has been blocked by CORS policy: Response to preflight request doesn't pass access control check: The value of the 'Access-Control-Allow-Credentials' header in the response is '' which must be 'true' when the request's credentials mode is 'include'. The credentials mode of requests initiated by the XMLHttpRequest is controlled by the withCredentials attribute.Java应该用代码怎么解决
时间: 2023-11-27 19:53:17 浏览: 25
这个问题是由于浏览器的跨域安全策略引起的。在JavaScript中,如果你使用XMLHttpRequest发送跨域请求并且要发送cookies或认证信息,那么请求会被浏览器阻止,并显示类似"has been blocked by CORS policy"的错误。
为了解决这个问题,你需要在服务端设置响应头Access-Control-Allow-Credentials为true。具体的代码实现取决于你所使用的服务器框架和语言。下面是一个Java Spring Boot框架的示例代码:
```java
@RestController
public class MyController {
@CrossOrigin(value = "*", allowCredentials = "true")
@GetMapping("/myEndpoint")
public ResponseEntity<String> myEndpoint() {
// your endpoint logic here
return ResponseEntity.ok("success");
}
}
```
在这个示例中,@CrossOrigin注解用于设置跨域访问的配置,在value参数中设置"*"表示允许所有来源进行跨域访问,allowCredentials设置为"true"表示允许发送cookies或认证信息。
注意:在设置Access-Control-Allow-Credentials为true时,Access-Control-Allow-Origin不能设置为通配符"*",必须指定具体的来源。