 10) response = HttpResponse()
response['Access-Control-Allow-Origin'] = '*'
response['Access-Control-Allow-Headers'] = 'h1'
# response['Access-Control-Allow-Methods'] = 'PUT'
return response
由于复杂请求时，首先会发送“预检”请求，如果“预检”成功，则发送真实数据。
- “预检”请求时，允许请求方式则需服务器设置响应头：Access-Control-Request-Method
- “预检”请求时，允许请求头则需服务器设置响应头：Access-Control-Request-Headers
- “预检”缓存时间，服务器设置响应头：Access-Control-Max-Age
3、跨域获取响应头
默认获取到的所有响应头只有基本信息，如果想要获取自定义的响应头，则需要再服务器端设置Access-Control-Expose-Headers
客户端
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body> <p>
<input type="submit" onclick="XmlSendRequest();" />
</p> <p>
<input type="submit" onclick="JqSendRequest();" />
</p> <script type="text/javascript" src="jquery-1.12.4.js"></script>
<script>
function XmlSendRequest(){
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function(){
if(xhr.readyState == 4) {
var result = xhr.responseText;
console.log(result);
// 获取响应头
console.log(xhr.getAllResponseHeaders());
}
};
xhr.open('PUT', "http://c2.com:8000/test/", true);
xhr.setRequestHeader('k1', 'v1');
xhr.send();
} function JqSendRequest(){
$.ajax({
url: "http://c2.com:8000/test/",
type: 'PUT',
dataType: 'text',
headers: {'k1': 'v1'},
success: function(data, statusText, xmlHttpRequest){
console.log(data);
// 获取响应头
console.log(xmlHttpRequest.getAllResponseHeaders());
}
})
} </script>
</body>
</html> HTML
服务端
class MainHandler(tornado.web.RequestHandler):
def put(self):
self.set_header('Access-Control-Allow-Origin', "http://www.xxx.com")
self.set_header('xxoo', "seven")
self.set_header('bili', "daobidao")
self.set_header('Access-Control-Expose-Headers', "xxoo,bili")
self.write('{"status": true, "data": "seven"}')
def options(self, *args, **kwargs):
self.set_header('Access-Control-Allow-Origin', "http://www.xxx.com")
self.set_header('Access-Control-Allow-Headers', "k1,k2")
self.set_header('Access-Control-Allow-Methods', "PUT,DELETE")
self.set_header('Access-Control-Max-Age', 10)
Tornado
4、跨域传输cookie
在跨域请求中，默认情况下，HTTP Authentication信息，Cookie头以及用户的SSL证书无论在预检请求中或是在实际请求都是不会被发送。
如果想要发送：
- 浏览器端：XMLHttpRequest的withCredentials为true
- 服务器端：Access-Control-Allow-Credentials为true
- 注意：服务器端响应的 Access-Control-Allow-Origin 不能是通配符 *
客户端 浏览器html
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body> <p>
<input type="submit" onclick="XmlSendRequest();" />
</p> <p>
<input type="submit" onclick="JqSendRequest();" />
</p> <script type="text/javascript" src="jquery-1.12.4.js"></script>
<script>
function XmlSendRequest(){
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function(){
if(xhr.readyState == 4) {
var result = xhr.responseText;
console.log(result);
}
}; xhr.withCredentials = true; xhr.open('PUT', "http://c2.com:8000/test/", true);
xhr.setRequestHeader('k1', 'v1');
xhr.send();
} function JqSendRequest(){
$.ajax({
url: "http://c2.com:8000/test/",
type: 'PUT',
dataType: 'text',
headers: {'k1': 'v1'},
xhrFields:{withCredentials: true},
success: function(data, statusText, xmlHttpRequest){
console.log(data);
}
})
} </script>
</body>
</html> HTML
服务端视图
class MainHandler(tornado.web.RequestHandler):
def put(self):
self.set_header('Access-Control-Allow-Origin', "http://www.xxx.com")
self.set_header('Access-Control-Allow-Credentials', "true")
self.set_header('xxoo', "seven")
self.set_header('bili', "daobidao")
self.set_header('Access-Control-Expose-Headers', "xxoo,bili")
self.set_cookie('kkkkk', 'vvvvv');
self.write('{"status": true, "data": "seven"}')
def options(self, *args, **kwargs):
self.set_header('Access-Control-Allow-Origin', "http://www.xxx.com")
self.set_header('Access-Control-Allow-Headers', "k1,k2")
self.set_header('Access-Control-Allow-Methods', "PUT,DELETE")
self.set_header('Access-Control-Max-Age', 10)
在Django中间件中解决跨域问题
class MiddlewareMixin(object):
def __init__(self, get_response=None):
self.get_response = get_response
super(MiddlewareMixin, self).__init__()
def __call__(self, request):
response = None
if hasattr(self, 'process_request'):
response = self.process_request(request)
if not response:
response = self.get_response(request)
if hasattr(self, 'process_response'):
response = self.process_response(request, response)
return response
class CORSMiddleware(MiddlewareMixin):
def process_response(self,request,response):
# 添加响应头
# 允许你的域名来获取我的数据
# response['Access-Control-Allow-Origin'] = "*"
# 允许你携带Content-Type请求头
# response['Access-Control-Allow-Headers'] = "Content-Type"
# 允许你发送DELETE,PUT
# response['Access-Control-Allow-Methods'] = "DELETE,PUT"
response['Access-Control-Allow-Origin'] = "*"
if request.method == "OPTIONS":
response['Access-Control-Allow-Headers'] = "Content-Type"
response['Access-Control-Allow-Methods'] = "PUT,DELETE"
return response
class MiddlewareMixin(object):
def __init__(self, get_response=None):
self.get_response = get_response
super(MiddlewareMixin, self).__init__() def __call__(self, request):
response = None
if hasattr(self, 'process_request'):
response = self.process_request(request)
if not response:
response = self.get_response(request)
if hasattr(self, 'process_response'):
response = self.process_response(request, response)
return response class CORSMiddleware(MiddlewareMixin):
def process_response(self,request,response):
# 添加响应头
# 允许你的域名来获取我的数据
# response['Access-Control-Allow-Origin'] = "*"
# 允许你携带Content-Type请求头
# response['Access-Control-Allow-Headers'] = "Content-Type"
# 允许你发送DELETE,PUT
# response['Access-Control-Allow-Methods'] = "DELETE,PUT"
response['Access-Control-Allow-Origin'] = "*"
if request.method == "OPTIONS":
response['Access-Control-Allow-Headers'] = "Content-Type"
response['Access-Control-Allow-Methods'] = "PUT,DELETE"
return response
